Histograms – How to use it for Photography
Histograms are useful tools to determine how well an image is exposed. Most modern-day digital cameras have some histogram to display if your image is correctly presented. DSLR’s mainly show a live histogram so you can adjust your settings while composing a shot. Others will only show a histogram when previewing an image. It can be a little tricky trying to understand them at first, but once you know how it works, it is pretty easy to use them to shoot your image depending on what field of photography you are in.
Understanding the Histogram
There are five separate groups defined in the histogram. They will not be broken up for you when you see it, so you have to visualise where they are broken up.
The key to getting a good exposure is keep everything near the mid-tones as best as possible. More importantly, any information that is more to the left (blacks) or the right (whites) will risk a loss of exposure or information. This becomes more noticeable when editing or viewing on a larger screen rather than the camera screen.
The histogram is taken from the below image. While it falls more towards the blacks and shadows, the mid tones are right to give this image a proper exposure.
Over Exposure & Under Exposure
As an example, I will use Photoshop to overexpose & underexpose the image above to show how the histogram moves.
Does it Work Every Time?
Using this tool can help to get your exposure right. But it is not necessarily true when shooting particular scenes. When shooting high key images, you want the information to expose to the right more. The same can be said for underexposing. For example, a night scene will have lots of darks due to the sky. When underexposing or overexposing is intentional then leave it as it is.
This is just a short explanation of using histograms. They are useful things to use but should not be relied on all the time as it depends on the scene or situation you plan to shoot. It can help to improve your photography by understanding exposures for your subject.