Every digital image has a secret identity.

The big difference between your digital photos and a CIA operative is that it's pretty easy to discover the secret identity of a digital photo.

This not-so-secret information is called EXIF data, and it's encoded in every photo that you take with your digital camera.

Think of it like a barcode on a package: in the same way that the barcode uniquely identifies the product, EXIF data uniquely identifies an image.

But how can EXIF data improve your photography? Let's find out.

Common Camera Settings

There are two principal actors in the photos that you take: aperture and shutter speed.

Aperture is a measure of how wide your lens opens, and shutter speed is how long your camera's shutter stays open to expose the digital sensor to light.

All digital SLR cameras and some compacts let you manually control aperture and shutter speed.

The best way to learn what impact these two features have on your photos is to tweak the settings and see the effects.

With film, there is no way to tell what the aperture and shutter speed are set to for any given image. If you want to keep track, you have to write down the numbers on a notepad for every shot you take.

Not exactly convenient.

On a digital camera, the EXIF data takes care of this for you.

Permanent Setting Storage

Every time you take a photo with a digital camera, the camera automatically saves the aperture, shutter speed, and a variety of other settings.

This EXIF data is permanently attached to the photo, so even when you transfer it from camera to computer the data is not lost.

Once you open the photo in your image editor of choice, you can choose to view this EXIF data any time you want (even a year later).

Here's why this is such a powerful learning tool: you can easily review all of your camera settings for every photo you take.

Learning From EXIF

Example one: you take what you think is a great photo of your daughter playing in the living room. You check the photo on the computer and the entire shot is blurry.

Why? Check the EXIF data and note the shutter speed. It was probably too slow to get a clear shot of your daughter in motion.

Example two: you take a photo of your friend in front of a fountain. It looks like the water is spouting from the top of his head.

The EXIF data shows that your aperture was set to f/11. This aperture ensures that both the friend and the fountain are in clear focus. A different aperture setting would have kept your friend in focus but blurred the background.

While you can learn a lot from mistakes like these, pay special attention to photos that are successful.

Check the EXIF data often for photos that you love, and you might find some camera settings in common.

In the future, you can manually set your camera to your "favorite" settings and capture more photos that are keepers.

There you have it.

EXIF data just helped to improve your photography.

Chris Roberts dispenses practical plain-English advice and information about digital SLR cameras at the Digital SLR Guide. His 5-week ecourse in digital SLR technique helps beginners get the most out of their digital SLR cameras.