| Digital SLR cameras are equipped with a very helpful tool to help you decide if the photo you took are correctly exposed. A feature borrowed from high-end image editing like Photoshop, histograms provide essential information such as highlights, midtones and shadows of each photo. A typical histogram of correctly exposed photo may look like 1b. |
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| An underexposed photo will have a lot of pixel information in the shadow area, as shown here in photo 2a. Conversely, an over-exposed photo will show a histogram that curve up on the highlights area, indicating too much "bright" pixels in the Photo 2b. |
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| However, not every photo will have a bell-shaped histogram to indicate that it's taken with correct exposure. A low key photo, for example might show a lot of pixel information in the shadow area, but does not mean it's underexposed due to the dark subject or environment such as photo 3a. A photo of bright subject, while correctly exposed, might reveal a histogram that might be mistaken for over exposure (3b). So remember: there's no one type of histogram for all photos. The one thing to always remember is to watch for unusual spikes at each end of the histogram diagram, which means you're losing details in these area of pure white or pure black pixels. |
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