Why does DPI Matter?

[metrologist]

Most of the images we are looking at are untreated JPEG images from photoshoots - what comes out of the camera. It's basically a photo archive, but there are also many derivative compilations, not generally considered a final deliverable for any sort of publication.

The marketing folks would be going here to get source images for use in web media, PDF, and other...

I think it is a silly request.

[rsfoto]

Here are two versions of the same photo shown side by side: one is 300 ppi, and the other is 10 ppi.

10 ppi on the left, 300 ppi on the right


The individual files are below.

That is not right as you are comparing apples and oranges.

OK, what you did is resize that crop to a different size in PPI and then resized it again and so of course it looses resolution ...

You can see that in your 2 images which have a completely different size.

regards Rainer

[tooki]

Here are two versions of the same photo shown side by side: one is 300 ppi, and the other is 10 ppi.

10 ppi on the left, 300 ppi on the right


The individual files are below.

You didn’t understand the original query. He wasn’t asking about scaling an image. It’s only about the resolution metadata tag in a file. Cute capybara, though!

I think there is a reason for the marketing guy to request 300dpi images even for web material, as those images would look nicer on a device with high DPI display (like recent iPhones, or people with 4K monitors - I have both, and it does make a difference.)

Nah, it's a holdover from the print era, plain and simple.

The pixels on those HiDPI monitors are so small that pixel-for-pixel display of traditional user interface would be too small to read or use. So for those HiDPI monitors either they have to prepare a vector image or higher DPI image to display pixel for pixel, or allow the image scaling algorithm to ruin the entire user interface. HiDPI sort of forced some print era solutions to resurface, as the screens now have similar dpi resolution as the printers.

We aren't talking about user interfaces. We're talking about marketing photos.

The same still stands. Showing a 96ppi image on a 162dpi screen (iPhone 3GS) is okay, but on a 364dpi acreen (iPhone 4 and up) it looks like crap due to either being to small when shown pixel for pixel, or blurriness or jaggedness from pixel doubling. The same for a 85dpi 1080p monitor versus a 170dpi 4K monitor. Using high enough ppi source image allow the browsers on standard monitors to scale the picture down while HiDPI browsers still have enough information to reproduce a crisp smooth HiDPI image.

Who cares? This still has nothing to do with the discussion at hand!!

[Tom45]

You didn’t understand the original query. He wasn’t asking about scaling an image. It’s only about the resolution metadata tag in a file. Cute capybara, though!

The original query was in effect, does the dpi setting mean anything?

I say the dpi setting in the file is merely semantic metadata and how it's used depends on the application processing the image. For example, Paint is not going to care if the image is set to 72, 96, or 300dpi, it will look the same... amiright?

And then others said that a larger dpi(ppi) is better than a smaller value.

My example was to show that the number of pixels is what is important in determining the image quality, not the dpi setting in the file's metadata.

Tom

[tooki]

You didn’t understand the original query. He wasn’t asking about scaling an image. It’s only about the resolution metadata tag in a file. Cute capybara, though!

The original query was in effect, does the dpi setting mean anything?

I say the dpi setting in the file is merely semantic metadata and how it's used depends on the application processing the image. For example, Paint is not going to care if the image is set to 72, 96, or 300dpi, it will look the same... amiright?

And then others said that a larger dpi(ppi) is better than a smaller value.

My example was to show that the number of pixels is what is important in determining the image quality, not the dpi setting in the file's metadata.

Tom

Again, I think you misunderstood the query. We all know that the pixel count is what actually provides detail. The question was about what the DPI setting (i.e. the metadata tag) does, and the fact is, that’s app-dependent, and marketing weenies don’t understand it.

I don’t see where anyone said that a higher DPI is better. Without a specific context, such a statement is meaningless anyway.