Page 1 of 3 Introduction This last installment of Beyond Megapixels contains an overview of camera function, such as metering, white balance and focusing systems, popular filetypes and their usefulness to the photographer, and features that define each digital camera. In keeping with the editorial nature of this series, I will share my preferences and opinions of these aspects when I deem prudent. Function The average photographer will be relying on the automatic systems of the camera to provide the correct focus, metering and white balance when taking a picture. In difficult or tricky shooting situations, the photographer may choose to manually adjust these settings. Before delving into the specifics of these variables, it is important to first make certain that a camera has the ability to manually control these settings. When you are first purchasing your shiny new camera, you may not think that you'll ever venture beyond the automatic settings of the camera, but as you become more and more addicted to digital photography there is a great chance that you'll find yourself wanting more control over the shot. That said, let us move on to focusing systems! There are two major factors that characterize a good focusing system: speed and accuracy. It is difficult to test this when shopping for a camera as you are, at best, limited to the lighting situation in the store you are browsing at. A true test of a focusing system is in low-light, low-contrast environments. The Sony has a unique advantage in darkness with its utilization of a laser pattern "holographic" focusing system. The ability to choose a focus point within your viewfinder can assist you in focusing exactly where you want. The Minolta A2, for example, has five focus points to choose from, and the Canon Digital Rebel has seven. Particularly in situations where you will only have a shallow depth-of-field, focusing on the right spot is imperative, or you lose the shot.  The metering system of a camera determines the correct exposure when shooting in aperture priority, shutter priority, program and automatic modes. Even in manual mode, the metering system will tell you when your exposure is correct. The latest cameras sample from up to and over 1000 points of a scene and set the exposure accordingly. Various metering modes will change how much "weight" is given to an area of the scene. Center-weighted metering will factor the center of the scene more than the edges when metering the scene. To visualize exactly why this is important, envision a man in a black tuxedo with a snowy mountain-side in the background. If you expose for the bright white of the snow, you will lose the tuxedo into a deep, dark black pit. On the other hand, if you expose only for the black tux, the snow is likely to blow out completely. Okay, so maybe you won't have to deal with the tux on a mountain-side, but a wedding dress is just as bad.  You may have noticed that sometimes when shooting under fluorescent lights, your pictures come out very yellow. This is caused by poor automatic white balance. Digital cameras must adjust for the color temperature of lights when processing an image. Incandescent lighting casts a warm glow throughout a scene, and the camera adjusts colors accordingly so that everything is not affected by the color of the lighting, meaning that a white wall will appear white in the final image if white balance is done correctly. The ability to manually set a white balance is very useful when shooting in difficult lighting situations, such as a mixed light environment with both fluorescent and incandescent light sources. Before taking the shot, you can shoot a frame of something white or grey (there are tint-free cards made specifically for this purpose), and the camera will use that info to process images correctly. Just remember that a custom white balance is only good while shooting in the same lighting environment, if it changes, you need a new white balance. In general though, the automatic and preset white balances available in the latest prosumer and DSLR cameras are adequate. 
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