Understanding Histograms in Photography

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 sort of histogram to display if your image is correctly exposed.  DSLR’s mainly show a live histogram so you can adjust your settings whilst 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 understand 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.

  1. Blacks
  2. Shadows
  3. Midtones
  4. Highlights
  5. Whites

The key to getting a good exposure is keep everything near the midtones as best as possible.  More importantly, any information that is more to the left (blacks) or to 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.

histogram,photography

An example of a histogram. A good method is to get the exposure mostly in the middle of the histogram unless you intentionally want to underexpose or overexpose. Too much information information on the far left or right risks loss of exposure which may be unrecoverable.

The histogram is taken from the below image.  Whilst it falls more towards the blacks and shadows, the midtones are just right to give this image a good exposure.

exposure

Image used from the histogram above. It shows no over exposure or no excessive blacks.

Over Exposure & Under Exposure

As an example, i will use Photoshop to overexpose & underexpose the image above to show how the histogram moves.

histogram,overexposure

Example of overexposure. If this was taken through a camera then most of the information on the right would be lost. The highlight clipping warning light has also changed from black to blue. It can be worked on through editing, but the finish would not look like how it normally would if exposed properly in the first place.

histogram,underexposure

Example of an underexposed image. The shadows are too dark for the exposure. The shadow clipping warning has also changed colour. Again as above, some work would be needed to recover this and it may not look right.

Does it Work Everytime?

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 dark’s due to the sky.  When underexposing or overexposing is intentional then leave it as it is.

Final Words

This is just a short explanation of using histograms.  The are useful things to use but should not 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.

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