How to do a mag test

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.


How to prepare your images for custom print sizes.


I often get asked about printing a custom size that we do not offer.  Let me show you how I do it after I have set the crop I want.

First, size your image to the size you want the image to be.  In Photoshop go to Image>Image size and set the width or height you want your image to be. Typically I am only adjusting one of the dimensions (my critical dimension) and letting Photoshop set the other.  In this example, I needed my height to be 5.5 inches, and I will work with whatever the width is.  Make sure your resolution is not set to 72 Pixels/Inch as we mostly print at 300 Pixels/Inch.

image resize

Set your custom image size and make sure you are NOT at 72 Pixels/Inch.


Next, determine what print size we offer that is just larger than your image size.  Now go to Image>Canvas size and change the width and height of the canvas to that size. The center square in the anchor box should be automatically selected, but double check and make sure.


Canvas Size

Set your canvas size, and make sure the center square is selected for the anchor box.


If everything goes according to plan you should end up with a final image that is sized to print with a white border that should look something like the image below.


FInal resize

Your image should look something like this.


At this point I would be done, and I would print it with the lovely white border and leave it that way. But some people do not like borders and want truly custom print sizes.  So if you do not want a border, and want us to trim it rather than trimming it yourself, let’s look at what you need to do in ROES to get your image trimmed to your custom print size.

In ROES, go to your shopping cart, select Special Instructions and type trim to image.  Simple as that. Now complete you order and we will trim it before we package it. Trim charges may, or may not, be extra.

Call us at 404-885-1885 for more details or for assistance.


Trim to image

Just ask us to trim it, and we will, no problem.


Hope this helps!

Good luck shooting and happy printing!