I'm not really into product photography. I'd have guessed you'd do a separate macro/close-up shot to show off the fabric/texture. Anyway, big resolutions are good for landscape photography too, if your target is an A3+ or an A2 print. Also it's good to have some room for cropping and downsampling. But if your camera has at least 24Mp+, you'll be more concerned about DR and high ISOs (in case of night/astrophotography). I do pixel-peeping on my landscape shots, but I'm very well aware I'm most likely the first and last person who views my shots magnified to 1:1. Everyone else sees them printed, or on a relatively small screen, far below 30Mpix of my 5DIV.
With the full frame format, I think 50Mp cameras are already scratching the limits of what can possibly be needed without losing quality. Higher resolutions are better fit for medium format sensors, IMO. I'd be interested to see something like 40-45Mp EOS 5R from Canon, but say 60Mp would be an overkill, even the Canon's glass wouldn't cope.
A lot of this has to do with the combination of image viewing size and viewing distance. When you look at a billboard while driving down the highway, it’s huge, but you see from so far away, that the Rez is actually low, and the halftone dots are the size of golf balls, or even a hardball. Here in NYC, in the subway, the Ad posters on the walls have halftone dots that are a good 1/16”.
The truth is that for much work, resolutions isn’t as important as Pixel peepers think it is. A friend of mine was a fashion photographer, and together, we were some of the very first in that field to go digital. Resolutions for Hasselblad backs were 4MP. It worked. Gradually they became higher, and customers began demanding the highest resolutions, just because...
But even when dealing with the 33MP backs back then, the retouchers would drop the resolution to half that as soon as the image files arrived. The customers didn’t know, nobody told, and they didn’t notice.
Since my friend, several years ago, retired from fashion, he’s been living in the Midwest, where he travels around in a mobile home, and does landscape photography, which he prints on a 48” Canon inkjet, sometimes printed in a larger size by a lab when needed. He sells these to companies that put them in lobbies. They are very sharp, and he still just uses 33MP backs, which are more than enough, because these large images are viewed from several feet away, at the closest, as are large prints in general, except sometimes when viewed in a gallery.
