At our Atlanta photo lab, we get asked daily if an image will look good as a large print, and we suggest doing a mag test. Then their eyes glaze over and say “mag what?” I get it; I did the same thing when we opened our photo lab a few years ago. But now I get it and I want to help you get it, too.
What is a mag test? A mag test is used to check an enlargement for how well it will hold up to an enlarged size. Mag is short for magnification, as that is what you are doing: magnifying your image.
Doing a mag test will allow you to select a very specific section of your image, cut out that section at the exact size it will be in your final print, and make a test print. If done properly you will be able to judge if that section is sharp, or sharp enough for viewing distance.
Typically an 8×10 will be large enough to test with. Personally I will do an 11×14, but that is just me. Since an 8x10 or 11×14 is drastically less expensive than a 30×40 or 30×90, it is a great test to make sure your image will hold up to the size you want.
So let’s walk through the steps in Photoshop to illustrate how to properly order a mag test from our Atlanta photo lab.