Fake background blur on camera-phones

[steve30]

What's the deal with these camera-phones which attempt to fake a shallow depth of field? I'm seeing a lot of photos on the internet where there is fake background blur and it is usually quite obvious that it is faked in software and is not achieved by the lens.

Someone on IRC linked me to a major manufacturer's product page (I forget which) where they were promoting their shallow depth of field phone camera, and gave loads of example pictures. Some were actually quite good, but I'd say on half of them, it was blindingly obvious that it was faked.

[magic]

What's the deal with these camera-phones, period?

They are completely rubbish (with rare exception of somebody bypassing the vendor software pipe and developing raws, if even possible on given model). They look worse than late 2000s era point and shoots with similarly sized sensors, despite a whole decade of sensor progress.

The answer is simple:
1. It's sold to proles who have never seen the real thing, so it doesn't need to look real.
2. The proles justify buying new phones every two years by thinking about all the things the phone replaces. Ergo, there is a strong marketing reason to make the proles believe that it replaces a camera too.
3. (By the same token, proles are lead to think it replaces a computer, but I'm digressing now )

Mobile phones are peak consumer technology.

[Mechatrommer]

You know china style want to imitate real bokeh of dslr with expensive telephoto lens? through AI recognition. This is it. Its been going on for years even on brand like samsung and iphone, what took you so long? There are many more! Immitate 3d view, engorge eye like grasshopper and shrink lips like shit... what do you know? The ultimatum to this AI madness is deepfake or should i call... deepshit... but to be frank its kind of cool when you on vacation you dont want to bring big heavy dslr to spoil the mood, so you still can get coolish wannabe pics even though faked and visibly imperfect to pro eyes..

[sleemanj]

Wouldn't it just be for privacy?

Now that video call meetings and so forth are common, blurring the background to prevent unintentionally showing things you don't want to show.

[Berni]

Most people take all there photos on there phone, then also do all the photo editing on the same phone before using the same phone to post it on social media.

Some of this AI image enhancement tech can be very impressive when it works. It just doesn't tend to consistently give a good result in every situation.

Phone cameras have certainly gotten impressively good too. Sure you can't compare it to a big DSLR that costs 5 times as much as the entire phone that happens to have a camera built in. It is also much bigger and heavier than a phone, making it unreasonable to carry with you unless you know you want to take a photo there. Yet photos taken by modern phones look plenty good enough to get the job done. They don't look fuzzy or dull or noisy.

[dave j]

Wouldn't it just be for privacy?

Now that video call meetings and so forth are common, blurring the background to prevent unintentionally showing things you don't want to show.

Taking photos of someone/thing with the background blurred focuses the viewers attention on the subject. It's very common in portrait photography for that reason. It's usually for aesthetic reasons rather than anything else.

[M0HZH]

What's the deal with these camera-phones, period?

They are completely rubbish (with rare exception of somebody bypassing the vendor software pipe and developing raws, if even possible on given model). They look worse than late 2000s era point and shoots with similarly sized sensors, despite a whole decade of sensor progress.

The answer is simple:
1. It's sold to proles who have never seen the real thing, so it doesn't need to look real.
2. The proles justify buying new phones every two years by thinking about all the things the phone replaces. Ergo, there is a strong marketing reason to make the proles believe that it replaces a camera too.
3. (By the same token, proles are lead to think it replaces a computer, but I'm digressing now )

Mobile phones are peak consumer technology.

Are you sure you've seen how well a decent phone camera from the last decade works?

They are "good enough" for most practical needs like taking a picture to show someone something, to post on social media or for city break snaps. People use high end mobile phone cameras even for some entry-level professional work now, with good lighting they're not that bad and they output RAW files.

I stopped taking my digital camera to most things, it only comes out for product photography or exotic holidays now. And it's a decent Sony APS-C with proper lens, certainly better than the phone camera; but it's better in areas where it doesn't really make a difference anymore.

[magic]

Yeah, sure. Go here and tell me that this is how clouds are supposed to look like. Taken in daylight with a fairly recent TOTL phone from a supposedly cloud-savvy company

This is the price you pay for

They don't look fuzzy or dull or noisy.

and noisy in particular.

[sokoloff]

What's the deal with these camera-phones, period?

They are completely rubbish (with rare exception of somebody bypassing the vendor software pipe and developing raws, if even possible on given model). They look worse than late 2000s era point and shoots with similarly sized sensors, despite a whole decade of sensor progress.

The answer is simple:
1. It's sold to proles who have never seen the real thing, so it doesn't need to look real.
2. The proles justify buying new phones every two years by thinking about all the things the phone replaces. Ergo, there is a strong marketing reason to make the proles believe that it replaces a camera too.
3. (By the same token, proles are lead to think it replaces a computer, but I'm digressing now )

I think the answer is quite a bit simpler than that: the camera that you have on you takes vastly more pictures than the camera that you don't have on you.

I have a higher quality dSLR than the camera on my phone. Yet 98+% of my pictures are taken on the camera on my phone. And it's almost always perfectly sufficient.

[Berni]

Yeah, sure. Go here and tell me that this is how clouds are supposed to look like. Taken in daylight with a fairly recent TOTL phone from a supposedly cloud-savvy company

This is the price you pay for

They don't look fuzzy or dull or noisy.

and noisy in particular.

Then just don't use your phone for taking photos if it doesn't work out for you. Nobody is preventing you from using a DSLR instead.

I got a Samsung A52s so it is far from being a flagship phone where the best phone camera tech is. But the camera is more than good enough for whatever i need to do. You can turn off the image enhancement stuff, it has a "pro" mode that gives you manual control over all the usual parameters. Pictures don't look noisy and there is plenty of detail in them. So much detail that i used it as a microscope to read tiny markings off chips (even while having the entire board in shot) or even used it as binoculars to see something that was too far for me to discern. Id don't think i could buy a brand new standalone camera that undoubtedly outperforms it for the ~300€ i shelled out for the phone brand new. And yet the camera can't make phone calls.

Maybe i am just a blind photography slob who can't tell apart a crappy potato photo apart from a good one. In any case i am satisfied with the photos my reasonably modern phone can make so i keep using it. Even if i did have a nice 3 grand DSLR i wouldn't have it with me all the time, and so a crappy photo is still better than no photo.

[golden_labels]

What's the deal with these camera-phones which attempt to fake a shallow depth of field? I'm seeing a lot of photos on the internet where there is fake background blur and it is usually quite obvious that it is faked in software and is not achieved by the lens.

The same as with people making “black-and-white” photos and various automatic, smart improvements to photos. Making photos more attractive and resembling those made by professional/artist photographers, without making any effort or having the gear.

What's the deal with these camera-phones, period?

Should I assume that to take photos of people in low-light conditions on a party you take a DSLR, “because larger more better”?

No, this doesn’t work that way. Unless we are talking about bottom tier, which is poor because it is bottom tier, each kind of gear has its specific characteristics. Some are useful in different situations, some are having detrimental effect. As it happens, any decent smartphone camera is much better for the aforementioned scenario than anything that is not a recent flagship DSLR. Aside from the latter being cumbersome for its size and energy consumption, smartphone’s smaller lens are a serious advantage. They provide longer depth of field at the same f-number. That is poor choice for some artistic uses, in particular portrait; but a massive advantage, if you take a quick photo of people from a short distance and there is no chance to keep them properly contained in DoF. Much quicker focusing is another gain.

And that’s only the technical side of the problem. Cost per quality is another one. Getting decent lens with AF and stabilization below the price of a smartphone is not that easy. No, Yangnuo is not meeting the criteria.

[coppice]

With phone cameras the selfie is king. What is the perfect selfie? One that focusses on the subject, and leaves just enough of the background discernible so the viewer can tell the subject was somewhere interesting. A controllably fuzzy background is perfect. Just add a mode that puts lipstick on a pig for the subject themselves, and you have a winner.

[magic]

Not sure why everybody is telling me to use a DSLR when I'm comparing phones to 15 year old point and shoots with similar sensor size and resolution

This has nothing to do with optics, which are approximately equal in this case, and everything to do with software processing.

Maybe there are some exceptions and I'm sure it can be bypassed by shooting raw. But phone images really aren't that great and there is at least one major phone vendor whose images are simply disgusting out of the box, see my link and just look at any part of the sky there.

[Someone]

This has nothing to do with optics, which are approximately equal in this case, and everything to do with software processing.

Really? I don't recall any "point and shoot" cameras with lenses as small in diameter and packaged in short depths like contemporary smartphones (consider Galaxy S4 zoom).

[Mechatrommer]

Not sure why everybody is telling me to use a DSLR when I'm comparing phones to 15 year old point and shoots with similar sensor size and resolution

whats your point? noise reduction? afaik noise reduction tech started to take place about 5-10 years back, 15yrs old camera you will see the green and magenta noise. today, even top notch full frame sensor will implement noise reduction just so you can snap at ISO 800K, virtually you dont need any artificial lighting in normally lit room. and nobody with selfie in mind will give a rat arse about how the sky looks, they will be more happier if noise reduction can flatten out their pimples. and RAW is nothing else than what the sensor captured. you'll need to apply noise reduction in PC anyway to deal with the ugly truth of what a small sensor can give you in RAW. you apply noise reduction, you'll get flat sky, thats what the current tech can give you, like it or not. you dont apply noise reduction, then you'll get the classic green and magenta noise, or even worse.

[Someone]

and RAW is nothing else than what the sensor captured.

Yeah, no. There is a lot of processing ahead of "raw" in the camera including noise reduction (varies by brand and model) but it tends to be a light touch leaving decisions for the human in post.

[Mechatrommer]

So thats not raw in its true meaning.. thats a 'cheated' or 'doctored' raw.. i guess manufacturer doesnt want you to know the ugly truth..

[wilfred]

Depth of field is determined by the inverse of the focal length squared, the distance to the subject (the plane of sharp focus) the aperture of the lens and an arbitrarily agreed upon circle-of-confusion or spot on the image that is not in focus but is not so blurry that it does not appear sharp in the final image ie sharp enough to be called sharp.

With tiny image sensors and very short focal length lenses and no (or very limited) ability to vary the aperture, everything that makes a camera phone so convenient works against producing images with pleasing background and foreground blur that can produce the desired effect in the final image. Cameras with much larger sensors and in particular full-frame sensors have the physics of the optics available to exploit in a way camera-phones do not.

Clever software image processing is used to overcome the inherent limitations of cameras built into phones.

Even back in the day lenses were often characterised as having pleasing "Bokeh" in the out-of-focus areas and lenses with more nearly circular aperture diaphrams tended to excel in this regard. Six bladed diaphrams would make blurred highlights appear as hexagons.

So there is very little possibility for a camera-phone to produce real background blur.

[Berni]

Maybe i just struck it lucky with my particular phone that i never ran into processing artifacts. Then again the camera on this phone did jump onto the megapixel pissing contest bandwagon with a 64MP sensor, so it gives any noise reduction post processing more pixels to work with. That's likely the only use for the ridiculous megapixel numbers since the optics probably can't make proper use of it.

One way you can really make the post processing show up is to use the night shot mode and take a photo at night. It can actually produce a impressively bright looking photo even in very dark scenes. However any fine detail is completely smeared out into solid colored blotches, it really does look ugly. However the original pixel data from the camera sensor was likely way way worse, probably mostly static with a faint representation of the actual scene behind it. So while the post processed night shot image does look ugly they are still a lot better than the unusable noisy garbage the sensor actually produced.

But in normal lightning conditions the decent modern phones produce perfectly fine images to me. All i see is JPEG compression artifacts if i zoom way in(Even that takes a lot of zooming in on a 10MB jpeg).

[Mechatrommer]

They look worse than late 2000s era point and shoots with similarly sized sensors, despite a whole decade of sensor progress.

Then again the camera on this phone did jump onto the megapixel pissing contest bandwagon with a 64MP sensor, so it gives any noise reduction post processing more pixels to work with. That's likely the only use for the ridiculous megapixel numbers since the optics probably can't make proper use of it.

this.. even though similar sensor size.. P&S cameras 15 years back have only like 2-4MP, todays sensor is 24-64MP size. so per pixel size is really small on modern sensor hence more noise. we dont expect too much from noise reduction technology yet... so give and take.

[AndyBeez]

@Steve30 - one of my pet peeves! It's not a light gaussian glur but a total distracting fuzz. It could be justified as a bandwidth saver by removing complex backgrounds from the algorithm? But no, it's there on F2F calls so people don't show what a shite collection of ornaments and books they have on the shelf behind them. Personally, I've only ever seen gaussian blur used to good effect on tilt-shift imaging. Okay, not quite as irritating as the teeth whitening mode on Samsung phones, but agreed, a CRAP FX.

You'll note this selective depth of focus effect creeping into news reports. Back in my day as a camera operator, focus had to be this >|< sharp. Always. And if the subject moved, the opo' had to pull the focus - hence the Focus Puller on movie credits. Now, it's used to 'drift attention' to the action, often by the news reporter who went to a five minute film school on Youtube. Again, a CRAP FX.

[steve30]

You'll note this selective depth of focus effect creeping into news reports. Back in my day as a camera operator, focus had to be this >|< sharp. Always. And if the subject moved, the opo' had to pull the focus - hence the Focus Puller on movie credits. Now, it's used to 'drift attention' to the action, often by the news reporter who went to a five minute film school on Youtube. Again, a CRAP FX.

I do some video journalism as a hobby these days and I find smaller sensor cameras best as just about everything is always in focus. I find with interviews, it can be quite pleasing to have a smidgen of background blur, which can be achieved by moving the camera further back and zooming in; this can help emphasise the person who is talking, but usually the background is important, as there is often something happening there which is relevant.

Larger sensor cameras are much better in low light; in fact the 0.4" camera which I recently spent over £1000 on is rather crap in low light. So I can see the appeal of larger sensors. I also notice amongst hobbyists, that quite a few people use DSLRs. I consider these not very good for anything which might be considered "news", but for hobbyists/low budget business it may be the best option, especially if you do a lot of still photos, or need the low light sensitivity. But even if a DSLR news report has excessive background blur, at least it is proper lens blurring and not that faked stuff!

The issue with the fake DOF is that the camera often doesn't know the actual distances involved, so in a portrait, the face will be in focus, but the ears will be blurred, and will be blurred by the same amount as the wall behind them.

There was one good example on a manufacturers website where the person was stood on a bridge. The railings (which were probably a few meters away from the camera) were blurred, but the background in between the railings was pin sharp, but the [same] background above the railings was blurred!

[TimFox]

Another way of looking at depth of field is that it depends directly on the "film" or "sensor" size.
A "full-frame" DSLR sensor is 24 by 36 mm, just like a frame in a 35 mm film SLR, and will have a shallower depth of field than, say, 4.2 by 5.6 mm (IPhone 14) at a given f-number.
The exposure depends on that f number, the exposure time, and the actual speed (ASA/ISO) of the film or sensor.
When I started using an 8 x 10 inch camera to photograph flowers, I immediately noticed the shallow depth of field at a given f-number.
(The actual image quality, when the damn flowers quit blowing in the breeze, blows any cell phone out of the water.
I was photographing buildings down by the Chicago River when a tourist asked me how many megapixels I had with the 8x10.
I did a quick back-of-the envelope mental calculation, and replied, honestly, "about 500".)

[Mechatrommer]

photo/video graphy is 10% tools and 90% technique (art). technique including manipulating lights and reflectors and art about subject matter and background story telling, framing and know what/where/why to emphasize or de-emphasize. all-sharp picture is property of pin-hole camera you can even diy, but real bokeh/blur (to de-emphasize) need some price. you can get all-sharp with dslr and kit cheap (slow) lens, set to highest f-stop (smallest aperture) that the light level can allow and shot away your video, but its quite tricky (or limited condition) if not impossible to get bokeh with pin-hole grade camera like phone camera. current artificial blurring of smartphone is not yet near perfection and as good as real deal big camera and "fast" lens... today dslr only if you want to make some money, if you want to make money with smartphone camera forget it, everybody have it now they can make their own, unless you have the special 90% of technique and art mastery or youtube paybill creating fool in foreground commenting game in the background with $5 ring led as artificial light..

[AndyBeez]

Fake DOF just looks wrong. This and other clunky effects might be on trend, but there is no excuse for them being on air. As you say, step back and zoom in makes not only for a more natural DOF feel but also, it flattens the perspective on the subject. A short telephoto lens always makes for a good portrait. Smart phones do zoom by cropping away a few mega pixels - the perspective and focus stuff is done by silicon guesswork.

[brucehoult]

The issue with the fake DOF is that the camera often doesn't know the actual distances involved, so in a portrait, the face will be in focus, but the ears will be blurred, and will be blurred by the same amount as the wall behind them.

There was one good example on a manufacturers website where the person was stood on a bridge. The railings (which were probably a few meters away from the camera) were blurred, but the background in between the railings was pin sharp, but the [same] background above the railings was blurred!

The actual TOTL recent phones use multiple lenses with a (small!) displacement between them, which is presumably enough to get some depth information.

iPhone 12, 13, 14 also have LiDAR to directly get depth information in different parts of the image. Samsung's Galaxy S10 and S20 also have LiDAR, but apparently it's a cheaper implementation that doesn't work as well as Apple's and they're dropping it in newer models.

[Someone]

The issue with the fake DOF is that the camera often doesn't know the actual distances involved, so in a portrait, the face will be in focus, but the ears will be blurred, and will be blurred by the same amount as the wall behind them.

There was one good example on a manufacturers website where the person was stood on a bridge. The railings (which were probably a few meters away from the camera) were blurred, but the background in between the railings was pin sharp, but the [same] background above the railings was blurred!

The actual TOTL recent phones use multiple lenses with a (small!) displacement between them, which is presumably enough to get some depth information.

The other trick being that n cameras capturing the same scene from different positions can be combined to produce something approaching a lens of the same area, incoherent synthetic aperture. Add a couple of complementary methods on top of each other and the synthetic bokeh can be good enough for the unwashed masses.

[Mechatrommer]

i was the owner of Samsung KZoom, that was the closest thing to real bokeh and telephoto at smallest and lightest phone form factor that fits in a pocket. but since i need 2 SIM slots now, which is not available in KZoom, i have to buy newer phone, but sadly no more replacement (younger version) like KZoom, i guess not much sale and not trending. so i have to buy 3-pin-holes smartphone now. and then i found SONY DSC-QX10 (WHITE), wifi attachable to pin-hole smartphone. if i want real zoom and light for personal use (digital zoom is another older toy in existance in hunglow P&S camera and smartphone) thats the one i will grab. but sadly the DSC-QX10 type also extinct.

[magic]

Depth of field is determined by the inverse of the focal length squared, the distance to the subject (the plane of sharp focus) the aperture of the lens and an arbitrarily agreed upon circle-of-confusion or spot on the image that is not in focus but is not so blurry that it does not appear sharp in the final image ie sharp enough to be called sharp.

Another way of looking at depth of field is that it depends directly on the "film" or "sensor" size.
A "full-frame" DSLR sensor is 24 by 36 mm, just like a frame in a 35 mm film SLR, and will have a shallower depth of field than, say, 4.2 by 5.6 mm (IPhone 14) at a given f-number.
The exposure depends on that f number, the exposure time, and the actual speed (ASA/ISO) of the film or sensor.
When I started using an 8 x 10 inch camera to photograph flowers, I immediately noticed the shallow depth of field at a given f-number.

Another? This is the absolutely common way of looking at DoF which has already been posted by the guy above. It can be found on Wikipedia, and that's definite proof that it is misleading, inaccurate and of limited practical utility in ways that they never disclose.


I will show how to derive DoF from first principles.

Let θ be the maximum acceptable angular blur, or the demanded angular resolution or something like that. Let's say it's a small angle in units of radians so I can pretend that tgθ=θ. If U is the object distance then define C_o as the object-referred circle of confusion, i.e. C_o = U·θ.

By simple application of similar triangles, C_o/(½DoF) = D/U, where D is the entrance pupil diameter of the lens. See here.

Therefore,
2·C_o = D/U·DoF
DoF = 2·C_o·U/D
DoF = 2·U²·θ/D


For more practical convenience, you could replace θ with something derived from angle of view and expected resolution in lines per picture size. I didn't bother, to keep the calculations shorter.

Observe that neither focal length, nor sensor size, nor image-referred circle of confusion make any appearance in this formula. DoF is an object space phenomenon and what happens in the image space is simply not relevant. The only part of the camera which matters is the entrance pupil, and the only limitation is whether you can find a lens with given entrance pupil diameter for whatever image circle and angle of view you may want.

In practice, wide angle lenses for small sensors have short focal length, which puts an upper bound on D by the virtue of practical limitations on how small f/D ratios can be realized. Hence shallow DoF is not achievable on small sensor cameras, but large DoF can be achieved on large sensors because large f/D is not hard. Just stop down.


But if you must introduce the f-number, perhaps because your lens vendor didn't print the pupil diameter on the lens, it's trivial to plug it into the formula in place of D.
DoF = 2·U²·θ·N/f

And now a big lie, because the widely known formula simply doesn't work macro. But let's pretend that image distance behind the lens is just the focal length f. Then f/U is the magnification and the image-referred circle of confusion C_i becomes C_i = C_o·f/U = θ·f.

Then we get the familiar, difficult to understand, and subtly wrong version from Wikipedia. QED.
DoF = 2·U²·N·C_i/f²

[TimFox]

There are different equivalent equations for depth of field.
A problem I always had is determining the appropriate circle of confusion for a given application, since that needs to go into any calculation.
Past that, when comparing two different cameras, the variables known to the user are
--f-number, which also determines the exposure when combined with the exposure time, i.e. "reciprocity".
--Frame size:  the size of the image on the film or sensor.
--Distance from lens plane (technically, entrance principal plane to subject)
--Field size:  the total angle mapped onto the frame, which determines the required focal length for a given frame size.

My comment was based on my evolution with film photography:  starting with 35 mm, then 4x5 inch, and finally 8x10 inch, with some 6x9 cm along the way.
I quickly noticed, judging DOF visually, that I had to decrease the aperture (increase the f-number) for a given visual DOF with increasing frame size, requiring longer exposures.

Yes, macro focusing is different, since the equations for the above simplify when the lens-frame distance is close to the focal length (focused at infinity), while at 1:1 magnification, the object distance and film distance both equal twice the focal length.

[magic]

My comment was based on my evolution with film photography:  starting with 35 mm, then 4x5 inch, and finally 8x10 inch, with some 6x9 cm along the way.
I quickly noticed, judging DOF visually, that I had to decrease the aperture (increase the f-number) for a given visual DOF with increasing frame size, requiring longer exposures.

That's what everybody notices, except it's different digital sensor sizes with kids these days


The point of my rant is that there actually exists a simple (and easy to calculate) parameter of the lens, which pleasantly stays constant when you try to produce similar images with different formats. And that there are simple geometric reasons why it is so.

The same principle also applies to things like exposure, sensitivity and noise. ISO100 on a phone is a completely different thing than ISO100 on 35mm frame. And it frankly should be called something else than ISO100. People try to patch the traditional theory with concepts like "35mm equivalence", but IMO it's still a convoluted way of thinking, full of traps (when to apply crop factor scaling or not) and it surely doesn't help that "equivalence" is often applied selectively by manufacturers to a subset of specs which make their product look favorable compared to alternatives from other formats, but not to some other specs.

I find that for comparison of different formats it is usually possible to completely eliminate the format and parameters which are tied to it (the focal length / angle of view relationship, f-number, ISO speed) and replace them with objective quantities referring to the object, available light and the final output image. The above DoF formula was an example of such approach.

This doesn't seem to be nearly as obvious and well known as it should be. Many people still walk around:
a) using cookbook formulas without understanding
b) not knowing stupid limitations of their applicability (like that thing above about macro)
c) thinking that they need a small camera for more DoF
d) advising others to switch to a smaller camera for more DoF


There also seems to be little interest in promoting honest comparisons by manufacturers. I'm shocked.


BTW, it seems I still failed to account for the change of C_o with distance.
As written, my formula doesn't predict the possibility of hyperfocal focusing.

[TimFox]

"35 mm equivalence" is a buzzword for relating the focal length in a camera with a different frame size, commonly used for "crop-factor" sensors such as the popular "APS-C" frame that is roughly 2/3 the linear size of a "full-frame".

ASA/ISO "speeds" originated with photographic film, and essentially measure how much light does it take per unit area at the film to expose that area.
Ignoring depth of field for a moment, in normal (non-macro) operation, the exposure is a function of only the ASA number, f-number, and exposure ("shutter") time.

Technically (nobody follows this, however), with film, since the chemical development directly affects the slope of the exposure curve, the ASA number related to the "toe", where exposure rises from the background density.
"EI", "exposure index", measured in the same units, is useful for E-6 films (with standard development), and corresponds to the "middle" of the curve from zero to full exposure.
With film, you can manufacture it in very large sheets and cut it down to the desired size, and the ASA number remains constant.
The same measurement works for solid-state sensors, with reference to unit area in the sensor plane.

[magic]

"35mm equivalence" is used for more than focal length. People talk about "equivalent aperture", which means same DoF and light gathering power as some reference lens, angle-of-view-equivalent on 35mm frame. They may or may not realize that it simply means equal pupil diameter. There is apparently a concept of "equivalent ISO", which means similar noise level and same brightness if the other "equivalences" are met. It's a wholly developed theory.
https://photographylife.com/equivalence-also-includes-aperture-and-iso

Regarding commercial examples, I recall some Sony/Zeiss fixed lens camera being marketed in terms of 35mm equivalent focal length and aperture; these numbers were actually printed on the lens in place of real ones. I don't like it very much, but I understand the marketing value and appreciate the honesty, compared with phone manufacturers advertising equivalent focal length but true f-stop.

Olympus came up with "magnification equivalence" for their 4/3 SLR macro lenses.


Most of that Theory Of Equivalence wouldn't be necessary if different metrics were used in the first place.
1. Replace f-stops with pupil diameter. This gives DoF and light-gathering equality between formats.
2. Replace exposure value with total collected light: D²·FOV²·t. This gives important shot noise equality between formats and is consistent with 1.
3. Replace ISO with sensitivity per whole frame rather than per unit area, for consistency with 1&2.

In my world, smartphones would start at ISO-four-digits and have the level of noise expected from that. Lenses would need to be marked with angle of view for convenience. Not a big deal, they are married to a particular system anyway. Only users who adapt lenses on different formats would need to worry about crop factors (appearing in the FOV² part). Now, everybody needs to worry about crop factors when selecting format to meet particular DoF or SNR target. Or ignore it and almost surely end up misled by marketroids.

This system also seems to work better for macro, without needing kludges like "effective aperture". The tricky part now becomes knowing FOV, because it varies despite constant focal length. Arguably, FOV variation with magnification is something that already exists anyway and one must be aware of, no matter what approach is used to calculate exposure.


It's all pure madness, I know

[TimFox]

In my photographic usage, the most important thing is exposure.
For large format, I use a spot meter.
DOF matters, but not so important.
When switching lenses (and possibly films), the relevant parameters are f-number and conventionally-defined ASA.
I will get the same exposure from a given subject highlight at 1/125 sec and f/8 with a 50 mm lens or 135 mm lens, up to my 600 mm lens that covers 8x10.
Similarly, I will get the same exposure from a highlight for 35 mm or 8x10 inch ASA 100 film with those shutter times and aperture expressed as f-number.

For metering macro, I take the lens-to-film distance and use it in an inverse-square calculation (compared to the focal length) and set the ASA dial on my spot meter accordingly.

[Mechatrommer]

those EV meter + ASA/ISO chart are long gone imho, its now built-in and automatic. even if we have to be manual, all it takes now is 1 or few quick shots in a second and look at the built in histogram. thats why more and more people are not aware of them, even on the still currently used focal-length/f-number/shutter speed/iso combo in real pro dslr mode...

[TimFox]

Where's the sport in that?
Have you ever indulged in focusing a complicated subject on a ground glass with the help of a loupe, or is it all done for you?

On my office wall before I retired, I mounted a 16x20 inch Ilfochrome print made from a 4x5 transparency (Kodak 64T) that was carefully focused and exposed.
A side view of the workings of a steam locomotive in a railway museum, lit with tungsten lights.
I had a challenge to the junior employees to make a print with equal technical quality (artistic quality is in the eye of the beholder), spending less than ten times as much as the equipment I used to make the image.
No replies.

[Someone]

ASA/ISO "speeds" originated with photographic film, and essentially measure how much light does it take per unit area at the film to expose that area.
Ignoring depth of field for a moment, in normal (non-macro) operation, the exposure is a function of only the ASA number, f-number, and exposure ("shutter") time.

Technically (nobody follows this, however), with film, since the chemical development directly affects the slope of the exposure curve, the ASA number related to the "toe", where exposure rises from the background density.
"EI", "exposure index", measured in the same units, is useful for E-6 films (with standard development), and corresponds to the "middle" of the curve from zero to full exposure.
With film, you can manufacture it in very large sheets and cut it down to the desired size, and the ASA number remains constant.
The same measurement works for solid-state sensors, with reference to unit area in the sensor plane.

That last bit is where it all falls apart, exposure is relative to the resulting "intensity". For digital cameras there are a variety of ways to rate ISO (which the camera manufacturers usually dont advertise) but its not per unit area or per pixel if going by the intensity measure. Below is the PTC/noise plot for a canon R3 from public data (Review at www.the-digital-picture.com) across ISO levels, that camera has a linear response in the sensor with enough dynamic range they can use the level based Standard Output Sensitivity or Saturation method to rate the ISO speeds (and then round them to convenient steps). ISO just becomes gain in that situation (with it approaching shot noise limited for modern sensors).

Thus your traditional exposure calculations still work to maintain your expected 18% exposure point. Compared to film the noise characteristics are different and there is no knee in the exposure, but you can add that back in post with a high bit depth or raw workflow.

Dynamic range and noise based ISO ratings are dependent on the pixel size/area etc, and that is where some manufacturers cheat with "equivalents". But it is easy enough to find or make proper assessments of any specific camera and get around those marketing lies.

[magic]

On my office wall before I retired, I mounted a 16x20 inch Ilfochrome print made from a 4x5 transparency (Kodak 64T) that was carefully focused and exposed.
A side view of the workings of a steam locomotive in a railway museum, lit with tungsten lights.
I had a challenge to the junior employees to make a print with equal technical quality (artistic quality is in the eye of the beholder), spending less than ten times as much as the equipment I used to make the image.

You chose a static subject (I think?) so I imagine something could be attempted with a tripod and panorama tricks. Other than that, no clue.

I will get the same exposure from a given subject highlight at 1/125 sec and f/8 with a 50 mm lens or 135 mm lens, up to my 600 mm lens that covers 8x10.
Similarly, I will get the same exposure from a highlight for 35 mm or 8x10 inch ASA 100 film with those shutter times and aperture expressed as f-number.

Yeah, I can see how this can be convenient, particularly if calculations are done by hand. My suggestion of "obviously, changing to narrower FOV means you increase the pupil by the same ratio to compensate" may not be equally compelling, even if this is exactly what happens when you go from 50/8 to 600/8.

The purpose of 35mm equivalence and my format-agnostic framework is navigating the crazy world of digital, where exposure is a solved problem (easily and quickly done empirically even when you don't trust AE) and the greatest challenge facing humanity is penny pinching by getting away with the smallest and cheapest sensor you can buy. Or sell to somebody Either way, the result is that things now need to work closer to physical limits than in the past.

[steve30]

"35 mm equivalence" is a buzzword for relating the focal length in a camera with a different frame size, commonly used for "crop-factor" sensors such as the popular "APS-C" frame that is roughly 2/3 the linear size of a "full-frame".

My new video camera advertises itself as being "25mm Wide". Of course it is actually a 4.12mm lens.

[TimFox]

On my office wall before I retired, I mounted a 16x20 inch Ilfochrome print made from a 4x5 transparency (Kodak 64T) that was carefully focused and exposed.
A side view of the workings of a steam locomotive in a railway museum, lit with tungsten lights.
I had a challenge to the junior employees to make a print with equal technical quality (artistic quality is in the eye of the beholder), spending less than ten times as much as the equipment I used to make the image.

You chose a static subject (I think?) so I imagine something could be attempted with a tripod and panorama tricks. Other than that, no clue.

I will get the same exposure from a given subject highlight at 1/125 sec and f/8 with a 50 mm lens or 135 mm lens, up to my 600 mm lens that covers 8x10.
Similarly, I will get the same exposure from a highlight for 35 mm or 8x10 inch ASA 100 film with those shutter times and aperture expressed as f-number.

Yeah, I can see how this can be convenient, particularly if calculations are done by hand. My suggestion of "obviously, changing to narrower FOV means you increase the pupil by the same ratio to compensate" may not be equally compelling, even if this is exactly what happens when you go from 50/8 to 600/8.

The purpose of 35mm equivalence and my format-agnostic framework is navigating the crazy world of digital, where exposure is a solved problem (easily and quickly done empirically even when you don't trust AE) and the greatest challenge facing humanity is penny pinching by getting away with the smallest and cheapest sensor you can buy. Or sell to somebody Either way, the result is that things now need to work closer to physical limits than in the past.

The locomotive was stationary (for many years), and I used a simple 4x5 field camera, 135 mm/5.6 Nikkor-W, and a tripod.
I maybe spend $1200 total for that setup (in a previous century).
Again, I concentrate on exposure for my purposes, and my large-format work always requires long exposures. 
Keeping the highlight exposure constant is a reason why good zoom lenses (for DSLR and SLR cameras) have a constant f-number when zooming.
That is a non-trivial design lens design problem.
I am a curmudgeon, and remember the second half of the 20th Century, where technical progress resulted in better results (audio reproduction fidelity, photographic speed and resolution, etc.).
In the 21st Century, "best possible" has been replaced by "good enough", or as you put it, "penny pinching by getting away with...".

[TimFox]

"35 mm equivalence" is a buzzword for relating the focal length in a camera with a different frame size, commonly used for "crop-factor" sensors such as the popular "APS-C" frame that is roughly 2/3 the linear size of a "full-frame".

My new video camera advertises itself as being "25mm Wide". Of course it is actually a 4.12mm lens.

Another parameter to beware is when sensor size is quoted as, essentially, vidicon equivalent size.
When I was looking for the physical sensor size for the IPhone14, which is 4.2 by 5.6 mm active area, I found it specified as 1/1.28".
Literally, (1 inch)/(1.28) = 19.8 mm, which is much larger than the actual size:   the diagonal of a 4.2 by 5.6 rectangle is only 7 mm.
I had run into that specification before when looking at industrial sensors, and it has something to do with the outside (glass) diameter of an equivalent vidicon.
A 1" sensor is actually 8 by 13.2 mm.

[Mechatrommer]

Where's the sport in that?

The locomotive was stationary (for many years), and I used a simple 4x5 field camera, 135 mm/5.6 Nikkor-W, and a tripod.

sport photography dont have time to setup all that... still photography is only a fraction of photography discipline/business/hobby, which i dont do much the closest i do is landscape both during the day and night... where is the sport? doing much lightroom work (previously known as darkroom processes), HDR, color correction/enhancement, photos stitching etc... heck even HDR and stitching process are now AI'ed in smartphone. you know? fondling those dark area in your locomotive so in the end printouts just look like the way we see the locomotive with our own eyes... making it surreal while maintaining naturality, is another art... ymmv.

[TimFox]

Where's the sport in that?

The locomotive was stationary (for many years), and I used a simple 4x5 field camera, 135 mm/5.6 Nikkor-W, and a tripod.

sport photography dont have time to setup all that... still photography is only a fraction of photography discipline/business/hobby, which i dont do much the closest i do is landscape both during the day and night... where is the sport? doing much lightroom work (previously known as darkroom processes), HDR, color correction/enhancement, photos stitching etc... heck even HDR and stitching process are now AI'ed in smartphone. you know? fondling those dark area in your locomotive so in the end printouts just look like the way we see the locomotive with our own eyes... making it surreal while maintaining naturality, is another art... ymmv.

"Where's the sport in that?" is a joke, not a reference to sports photography.
Some of the greatest sports photos from the middle of the last century were done with 4x5 inch Speed Graphics.

[Mechatrommer]

"Where's the sport in that?" is a joke, not a reference to sports photography.

clearly you didnt read until the end i think btw i didnt have the chance to play with film back then because it was "not my age", except my first learning in 2nd school my uncle lent me his Olympus SLR, cant afford real full darkroom back then. let alone the chance to play with large/medium format size, even today descendant of large/medium format (digital) is very much unaffordable, so i have to do whatever it takes in small format 35mm, currently known as full frame sensor... but then, nothing we cant do in cropped format APS-C DSLR except a little bit of noisier picture in low level lighting.

[magic]

35mm is small format, medium format digital is expensive, and large format digital doesn't seem to be much of a thing.

You would pay for having half of a silicon wafer processed just for yourself.
If you are lucky and it works out, because defect probability increases proportionally to chip area...

[magic]

but then, nothing we cant do in cropped format APS-C DSLR except a little bit of noisier picture in low level lighting.

Noise is a fundamental problem for webcams and cellphones, astrophotographers and action shooters. If you have noise in other situations, you are probably doing it wrong and tripod and/or lighting is the best bang for he buck solution.

Resolution is where small formats will always lose to larger ones and mosaic/panorama stitching is the only trick that can get you out of this, provided that your subject/scene is perfectly still. If you try to fish out the same details out of a smaller image, you inevitably reach a point where you run into diffraction. Then you need a "faster" lens to push it away, and you inevitably reach a point when you run into optical aberrations. Then you're done for good.

And we come full circle back to the original topic, because overdone sharpening is another reason why phone images suck. They just can't resist the temptation

[AndyBeez]

The unsharp mask can never replace resolution lost from lossy compression. Even if it's turned up to 11. All you get is obvious artefacts.

On the subject of noise, some year's ago I tried cooling a MOS detector with a Peltier cooler for astro photography use. The noise floor certainly lowered, but frosting on the sensor made the imager somewhat useless after five minutes - exposures were for 10+ minutes. Today, a contemporary DSLR back and stacking images, will do in your backyard what was done on a mountaintop observatory in sheet film some 40 year's ago. Electronics needs electrons to get excited, but not too excited.

[steve30]

These two came up on my Flickr homepage today. I'd say they are pretty representative of the fake blurring problems we are seeing regularly at the moment.

https://flickr.com/photos/emoisland/52541085884/in/dateposted/
https://flickr.com/photos/emoisland/52540786156/in/dateposted/

On the first one, the actual blurred background looks OK, but you can clearly see where the blur has spilled over onto the person, and where it has not gone in quite far enough, thus creating a noticeable outline. It has also got the depth of field completely wrong with one of the legs.

On the second photo, it got the depth of field right for the leg, but not the wooden floor he is standing on. In fact, it looks like he has been cut out of another photo, and pasted on the background.

Both photos suffer excessive sharpening on the 'in focus' parts. Flickr says they are done on an iPhone XR at ISO 400 4.2mm f/1.8.

[AndyBeez]

Those are fake blurgrounds? 

Looks like someone was new to learning layers in Photoshop. ( having seen what some so called web graphic designers achieve after three year's at uni, that might be considered proficient ).

Disclosure: I learnt my photography looking down a Lupe and stressing over film grain. If you know Kodachrome 25/64, Fuji RDP or Ilford PanF and XP2, then you'll know what I'm talking about. There is a generation for whom grain is something they add in Lightroom, to give an image the feel of a bygone era.

[TimFox]

Many years ago, film photographers would use very high speed Kodak films intended for surveillance purposes to get exaggerated grain for artistic purposes.
Before that, there was a painting style called "pointillism".
A famous example, now at the Art Institute of Chicago, is Seurat's "Sunday on La Grande Jatte".  https://artsandculture.google.com/asset/a-sunday-on-la-grande-jatte/twGyqq52R-lYpA?hl=en&ms=%7B%22x%22%3A0.5%2C%22y%22%3A0.5%2C%22z%22%3A9.4555024148453%2C%22size%22%3A%7B%22width%22%3A1.616855466120035%2C%22height%22%3A1.2375000000000003%7D%7D
Perhaps, that is the only painting to be adapted into a musical comedy, "Sunday in the Park with George", by Sondheim et al.

[Mechatrommer]

ps: this is partly in respond to magic's confusion on current vs previous HW vs SW tech in photography... and also partly related to the OP's topic... recently Topaz AI (SWs from Topaz Labs) got into my radar, its quite amazing SW at image recovery in general, and to my current definition, its a magic bunch of softwares, implementing AI model/database into otherwise classical method of image enhancement/enlargement/noise reduction... (the most surprising to me is Topaz Gigapixel AI at recovering blurry face into sharper and enlarged size... but thats off topic) the sample picture below was taken using Canon EOS 7D Mk2 @ ISO 6400 @ lens 17mm f/2.8... before.jpg is cropped portion of image, unscaled after what i guess as the best camera's built-in algorithm at reducing image's noise out of the 20Mpx APS-C sensor.. after.jpg is further enhancement using Topaz Denoise AI... the improvement imho is significant, although there are still imperfection to the AI algortihm, we still can see sort of aliasing somewhere... if you think noise problem is only for astronomers? try shooting an event in large ballroom with dark paint on every walls without your own artificial lighting and without full frame sensor at hand, high iso and less noisy pictures can really usefull!... my point is if such AI algorithm can be implemented real time in small sensor camera such as smartphones and even smaller sensor dedicated camera such as APS-C format, better (perceived) image quality or larger Mpx size can be achieved further... but this magic AI software has GBytes of installation and model files, so i believe currently its only for powerful PC and not real time. what i would like to see is Topaz "Fake Blur Backround" AI algorithm to get better fake-blur background but then currently there is no yet can beat real optic blur, hence i'm getting a used Canon 85mm f/1.2 because of that, after many years playing with less fast f/2.8 zoom lenses...

[magic]

Meh.
Didn't know that there are stars inside oscilloscopes

[steve30]

That's actually quite a good job of denoising.

[Mechatrommer]

That's actually quite a good job of denoising.

there is no free lunch, every denoise algorithms will kill away some details as magic described last year about the "flatten" sky, older point and shoot (no-denoiser, ie alot of random color noises, but no flattened sky) vs modern smartphone/camera (with denoiser built-in, less apparent noise, esp color noise, but with flattened sky), similar to when trying to recover original data from lossy compression, its impossible. modern AI algorithm seems capable of doing it, but imho its just an illusion, a try and guess and assume method of what it was. Topaz can produce some funny faces (not me and not who the people i know) when original file is excessively noisy or blurry than what the algorithm "expects"... normal users usually wouldnt notice until they compare the picture with more expensive larger sensor dedicated camera (dslr), no noise and sharper optics. ymmv.

[magic]

It's doing good job on large flat areas, but that's an easy job. And I guess it's also doing a good job of detecting such areas.

On areas with more busy detail it seems to switch to sharpening and only makes noise worse. The grilles of the equipment look ugly.

There is some sort of paper or cloth on the lower piece and it got some texture on it which is probably just noise amplified by the processing.

The text "keyboard" changed to "kθyboard", which would be a meaningful error in "serious" applications like text recognition or machine vision.
There is a blurry and noisy red text on a book or box in the bottom right corner, turned into meaningless curved lines. "Fake it and maybe you'll make it".

Overall contrast of the image was increased too. The white metal construction is brighter, I think parts of it are blown out, even.

edit
Next time you could also produce a longer exposure shot at lower ISO for reference, to compare the "enhanced" image against reality.

[Mechatrommer]

yes agreed, AI that is not clever enough, exactly this thread is all about.. i'm not going to do in-depth comparison in ee forum, and i should've setup a better controlled environment rather than a random mess. i know what it is, it is what it is. i just took a random picture, in the way mimicking the way i usually did in low light and challenging event. or pushing or knowing the limit of high iso high noise and how good today's denoise can do.. this AI still need human AI (actual intelligent) touch to improve or select the good part of it in photoshop and mask out the worse parts.. but it will need time... ymmv.

[Berni]

Yeah right now AI is best when guided by an actual human.

The benefit of AI in image editing is automating the tedious tasks. Like an easy example is "content aware fill" to remove something from a photo. Doing that by hand can be very time consuming to grab the correct parts of the background, duplicate them out in a way that doesn't make an obvious repeating pattern, align them well, blend it in to the rest..etc. The content aware fill simplifies that down to just selecting the thing you want gone and waiting a fraction of a second. Saves a massive amount of time.

[coppice]

Yeah right now AI is best when guided by an actual human.

Yeah, right now a novice human is best when guided by a skilled human,

[5U4GB]

Someone on IRC linked me to a major manufacturer's product page (I forget which) where they were promoting their shallow depth of field phone camera, and gave loads of example pictures. Some were actually quite good, but I'd say on half of them, it was blindingly obvious that it was faked.

Well, people with DSLRs buy fancy tilt-shift lenses to get the same effect, so someone probably thought "hey, lets emulate that in software!".  There are times when it's pretty useful... OK, not many times, but still some, and given the useless junk phone vendors are now putting in they've pretty much run out of ideas elsewhere.

[TimFox]

Someone on IRC linked me to a major manufacturer's product page (I forget which) where they were promoting their shallow depth of field phone camera, and gave loads of example pictures. Some were actually quite good, but I'd say on half of them, it was blindingly obvious that it was faked.

Well, people with DSLRs buy fancy tilt-shift lenses to get the same effect, so someone probably thought "hey, lets emulate that in software!".  There are times when it's pretty useful... OK, not many times, but still some, and given the useless junk phone vendors are now putting in they've pretty much run out of ideas elsewhere.

Once the image is formed at the sensor or film surface, it cannot be re-focused.
Of course, one can apply filters to the image data in order to, for example, boost the high-frequency content of the image after that, or smoosh the high frequencies to obtain blur.
The purpose of a tilt-shift lens is to obtain a limited effect, better done with a "view camera", to establish a plane of best focus (in object space) that is focused onto the image plane, by tilting the lens plane with respect to the image plane;  view cameras have far more tilt angle and shift displacement than a normal "tilt-shift" lens for an SLR or DSLR.
"Tilt" here means rotating the lens holder about a horizontal axis, and "swing" means rotating about a vertical axis, depending on the exact application, possibly of both.
For example, a typical Ansel Adams photograph would tilt the lens down so that the top of a distant mountain and the brook close to the camera are both in good focus, allowing the less interesting object space between them to go "soft". 
"Shift" means displacing the lens axis with respect to the center of the image.
This is useful, for example, when you make the lens and image planes vertical, to avoid convergence of vertical lines in the tall building you are imaging, and shift the lens upwards to reduce the amount of parking lot in the foreground.
For a detailed analysis, look up the "Scheimpflug principle":  https://www.opticsforhire.com/blog/scheimpflug-principle/