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| p.1 #3 · Correcting Clipping: How to? (noob question) |
Highlight clipping occurs when the exposure chosen by you or the camera's metering system is such that the brightness of certain regions of the scene is too great for the camera sensor to record.
Thus, the question of how to avoid this phenomenon is inextricably linked to the choice of exposure, which considers how best to represent the brightness of the objects in the scene. That is to say, you can certainly decrease the exposure in order to avoid highlight clipping (or eliminate it entirely), but the resulting exposure may be "too dark" for those objects in the scene you consider the most important.
When relying on the camera's metering system to determine exposure, the camera tries to take into consideration the relationship between the brightness of various elements in the scene to choose an exposure that avoids excessive clipping of highlights while presenting the primary subject with an average tonal distribution. Depending on the metering mode and the scene composition, the chosen exposure may or may not be your desired exposure.
If the exposure is clearly too bright and there is no risk of undesirably dark underexposure by decreasing it, then one can either shoot in manual exposure mode or use exposure compensation to decrease the exposure. This involves adjusting one of three possible settings:
1. Decrease the amount of time the shutter is open (i.e., increase shutter speed).
2. Decrease the lens aperture diameter (i.e., increase f-number).
3. Decrease the ISO sensitivity (i.e., make the ISO value smaller).
Each of the above adjustments affects the resulting image in a different way. For instance, doing (1) may cause objects that are moving during the exposure interval to appear "frozen" in time. Doing (2) will increase the depth of field. And doing (3) will decrease the amount of noise in the resulting image. And doing the opposite of the above has the opposite effect.
However, it must be stressed that the issue of highlight clipping really can only be addressed in the broader context of choosing the most appropriate exposure for the desired subject, which is one of the fundamental principles of photography. As one becomes more experienced with digital imaging, advanced techniques like HDR and exposure fusion may be used to address the limitations of the camera sensor's dynamic range when attempting to photograph scenes with an extremely large tonal distribution.