Digital Photoguide

Part 5 - More on Exposure

December 2004 Magazine

Part Five of Digital Photoguide describes the effect of different exposures when taking a digital photograph and how to achieve correct exposure by using the Histogram. A set of examples showing a Class 180 unit in sunny conditions is reproduced here so that you can see the differences between them directly on a computer screen.

The first image shows four pictures of the same train taken in JPEG format at different exposures together with the histogram from the back of the camera. No manipulation has been done so that the different brightness and colour can be compared.

The key point being demonstrated here is that if you over-expose the original image you can’t manipulate it to match the results obtained from a correctly exposed image. Bright areas “burn out” and lose detail which cannot be restored. The second picture shows a section of the same picture after trying to adjust each one to give comparable brightness and colour.

The results of manipulating Pictures 1 and 3 are almost identical except that a small amount of detail has been lost from parts of Picture 1 due to over-exposure, as shown by the arrows.

Taking the picture using Raw format rather than JPEG could have helped here and the benefits of Raw will be demonstrated in a future Digital PhotoGuide.

Part Four

Part Six