Meant to come back and make this comment. I've made a LOT of photographic prints at 150dpi and have never once had any comment other than "that looks amazing".
I used to think 300dpi was "bare minimum", having studied computer graphics in college and Nyquist limits and all that. And then one day my father printed a 640x480 cellphone camera photo as an 8x6 and... it looked fine. I was blown away.
And then I finally remembered: human eyes don't detect absolute light value, we can only see relative differences in light values. Gradients don't provide enough change to see the edges between colors. You can see it on a computer screen because the screen amplifies the contrast of the image (another old lesson I eventually had to relearn so as to compensate when making prints of digital photos).
Nobody knows what resolution you print things when they see the print. If the average joe "knew" how the photo was made, they might scoff at it. I guess people think that craft requires fine precision at all steps of every process. Certain craft does, but some other craft requires randomization and binning, and others have diminishing returns on extra effort. So I find it kind of fun to print low-resolution photos. Feels like I'm winning a game against overly officious critics.
> Gradients don't provide enough change to see the edges between colors. You can see it on a computer screen because the screen amplifies the contrast of the image (another old lesson I eventually had to relearn so as to compensate when making prints of digital photos).
> Nobody knows what resolution you print things when they see the print.
Well sure, you're right about the gradient thing, but what if you have an image with some really sharp, contrasted edges?
Just anecdata, but my family and I were walking through a seasside town a while back and ended up in an artist's shop. Took a look at some photographic prints on the wall (going for $50-$150+, as "artisan" stuff often does), and I had to call my partner over to look at them because I couldn't believe they were all pixelated! Some of them quite badly. I was about 18 inches away from them, I guess, and they looked to have been printed at about 100 dpi. Sure, you probably don't need 300 DPI for large wall prints, but I'd rather have a margin of error and not have that happen to one of my prints. Most people aren't likely to notice flaws in printed images, and are even less likely to tell the owner if they do.
I guess it's possible the shots sent to the printer were badly compressed JPEGs, but that seems unlikely.
It not only depends on the image content, but how you send the image to the printer.
Print engines can apply nearest-neighbor interpolation which results in visible, blocky pixels. If they'd upsampled the image with lanczos or another higher-quality algorithm before sending it to the printer, it would have looked like it was just a touch out of focus.
I used to think 300dpi was "bare minimum", having studied computer graphics in college and Nyquist limits and all that. And then one day my father printed a 640x480 cellphone camera photo as an 8x6 and... it looked fine. I was blown away.
And then I finally remembered: human eyes don't detect absolute light value, we can only see relative differences in light values. Gradients don't provide enough change to see the edges between colors. You can see it on a computer screen because the screen amplifies the contrast of the image (another old lesson I eventually had to relearn so as to compensate when making prints of digital photos).
Nobody knows what resolution you print things when they see the print. If the average joe "knew" how the photo was made, they might scoff at it. I guess people think that craft requires fine precision at all steps of every process. Certain craft does, but some other craft requires randomization and binning, and others have diminishing returns on extra effort. So I find it kind of fun to print low-resolution photos. Feels like I'm winning a game against overly officious critics.