I'm doing some UI in Maya for a mobile app and we are just exporting finished frames (not animations or anything) to use. Now I need a new set of all our assets (images) but re-sized to fit a different resolution. I figured it would be simple to just take them into Photoshop and re-size them appropriately but a colleague claims that will ruin the quality.
Now granted, the images are so small to begin with I find it hard to believe the quality loss would be noticeable if it exists. My bigger qualm is if this is even true... He want's me to keep exporting the frames out of Maya with different settings to get the lower resolutions. Could I just use Photoshop or is he right?
My inclination is to agree with you--so long as you are only shrinking the images, of course (as the title of your post implies).
However, it's possible that if your images have thin, precise lines, etc., the process of downsizing and resampling will impact the crispness.
But here's the main point: why not just test it? It should be a simple enough process. Just downsize one or two images, and also re-render them at the lower res, and then compare the results. If you can't tell the difference, then who cares? If you can, well, then you should re-render.
Frankly, though, if you need pixel-precise lines, you should be painting them directly in a painting or illustration program, not in 3D. Of course it's impossible to gauge without seeing examples of your screens.
Finally, note that if you need to render out two different resolutions of the same series of images, you could do this fairly straightforwardly (and automatically) by using render layers. Have one layer for the larger res, and create a second one with a render layer override on the resolution attribute in the Render Settings window. Then whenever you render, you'll get both images automatically output.
Ah good thinking! Sorry for the delayed reply. The project ended up getting postponed but I'm sure it's going to come back up soon. When it does I'll definitely be doing some tests. Thanks for the reply.