Frequently Asked Photo Questions for November

Have a question about digital photography? Send it to me. I reply to as many as I can--though given the quantity of e-mails that I get, I can't promise a personal reply to each one. I round up the most interesting questions about once a month here in Digital Focus. For more frequently asked questions, read my newsletters from August, September, and October.

Taking a Group Portrait

I need to take a picture of a group of people. I have seen photos of groups where everyone looks sharp whether they're in the first line or all the way in the back. What do I need to do to get uniform sharpness throughout the photo like that?--Mo Ashkanani, San Francisco

You'll want to maximize the depth of field, Mo.

If you're taking group photos with the camera set to Program or Auto, you don't know what you're actually getting. So switch to Aperture Priority and dial in the biggest aperture (smallest f-number) you can. Then, if you have three or more rows of people in your group, focus on the middle row, so you ensure a region of sharp focus in front and behind the primary point of focus. If you focus on the front row, you're wasting precious depth of field in front of the group, where no one is standing.

You can read about more depth of field tricks in "Four Ways to Get Stunning Depth of Field."

Find Duplicate Photos

Over time, I've somehow ended up with duplicate photos on my computer and external hard drives. Is there a program that will identify duplicates and display them so that I can delete the dupes?--John Schlesinger, Lawrenceville, New Jersey

There are a lot of programs around that will identify and eliminate duplicate files, John. I've used Duplicate Cleaner. It's a free utility that runs on Windows XP, Vista, and Windows 7. Depending on how you tell the program to run its search, Duplicate Cleaner can identify files that are identical based on content--which is ideal for photos--or it can just find files with similar file names. The program makes it easy to locate and eliminate duplicates.

Making Double Exposures

Can I create a double exposure on the still mode of my Sony camcorder? How?--Holly Bower, Spencer, Iowa

There are very few digital cameras that have the ability to double-expose a photo, and I don't know of any camcorders that can. But you don't need to do it "in the lens," so to speak--just take two photos and combine them in a photo editing program using layers. That way, you can control the opacity of the top layer and get exactly the mix you're looking for. You can learn how to do this in "Improve Your Photos by Editing with Layers."

Image Stabilization and Tripods

Should I disable my lens's image stabilization feature when using a tripod?--Stephen Henry Puttock, Thailand

Generally, yes. If you leave image stabilization turned on while the camera is mounted on a tripod, then the camera might interpret artifacts in the sensor's data--like digital noise--as motion, and end up compensating for an effect sometimes called "ghost motion." And that can result in adding blur to a photo that would otherwise have been perfectly sharp.

For more PC news, visit PC World. Story copyright PC World Communications, Inc.