I work in analog/film photography (B&W) and all of my photos are created in the darkroom. This will be my first time applying to an art festival and I wanted to find out what would work best for my submission photos. Would it be better to photograph my prints or get scans made of the prints and submit those?
Scan them. You'll get better results than rephotographing them. They will, of necessity, be submitted as a 1920x1920 pixel image. If you have 8x10 images, it will be no problem to scan them, Scan them as 16 bit B&W images unless you have toned prints, and in that case scan as color images to preserve the toning or paper base color.
If your images are larger than 8x10, scan them in sections and use photoshop to stitch them back together. I've digitized some older B&W pieces I've done where I can no longer find the negative. Photoshop Elements has this as a direct function.
You'll need to do some minor tweaking in Photoshop to correct gamma mismatch on the deep blacks and pale highlights. You'll need to make sure your monitor is calibrated. There's no online color calibrator but gray scale calibration is available with this test target https://www.photofriday.com/info/calibrate. You'll need to see all 26 steps on the target, and distinguish tones on the shadow/highlight targets. The calibration is a bit counterintuitive, with brightness adjusted to separate the black targets, and contrast to adjust the brightest targets. This won't adjust color but it gets the gray scale settled. Ideally, use an optical calibrator but for now use the PhotoFriday target.
Scan so the longest image has about 3000 pixels on ot, 8x10 would scan as 2400x3000 pixels. That gives you room to work with it in Photoshop. When done tweaking the image, reduceimage size to 1920 pixels on your longest dimension. Use the Canvas selection to expand the short side to 1920 pixels, using black for the canvas. Save as a JPEG with just enough compression to get the file size under 2.2M. The ZAPP requirements may have changed but I believe that's the maximum size they take at this time.
Thank you Robert. This is helpful. Glad you mentioned the toning.