Tuesday, 4 September 2012

What is Underexposure in Photography?

In the previous articles we discussed What is a Good Exposure? and What is Overexposure in Photography? now let us see What is Underexposure in Photography?

Photo By Sinu S Kumar

Underexposure happens when the amount of light entering the camera is less than what is required to make a good exposure. It may be due to a number of reasons like;

  1. The shutter speed used was too short
  2. The aperture used was too small
  3. Wrong selection of ISO

Digital photographers should know that digital cameras are built with a bias towards underexposure  for its automatic modes. Meaning if the built in light meter in a digital camera make an error in judging an exposure, it will choose underexposing rather than overexposing. This is done to avoid the unrecoverable problems that could arise due to overexposure.

The main characteristic of an underexposed image is the presence of dark areas with little or no shadow detail. Such areas which appears completely black with not much detail is called ‘blocked up’. 

Underexposed Digital Images

When compared to an overexposed image an underexposed digital image could be recovered to bring out the details in the shadows during post production. This is especially true if the image was shot in RAW format. However grossly underexposed images tend to suffer from banding and noise when being worked with as there is simply not enough data for the program to process.

Underexposed Film Negatives

Unlike underexposed digital images, underexposed negative film could not be recovered much. Underexposed negatives will only produce dark, lifeless prints which has no details in its shadow areas. If you look at the underexposed negative film carefully you will be able to see faint details in the shadow regions - if some information is actually present there. In such cases where there are faint details present in the negative film, it may be possible to enhance these using chemical intensifiers. Sadly most powerful intensifiers are now considered as harmful chemical and so are either uncommon or unavailable. But in case of important images well it might be your only option.

When shooting with transparencies you have no way to rectify exposure errors so either nail your exposure right or take bracketed shots.

Underexposure is not always a bad thing to happen, photographers often intentionally underexpose their shots to increase colour saturation, add an element of mystery to their shots or to create mood or bring about a feel by creative use of shadows.