Improving Digital Photos of Maps & Prints
by Helen Glazer, Creative Director, George Glazer Gallery

Copyright © 2001-2014 by George D. Glazer. All rights reserved. No part of this document may be reproduced in any form or by any means without written permission of the author

Setting up your camera

When the front of the camera lens is parallel to the picture, skewing is less of a problem. To set up the camera, use a tripod or tabletop copy stand, and a little carpenter's level that you buy at a hardware store. You place the level on the plate of the tripod or copy stand to make sure it is level, and then place the level against front of the lens to make sure it is level in that respect, too. Then you want to aim your lens directly at the center of the map.

What software do I need?

Adobe Photoshop is the image-editing program we use here. However, there are other programs that have the features we mention here, such as a simpler, less expensive version called Adobe Photoshop Elements. We downloaded the free trial at and can highly recommend it for the average consumer. Of course if you already have full-featured Photoshop available, that will do everything you need.

Fixing a skewed map--first, rotate

The first thing you need to check with a skewed map or print image is whether you need to use the Rotate command. Draw a rectangular marquee on your image and see if at least one of the sides lines up. If none do, rotate until at least one side is aligned correctly. Please note that when you rotate the image the background color will show around the edges, so you'll probably want to set it to white on the tool palette before you begin. You can rotate an image by any number of degrees at a time, clockwise or counterclockwise. Start with 1 degree at a time. You can fine tune it by rotating it as little as 0.1 degree until it is straighter.

Sometimes rotating is all you need to do. But rotating is not going to be enough to fix skewed images, that is, ones where all four corners are not right angles. First drag the corners of the window out so you see your map against a gray background. Photoshop and Photoshop Elements has an "Edit: Transform" feature with a "Skew" function where you can drag the corners until the image is rectilinear. You might end up with slight bowing (curvature or bulging) iif the original map was very large. That can also be fixed in Photoshop with the Lens Correction filter. Photoshop Elements also offers a way to fix bowing or its opposite curvature.

Now you can use the Crop Tool to crop the map to the edge or to the plate mark. Enlarge the view first if you need to in order to see precisely where you want to crop.

What file format to use

While you're working on an image, you'll want to save it periodically to preserve your work. Your digital camera may have produced the image as a JPEG. If you are going to be re-saving your image more than once, I recommend before you start, save it as a TIFF or a Photoshop file (.PSD), because each time you save an image as a JPEG, the file size is compressed and some data is lost. TIFFs and PSD files have larger file sizes, but no loss of data from save to save. At the end of the process, when you have the TIFF of the map exactly the way you want it, you can save it as a JPEG if you want to post it on the web, send it as an attachment to an e-mail, or other purposes for which you need a smaller file size than a TIFF. Any image program can open a TIFF, but you probably need Photoshop to open a PSD file, so keep that in mind for long-term storage.

Quick and easy enhancements to digital photos and scans

Aside from that, you should take advantage of a feature called Adjust Levels (in the Brightness and Contrast menu in Elements, in the Image menu of Photoshop). When you open that you'll see a little bell-curve type graph with three sliders at the bottom. To start, move the black slider left, until it points to the left end of the bell curve. Move the white slider right, until it points to the right end of the bell curve. Note how the brightness and contrast dramatically improves. Other useful commands are the Hue, Saturation and Lightness sliders, especially with color maps. The other one we use all the time is Unsharp Mask in the Filters menu, which, contrary to its oxymoronic name, sharpens images. Set the Radius to 1.3 and the Threshold to 8 to start with, and then slide the Amount slider to the largest number between 1 and 200% until the image is sharpened without creating white haloes around the lines on the map. (But avoid the Sharpen command, which won't have the desired effect. Sounds strange, we know, but that's how it works.)

Learning advanced techniques

Finally, Adobe's "Photoshop Classroom in a Book" is well worth the price to work through the tutorials and really learn to take advantage of some of the features of this powerful program. is another excellent site on which to find sequenced video tutorials. Many things are possible with Photoshop, for example scanning or photographing two halves of a large map or print and piecing them together seamlessly. Take a look at our Catalan Atlas page, where each map was pieced together from four separate scans!

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