The Digital Darkroom
Correcting Distortion In The Digital Darkroom

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Photos © 2001, Darryl C. Nicholas, All Rights Reserved

Remember in the old days how you used to tilt the easel when you made a print under the enlarger if you wanted to correct for some optical distortion? Well, there is a way to do something similar using Photoshop when you are working in the digital darkroom.

Recently I was asked to photograph a piece of needlepoint that had been framed under glass. My daughter had made the needlepoint, so there was great pressure on me to do it right.

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In the old days when I had to photograph a picture that had been framed under glass, I would set up twin umbrellas with electronic flash units. Then, I'd position the camera on the center line of the center of the picture and drape the camera in black so the camera's reflection would not show in the glass. All of this setup can take quite a bit of time and even then, you might have to do it over several times to avoid reflections in the glass.

That was then. This is now. I simply laid the framed needlepoint on a nearby table and with a digital camera stood at a sufficient angle to guarantee no reflections and snapped a picture. I stood as far away as I could and still fill the camera's frame when I zoomed in with the lens. By standing a bit farther away than normal, the flash illumination would be more even with less tendency for hot spots.

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In #1 you can see what the picture looked like that I took. Notice that it is illuminated evenly enough and that there is no glare on the glass. Notice, also, that it is very distorted. That is, it is not a nice, true, rectangle.

To correct the optical distortion I loaded the image into Photoshop Version 6.0. Earlier versions do not have the feature that I was about to use.

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In Photoshop, select the cropping tool and drag it through the picture leaving plenty of room all the way around the picture as shown in #2.

Next, in the border area at the top of the monitor, you will find the dialog box for the preferences setting for the cropping tool. This dialog box will not become visible until after you have made a preliminary selection around the picture.

Next, put a check mark in the little square called Perspective. See #3.

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Now, go back to the picture and drag the corners of the cropping tool selection box so that they align up exactly with the four corners of the picture as in #4. Press Enter and enjoy the corrected image, #5.

This little trick saved me hours of work when I was asked to photograph some framed art work at a collector's home not too long ago.

If you'd like help with your Photoshop problems, you can send an e-mail to me care of the magazine at: editorial@shutterbug.net.

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