DIY Network

Macro Photography: Exposure Control and Bracketing From "The Whole Picture" episode DTWP-102

In "Lesson 3" of DIY's macro photography series, Erin Manning explains how to take control of your photography by turning off the auto-exposure feature and making some of the decisions yourself. One of the techniques you can employ is known as bracketing--the practice of taking multiple photos of the same subject, at varying exposures, then selecting the one with the best results.

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	Try getting the perfect exposure by bracketing. Adjust the exposure up and down a few increments until your image is not too dark or too bright. Play around until you get the perfect exposure.

Taking Your Camera Off "Cruise Control"

When the camera is on auto-exposure, its computer makes the exposure decisions for you. It analyzes the light on the scene and sets the camera's shutter speed and lens opening to what's best for the overall picture based on calculations and pre-sets. The advantage of using auto-exposure is that it makes it really easy to take good pictures without a lot of work on your part. But it may not be what you want if you're goal is to take great pictures. To get great pictures, you'll have to start making some of the decisions yourself.

Improving Your Odds Through Bracketing

If many of your pictures have areas that are too dark or light, remember the camera decided what's best overall and didn't compensate for the areas that were way outside what it thought was the average amount of light. To fix this problem and take full control, you can turn off all the auto-exposure functions and then just either guess at the right exposure from looking at your LCD or employ a technique known as bracketing.

One problem encountered with digital cameras is that what you see in your LCD screen isn't always exactly what the camera records. Additionally it's sometimes hard to see that LCD screen when you're working outside.

Bracketing is a trick pros use to make sure they get the right exposure. The technique is essentially taking the same photograph multiple times using differing light exposures. Then you can select the best from among the different results you get. With a digital instamatic, an easy technique is to take the first picture on auto-exposure--letting the camera's computerized sensor pick its best guess at the settings. Then manually shoot one image with a little more light than the auto function used, then one with a little less light. Then you'll have a range of images to choose from.

To try this yourself, try shooting the same picture three times. For each version of the picture, change one of the things that determine the exposure. The two main things that determine good exposure are the aperture (the size of the lens opening) and the shutter speed (the length of time the shutter stays open). By changing either of these, you increase or decrease the amount of light that hits the camera's sensor. It's not really complicated if you know how to use your camera's settings.

	Figure A
	Figure B

• Before trying to bracket, check your camera's manual and familiarize yourself with navigating its menu system (figure A). Film cameras and more advanced digital cameras are more versatile because they have many exposure adjustments. But most point and shoot digital cameras only allow you to change the sensitivity of the camera's sensor. In your manual, this may be called exposure compensation.

• To bracket, or use exposure compensation, take your first shot on auto exposure. Then, turn the camera to manual (figure B) and navigate the menu to the exposure compensation setting. Adjust up or down one increment. Make sure you hit the ok button to lock in the setting. Then take your second picture.

• Repeat the process adjusting the exposure in the other direction before shooting the third picture. That's all that bracketing is. It simply makes it more likely that you will get the perfect exposure.
  

• On cameras where you can adjust the lens opening, like the ones the pros use, shoot your first shot on auto and then switch the camera to manual. Then open or close the lens opening before taking your next shot.

• When you're done be sure to set the camera back to automatic.

• Pros usually use a light meter (either hand-held or one built into the camera) to help them decide how much to adjust their exposures--either by varying aperture or shutter speed.

• One other way you can compensate for the exposure is to reflect a little extra light on your subject. Take your first picture and then just put a piece of white paper under the subject to bounce some extra light onto it. It kind of brackets the exposure in one direction.

RESOURCES :

PC Photo magazine
Website: www.pcphotomag.com
Online version of the magazine devoted to digital photography and related technologies.

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