USING AUTO EXPOSURE EFFECTIVELY
By Lorraine Grula
Internet Video Gal
Auto exposure is convenient feature on a video camera that can be both good and bad. If you‘re not sure how auto exposure works, it can be hard to make your video look good.
Auto exposure averages everything within the frame and sets the exposure based on this average.
If the shot is evenly lit, this is A-OK.
However, if one section of your shot is either extremely dark or extremely light, using an average exposure can throw everything off and both extremes look bad.
These two pictures were taken within seconds of each other in the exact same lighting conditions. The shot on the left is dark, but not quite dark enough to be a quality silhouette. The view seen outside the window is terribly overexposed. Contrast that with the shot on the right. The lighting is much more even so the exposure looks much better. The small portion of the window you can see does not overwhelm the picture.
Since the bright window area is limited, the auto exposure knew NOT to expose for it. See what a difference it makes?
Here is a third shot taken seconds later, with the window cropped out completely. Most of the picture area is evenly lit so the exposure is virtually perfect and the room looks extremely bright. The small area of extreme brightness, (the side of the chest facing the window), is small enough for the auto exposure to ignore it. Who cares if that’s overexposed? It’s not very large or important.
Auto exposure works well in this instance.
MAKE A CHOICE
If you have manual override, expose your shot for whichever section is the most important. If it’s just a corner of your shot that’s too bright and you’re really trying to get a good picture of the building, let the sky be overexposed. However if the sky is what you’re going for, turn the exposure down and let the building appear dark.
If you do not have manual override, then crop out the part that’s too bright or too dark. The remaining section of your shot will then be reread and a new average will take effect. This new average will be more accurate for what’s remaining in your shot, just like the two examples above.
The bottom line is, for an auto exposure to work well, your shot must be evenly lit. Overly bright areas and overly dark areas should be avoided and the easiest way to do that is crop (cut) them out.
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