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How-to make decent photographs for forum posts/articles/publications?

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RoGeorge:
That's nice!

In terms of minimizing the pics for web, I'm using 'convert' (from the 'imagemagic' package, often preinstalled), a command line tool for Linux, good to strip the extra info and to resize the original jpegs to half (1024px wide), then compress them a little better.

The camera is an ancient Minolta DiMAGE Z1, 3MP, better than a DSLR for close up pics.  In general, cameras with a smaller area sensor give better depth of field for closeup/macro shots than a camera with a big sensor.  DoF is bigger when the sensor is smaller (small in size, not in pixels) and this is so because of physics/math, it's not just an artistic bias.

The set of parameters that worked best for me, by turning a 1.5MB (2048x1536 px) .jpg into a 30-50kB (1024x768 px) .jpg, about 30 times smaller while the quality is preserved well enough for web posting:

--- Code: ---convert "PICT3090.JPG" -strip -matte -resize 1024 -quality 50% -sampling-factor "2x2, 1x1, 1x1" "PICT3090_s.JPG"
--- End code ---

Same pic as in the attachment, but resized + compressed 50% using Gimp has about 80k, looks slightly better but the quality difference is noticeable only when compared side by side, otherwise the smaller one prepared with 'convert' would be just as good:



For a comparison, the original is PICT3090.JPG, 1.5MB.

magic:

--- Quote from: RoGeorge on August 11, 2022, 08:55:23 am ---The camera is an ancient Minolta DiMAGE Z1, 3MP, better than a DSLR for close up pics.  In general, cameras with a smaller area sensor give better depth of field for closeup/macro shots than a camera with a big sensor.  DoF is bigger when the sensor is smaller (small in size, not in pixels) and this is so because of physics/math, it's not just an artistic bias.
--- End quote ---
Are you sure that sensor size comes into equation and not just your numerical aperture and the size of the minimum feature you want to resolve?



The rule goes the opposite way: a compact can't match a large sensor camera for shallow DoF and diffraction-limited resolution (which is a different matter altogether, unrelated to anything above, but equally important), because the focal length and the F-number of a lens required for such feat become impractically low.

That being said, a 6x crop compact stopped down to f/8 has the same NA as full frame at f/48, so you may struggle to find a lens capable of that. But at just 2x crop on 4/3 systems there are lenses that go down to f/22.

RoGeorge:
IDK, see these comparative pics (not mine):
https://petapixel.com/2019/07/12/does-sensor-size-affect-depth-of-field-the-definitive-answer/

magic:
Well, you said that it matters ;)

The pics show once again that stopping down FF to f/5.6 produces similar effect to MFT f/2.8, as expected.
MFT f/16 would be matched by FF f/32 and FF f/16 by MFT f/8, but these variants are not shown.

RoGeorge:
Sorry, it was you who used the word "matter", not me.   :P
What I was talking about is visible in that comparison article linked above.

For any pair of two pics taken with the same f-stop and the same framing, but with different sensor size, look at the middle plank, and then look at the last plank:
- the middle planks are perfectly in focus no matter the sensor size
- the last plank however, is sharper for the pic taken with the smaller size sensor

If it were to compare with an even smaller than a 3/4 sensor, like a webcam sensor or a phone camera, then the smaller sensors will show the last plank even more sharper, almost as sharp as the middle plank.

For me that's a fact, visible in the pics, won't gonna argue about.

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