Digital Focus: Tricks for Tricky Lighting

Compensate for low light, fix underexposed photos.

Dave Johnson

Feature: Compensating for Tricky Lighting

The human eye is a very cool little organ. It automatically adjusts for changing lighting conditions so effortlessly that we expect the same kind of results from our cameras. The reality, though, is that digital cameras aren't nearly so adept. Step into a darkened cellar, for instance, and it takes your eyes only a few seconds to adjust to the dramatic change in lighting, and then a quick glance will allow you to take a mental "shot" of even a very dim corner. No matter how long you wait, however, you'll need a steadying tripod--and a lot more time--to take the same picture with your digital camera. The camera's "eye" will never adjust in the same way to the dim light.

The camera and your eyes differ in other ways, too, as you've probably noticed if you try to take a photo of someone standing against a bright background. Your eyes can see the person fine, but the camera will probably drastically underexpose the subject, since it's being tricked by all the light in the background. This week, let's see how to correct for these kinds of lighting problems.

Fix Underexposed Photos

When you're in the middle of taking a batch of photos, you probably don't want to start messing with arcane camera controls. But unusual lighting can play havoc with a picture's exposure, so it's a good idea to learn how to use your camera's Exposure Value control. The Exposure Value affects how much light gets through the lens when you press the shutter release. Most digital cameras let you adjust this value up or down a bit without worrying about details like shutter speed and aperture settings.

So, suppose you're taking a picture of someone sitting in a pile of freshly fallen snow. After you take the picture, check out the result in the LCD display on the back of the camera. You might find that all that bright, fluffy whiteness has fooled the camera into underexposing the subject. Shoot the picture again, but this time set the EV control to +1, which means, in plain English, "overexpose this photo by one exposure stop." Most digital cameras let you change the EV setting as much as-3 to +3, so you can experiment until you find the right balance for your photo.

Combat Overexposures

Hard-to-shoot situations abound. Let's say you're photographing a person sitting at a window bench with sunlight streaming in from behind, or taking photos at the beach--with lots of highly reflective water in the background. Your subject's complexion can also be an issue; if you're got a dark-skinned person who's wearing very bright clothing, for instance, your camera has its digital hands full trying to figure out the right exposure. In these cases, I switch over to the spot meter. Sure, I could use the EV control, but a better option is the spot meter, which lets me set the exposure for the picture based on the part of the image that is most important to me.

Many moderately priced digital cameras come with spot meters these days. Instead of taking an average light reading across the entire viewfinder, the spot meter focuses on a tiny spot in the middle of the lens and measures exposure there. A spot meter lets you lock in the exposure of someone's face, regardless of the lighting or colors in the background. It's my secret weapon for making sure that I get a perfect exposure right where it counts.

Practice with these two controls, and you'll find that your pictures will begin to look better, with fewer over- or underexposed throw-aways.

Dave's Favorites: Resco Picture Viewer

In weeks past I've written about some of my favorite image viewers for the Palm PDA, programs that let me carry digital images around on my PDA as if it were some sort of electronic wallet.

I use a Pocket PC as well, and several readers have demanded to know what picture viewer I recommend on that platform. Here's your answer: If you carry a Pocket PC and want to use it to show off digital images, look no further than Resco Picture Viewer ($20).

I love this program's interface. A gorgeous, button-laden startup screen lets you choose from among common tasks like Open Album or Browse Compact Flash Card. The program supports more than a dozen file formats, so you'll have no trouble opening JPEGs, bitmaps, GIFs, and even MPEG video on your PDA.

Resco Picture Viewer makes it easy to display images stored on a Compact Flash card--just pull the card out of your digital camera, insert it into your Pocket PC, and you can view your images instantly. Or you can drag-and-drop images onto the Pocket PC from your desktop PC; it's your choice. Either way, Picture Viewer gives you four thumbnails in a filmstrip-style trip across the top of the screen, with a larger view of one image in the main part of the display.

There's lots of other goodies in Picture Viewer, like a screen capture tool and an elaborate suite of structured and freehand drawing tools to edit your images. If you want to show your images like a slideshow, you can even choose an MP3 file stored on your Pocket PC as the soundtrack.

Q&A: How Can a 3-Megapixel Camera Shoot 6-Megapixel Photos?

I have a question about CCDs and resolution. I've been thinking about buying the Fuji FinePix S6202 Zoom. The image sensor is a 3.3 megapixel "Super CCD," with 3.1 million effective pixels. But the camera captures pictures with a resolution of 6 megapixels.

How can you get a good quality 6-megapixel output if the CCD only records 3 megapixels? I don't get it.

--Sandra J., Long Island, New York

An excellent question, Sandra. It's clear to me that you have seen right through an insidious marketing trick. There are a few cameras on the market--mostly from Fuji--that claim to deliver more pixels in the final image than the CCD itself is capable of capturing. But the bottom line is this: At heart, they're still just 3-megapixel cameras, and the end result can't possibly have the resolution you'd get from a 6-megapixel camera.

To create a "Super CCD," Fuji arranges the sensors in a unique pattern on the silicon, allowing for more image sensitivity and better resolution--in theory. That sounds good, but I've tested several of Fuji's Super CCD cameras over the years and I can tell you that those cameras are writing checks its resolution can't cash.

When viewing pictures taken at maximum resolution, I can easily find digital noise at 100 percent magnification that wouldn't be apparent unless you zoomed into 200 percent with many other cameras. Worse, Super CCD pictures sometimes sport a noticeable mosaic pattern that betrays the fact the camera is overreaching its resolution capabilities.

Here's my advice: If you want a 6-megapixel camera, buy one. But don't mess with a 3-megapixel camera that is masquerading as more than it really is.

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 $10 and $100.

A gentle reminder, folks: We disqualify some really wonderful pictures every week because the submissions don't follow the rules. Be sure to include everything we ask for in your e-mail message, including a description of your picture and your complete contact information, or your entry is wasted!

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 regs.

This week's Hot Pic: "Field of Flags," by Thai N. Strom, Stockton, California

About this week's Hot Pic, Thai says: "It was taken in Lodi, California, on August 2, at the closing ceremony of the display of the Moving Wall, a replica of the D.C.-based Vietnam Veterans Memorial. After a very emotional event, I came upon this touching scene of a little girl happily playing on the Field of Flags."

Hot Pic of the Month

Each month we choose one of our weekly winners to be the Hot Pic of the Month. Picking a winner for October was challenging, but in the end we went with "Cobblestone Rose," Angela Covington's portrait of a rose among cobblestones. As always, congratulations to all the other weekly winners. Keep up the good work!

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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