If you rely on your camera's automatic exposure metering, manual exposure compensation can offer you some level of control over the outcome of this highly obscure process. In general, it allows you to override the standard behaviour of your camera which is designed to be good enough for most of the time – but is rarely ideal for the situation at hand.
Cameras enabled with exposure compensation will provide a dedicated control for its configuration, normally situated on their top panel. Looking as a round dial, or wheel, it will allow to add or subtract the specified exposure value to or from that calculated automatically by the camera.
Most cameras will offer manual compensation on the scale from -2 to +2 EV, sometimes from -3 to +3 EV, in ½ or ⅓ EV steps. Negative compensation values result in lower overall exposure, darkening the image and mitigating blown highlights. Positive values, on the other hand, cause higher exposure, lightening the image and highlighting impenetrable shadows.
As mentioned in the discussion of different metering modes, I strongly recommend using some variety of average metering for your landscape images. Chances are, your camera will offer centre-weighted, or integral as it is sometimes called, metering.
This mode evaluates the light from a large area of the image, giving more significance to the values in the middle of the frame. For scenes with uniform lighting, it's often far superior to the default multi-zone metering. The latter's predefined evaluation points deliver rather random readings highly dependent on the exact framing.
In contrast, variants of average metering deliver consistent exposure values in unchanged lighting conditions. This makes it easy to compensate for camera shortcomings due to any reasons whatsoever, as the measurements stay constant as long as the lighting does.
You'll know you have to compensate
I normally underexpose by ½ EV no matter what.
In general, using manual compensation to underexpose is safer, as you can always push an underexposed image in postproduction to achieve a satisfying result. You won't be able to do the same with an overexposed image: detail in blown highlights is lost forever and beyond recovery.
If you don't want to leave anything to chance or don't have the time to experiment with several compensation values, use your camera's bracketing option. With this, the camera will take several images with different exposure values offset by a predefined amount. One of the images will be exposed according to the automatically calculated reference value. The other 2, 4 or 6 shots will be divided in two sequences of equally under- and overexposed images.
The total number of images in the sequence as well as the exposure difference between them can often be configured. With 7 images set apart by 1 EV, you can get a range of exposure values from -3 to +3 EV compared to the automatic exposure. This should give you enough room for possible mistakes of your camera. Just don't forget to set it on a tripod.
My XPan can produce sequences with 3 images offset by either ±½ EV or ±1 EV.
Take some images with manual exposure compensation or using exposure bracketing function of your camera. Get a feeling for automatic exposure calculated by the camera. Practise to decide on compensation value before pressing the shutter release.
Tags: #exposurecompensation #cameraexposure #photographylessons
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