Sunday, 2 September 2012

What is a Good Exposure?

The question what is a good exposure can be tricky, a good exposure may be one that is technically correct or one that the photographer feels right for the scene. 

Photo By Francois de Halleux

In order to render a good exposure, the subject or scene being shot should have certain characteristics.

  1. The subject / scene should have a full range of tones as opposed to ones which are mostly composed of either black or white.
  2. The dynamic range of the subject / scene should be within the acceptable limits of the camera being used.

If the subject / scene being shot satisfies both the above conditions then one could say a good exposure is one in which there is detail both in the brightest highlights and darkest shadows. For a medium contrast scene, the histogram should show an even distribution of tones and no sudden peaks or shallows.

How to achieve good exposure?

The best method of getting good exposures is to learn how to get your exposure technically correct. Once you have captured a technically correct exposure, you could then fine tune your image to suit the scene / your shooting style / taste.

A point to remember while fine tuning your technically correct exposure is that it is safe to adjust upto a couple of stops for scenes that have a dynamic range that falls well within your camera’s dynamic range. But if that is not the case, meaning the dynamic range of the scene is just within limits, then over exposing or underexposing will result in clipped highlights and shadows. 

When intentionally tweaking your exposure, it is recommended to do it by changing shutter speed values whenever possible as changing aperture values would also affect the depth of field of the image.

It also pays to have a good understanding of your shooting medium. so if you are unsure about the results you are getting by looking at the preview image and histogram you could take calculated risks.

  • When shooting digital it is better to have a underexposed shot rather than having an overexposed shot. As you have the option to bring up shadow details in post processing, especially if you are shooting RAW. But have no option to bring back details from blown out highlights.
  • When shooting film, it is better to overexpose rather than underexpose as there will be no details recorded in the shadow regions of an underexposed film.
  • If you are shooting transparencies you have very little margin for error so it will be better to take bracketed exposures of all important shots.

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