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.
First you are going to crop and resize the image to the size you want your final print to be. I want this panoramic print to be 30×90. Since I shot it with a Widelux 35mm panoramic film camera, then scanned it, I really want to make sure the film grain will hold up to that size.
Once your image is properly sized, select the rectangular marquee tool.
In the options bar at the top of the screen look for style and change the drop down menu to fixed size.
To the right of the drop down menu are a width and height box that you will enter the size of your test image, for this example it will be 11×14.
Now click anywhere on your image and a selection box will appear that is set to 11×14.
Click within the selection to move the selection over the area you want to check for sharpness, color, pixelation, or whatever.
Now make a copy of the selection by going to the menu bar and selecting Edit>Copy.
Now go to File>New and open a new document.
An options box will appear and in the drop down box for Presets, select clipboard and hit ok.
Once you hit ok, a new window or tab will open that is blank and presized to the size of the selection that was copied.
Finally, go to Edit>Paste to place the selection into the blank image.
Check your image size before saving the file and make sure it is sized properly.
You will now have an 11x14 section of your image that can be printed and judged before you make your final print.
If you are unable to make this work, or just don’t have the time, we can do it for you. For a $15 fee we will resize your image and create the mag test for you. Call for details.