Digital Focus: Exposure Tricks

All about program modes, bracketing, and best exposure practices.

Dave Johnson

Feature: Improve Photos by Varying Exposure

The heart and soul of any photograph--whether taken with a film or digital camera--is exposure. The goal of every digital camera is to expose a scene for exactly the right amount of time, thus getting the perfect amount of light on silicon. That usually happens behind the scenes, and we don't have to think much about it. But to get the best pictures, it sometimes helps to take an active role in setting exposure.

Get to Know Your Program Modes

Many digital cameras come with a slew of program modes designed to provide the optimum exposure in special situations. Knowing the best time to use each one can dramatically improve your pictures. In fact, you can shoot in your camera's program modes 90 percent of the time and get great results. Here are some of the most common:

• Action. This is what you want when you're trying to capture fast action, like a sporting event. The camera shoots at the fastest possible shutter speed, and selects an aperture to match.
• Sand and Snow. Perhaps the most underutilized mode, this overexposes your photo a bit since a lot of bright sand or snow in the background will tend to trick the camera into underexposing the shot.
• Night. You'll want to use this setting to capture as much detail as possible in dim lighting or at night.
• Portrait. This mode increases the aperture to blur the background and draw attention to the subject.

Try Some Bracketing

There will probably be times when you don't want to shoot in a programmed or automatic mode. Tricky lighting situations, like a partly cloudy day when there's lots of contrast, can wreak havoc with a camera's logic. But instead of switching to manual mode, try a trick the pros use: Bracket your exposure by taking the same picture several times, varying the exposure by about half of a stop each time. The easiest way to do that is to use the exposure compensation dial (usually abbreviated EV on the camera).

Suppose you're at the zoo, taking a picture of a white tiger against a dark backdrop of leaves. I'd assume that the camera's exposure meter would measure the dark background and end up overexposing the smaller and brighter feline. Consequently, I would be inclined to take one picture using the camera's automatic control, but then quickly set the EV dial to-5 and take a second "insurance" shot. Not sure what effect a very different foreground and background might have? Cover all the bases by taking three shots:-.5, +.5, and automatic. After all, it's a digital camera, so you're not wasting any film by capturing multiple instances of the same scene. And it's better to grab a few shots quickly than waste time examining each picture on the LCD--especially if your subject is moving or seems restless.

Some digital cameras have an auto-bracketing feature that lets you snap all three exposure variations, one after the other, just by pressing the shutter release once.

In the Spotlight

Depending on your digital camera, you might have another trick up your sleeve. Remember our friend, the white tiger? Instead of using exposure compensation to account for different foregrounds and backgrounds, you could switch to the spot meter and set your exposure for just the most important part of the picture.

By default, most digital cameras use an exposure meter that takes an average of all the light in the scene and uses that to calculate the shutter speed and aperture. But some cameras use some sort of matrix meter to measure light in several different zones. A spot meter measures the light in just one place--usually a tiny zone in the dead center of the scene. It's not a mode you'd want to use all the time, but it can be a lifesaver when you need to set the exposure based on a small area in the overall composition.

Dave's Favorites: Epson Stylus Photo 900

I've long been an Epson fan--my day-to-day photo printer is a Photo Stylus 1270--and I'm intrigued by the new Stylus Photo 900. Why? This printer is the first consumer-priced ink jet capable of printing directly onto CDs and DVDs.

For a street price of just $200, I found the 900 to be a terrific printer. The six-ink design (a five-ink color cartridge, plus black) renders absolutely superb detail and richness of color, making this one of the best printers I've used for straightforward photo printing. No doubt, you can attribute part of that to the printer's support for Print Image Matching II. When used with PIM-compatible cameras, this feature allows the printer to render images with a deeper tonal range and less noise than would ordinary printers.

The Stylus Photo 900 can print up to 8-by-10-inch photos or, with the included roll holders, create prints as long as 44 inches. I haven't tested super-long prints yet, but I have tried the printer's other trick: printing on CDs and DVDs. Epson includes a special tray with a disc cutout that slides into the back of the printer. That can be a problem--if you keep your printer nestled against a wall, you'll have to pull it away and fiddle with cables to reach the tray loading slot. After that, to make a symmetrical print on the disc you need to precisely line up marks on the tray with a point in the printer. This is the printer's most serious shortcoming: Instead of just clicking the tray into position, you have to line it up by eye. My first few CDs came out a bit askew.

But the hassle is worth it: If you burn your own CDs and DVDs, the Stylus Photo 900 is a blast. You'll need to buy slightly more expensive ink jet-printable discs, but instead of sticking a label on your discs, you get a professional-looking color print directly on the surface. I wish it were easier to line up the CD tray in the printer, but otherwise this new Epson printer is a winner. At press time, I found it for as little as $178 at the PCWorld.com Product Finder.

Q&A: Measuring the Damage Done by Digital Zoom

Is there any way to estimate the loss of effective pixels in your photos when using a digital zoom?

--Steve Young, Southampton, Pennsylvania

Yes, Steve--and it's an easy calculation. A digital zoom eats pixels at a rate that's directly proportional to the magnification of the zoom. In other words, using a 2X digital zoom on a 3-megapixel camera would create an image just 1.5 megapixels in size. A 3X zoom on the same camera delivers an image with an effective resolution of just 1 megapixel.

A digital zoom crops away pixels in proportion to the zoom intensity. A 2X zoom, for instance, captures only 50 percent of the image in the center of the frame, then enlarges each pixel to bring the resulting image back to "full" resolution. But that's deceiving, because the camera has actually used only half its pixels to capture the zoomed image. And what do you get for that loss of pixels? The results look the same as if you'd taken a regular 2-megapixel image and cropped away half of it in an image editor. That's why I recommend ignoring the digital zoom and saving all of your editing for the PC.

Hot Pic of the Week

Get published, get famous! Each week, we select our favorite reader-submitted photo based on creativity, originality and technique. Every month, the best of the weekly winners gets a prize valued at between $15 and $50.

Here's how to enter: Send us your photograph in JPEG format, at a resolution no higher than 640 by 480 pixels. Entries at higher resolutions will be immediately disqualified. If necessary, use an image editing program to reduce the file size of your image before e-mailing it to us. Include the title of your photo along with a short description and how you photographed it. Don't forget to send your name, e-mail address, and postal address. Before entering, please read the full description of the contest rules and regulations.

This week's Hot Pic: "Where's My Lunch?," by Stacy A. Niedzwiecki, Rockford, Michigan

Stacy is no stranger to our winner's circle, and this month she brings us a very hungry-looking little bird. She says: "Somewhere in my backyard was one busy momma robin. Her little guy lives in a pine tree, and I could hear him yelling at mom all afternoon. I set my Olympus C-3040 on the macro setting with no flash. It was a cloudy day, so I had to bump the ISO up to 400 to make up the difference. Under momma's watchful eye, I made clucking sounds to get the little guy to pose."

We want your feedback! Send your comments, questions, and suggestions about the newsletter itself to comments@bydavejohnson.com. If you have a question that you'd like to see answered in the weekly Q&A, send it to question@bydavejohnson.com.

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