Digital Focus: Photo Resizing Tricks

Feature: Resizing Photos in One Dimension

Sometimes you take a picture that almost makes you happy, but it has some problems. That's what happened to me on a recent scuba trip. I managed to salvage one picture in particular with a little clever editing. In the end, what made all the difference was modifying the picture's aspect ratio. In other words, I stretched it.

Stretching photos is usually not something I recommend; but, as you'll see this week, there can be good reasons to give it a try.

If you want to play along at home, save the image file and open it in your favorite image editing program to follow my path from the original, unsatisfying image to the final, stretched version.

Sizing Up the Problems

The picture was taken as a diver swam overhead, passing between my camera and the surface. We were in a cave filled with thousands of fish, and the sunlight created a pretty silhouette of the diver's legs.

Unfortunately, the concept sounds nice--but the actual photo I captured is something of a train wreck. Another diver bumped into me just as I took the picture, and my carefully planned composition was ruined. It's also too dark and the diver's silhouetted fins blend into the shadows.

Crop Out the Distractions

The first thing we can do to resuscitate this picture is to recompose it by cropping. Click the Crop tool (it lives in the third cubby from the top in the toolbar on the left side of the screen), then drag a crop box around the diver that eliminates most of the background and makes that pair of legs the real focal point. You should now have something like this; to apply the crop, double-click anywhere inside the box.

Now that we've eliminated most of the surrounding bits, we need to do something about the contrast. Don't get me wrong; I like the dark silhouette, and I don't want to lose the overall dark tones of the cave. But I want to lighten the picture just enough so that the fins are more clearly defined.

Fix the Lighting

There are a lot of ways to improve the overall lighting and exposure, but I think the Curves tool will suit this image best. Using Curves, we can "remap" the light values at each pixel in the picture. Open the Curves tool by choosing Adjust, Brightness and Contrast, Curves. By default, the curve is a straight line, which indicates that nothing has been changed. If the curve is, well, curved, reset it by clicking the Reset to Defaults button--the curved arrow at the top right of the dialog box.

Now grab the curve and stretch it upwards to increase the brightness. When you like what you see in the preview box, click OK. It's a matter of taste, but I like these values.

Resize in One Dimension

By this point, I was mostly happy with my picture--but it wasn't dramatic enough. I wished I had used a wider lens, or the diver had longer legs. I wanted more diver in my picture!

The solution is easy. Choose Image, Resize. Usually, when you resize a picture, you want both the width and height to change together, or the picture will look like a funhouse mirror. But in this case, let's decouple that relationship.

Remove the check mark from the box marked Lock aspect ratio, then set the dimensions to Percent using the drop-down menu in the Pixel Dimension section of the dialog box and set the height to 100. Set the width to 130 and click OK. You'll get an image that looks something like this, which is a lot closer to what I had in mind when I took the picture.

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