by Mike McNamee Published 01/12/2013
Definition of 'correct' exposure is a rather difficult thing to pin down. This is in part technical and in part subjective. The technical bit lies in the camera's (or photographer's) decision on what to do when the dynamic range is greater than the camera can handle. The subjective side is the photographer's decision on how light or dark they prefer the scene - some like it lighter than others, some darker.
By way of explanation, consider the scene in which the sun is positioned behind an attractive cloud base but strong enough to cast really dark shadows. A very dark image will retain the cloud detail but leave the shadow devoid of detail. Conversely, an exposure to reveal the shadows will leave the clouds washed out. What is happening, then, is that the scene has more variation than the camera can deal with - the 'dynamic range' of the scene is greater than that of the camera. The problem does not just arise with clouds; the same is true of a bride with a detailed bodice to her white dress and her black-trousered husband (who, in truth, is almost always sacrificed; photographically that is, other views are held!).
This then is a classic dilemma and the photographer has to decide what strategy to use at the moment of exposure . The options for our imagined scene are:
1. Exposure for the clouds and abandon shadow detail.
2. Expose for the shadows and abandon the cloud detail.
3. Make a mid-range exposure, accept less than perfect shadows and highlights and pray you can recover the situation with your Raw file.
4. Make a series of images at different (bracketed) exposures and combine the best bits in Photoshop afterwards. This is the so-called High Dynamic Range technique and there are a number of ways of dealing with the post production.
5. For our over-lit bride there is another option - reduce the overall exposure but splash in a bit of flash to lift the shadows back into range. This is not an option for our landscape scenario.
Embarking on a series of exposures requires time and effort at both the image-making stage and in post production so it is as well to understand what you can actually get away with from a single exposure. This is where the Raw file comes into its own as it gives more leeway than a JPEG workflow.
Some scenarios are so time-short that a 'close enough' exposure has to do, eg from pitch side directly to the newsroom.
There are, however, some other considerations before you fire the shutter:
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