Originally Posted by mtimber
I am failing to understand why I would need to use EC?
I always shoot in manual and in RAW, so maybe I don't need to.
Could someone explain why I might need to use Exposure Compensation?
Five page of replies and no one really has given you the reason why you do not simply always expose per the meter
Let me explain, first by making two fundamental metering principles highly visible to everyone...
- First principle: All reflected light meters assume that the area which is metered is either solely 18% gray in tonality, or that the range of brightness encompassed by the area of the metering will all average to 18% tonality ('mid-tone' average)
- Second principle: If the target area (or the full area which is metered) is brighter than 18%, your photo will be UNDERexposed if you simply follow what is indicated by the meter. And if the target area (or the full area which is metered) is darker than 18%, your photo will be OVERexposed if you simply follow what is indicated by the meter.
Now let us apply the two principles to the use of EC (or Manual mode metering's placement of the 'needle' to one side or other, not centered
on the scale). But first let me state that I am NOT talking about 'Exposure Compensation' the camera feature, but about 'Exposure Compensation' the photographic technique of not simply 'following the meter':
Because of principle #1 and #2, you must employ a 'fudge factor' to bias the meter reading back to 'proper exposure'. The amount of fudge factor can often be estimated; but, sometimes it is more difficult to estimate the fudge factor!:
- If you metered a bright target with a spot meter, and you then metered a gray card, so that you discover the bright area is +1.7EV brighter than the 18% gray card, it is very simple to determine that you use -1.7EV of EC while using P or Av or Tv.
- If you metered a bright target with a spot meter, and you then metered a gray card, so that you discover the bright area is 11.7EV darker than the 18% gray card, it is very simple to put the needle to the left of center by +1.7EV while using Manual mode exposure indicator in the viewfinder
- But if you are using Evaulative metering, because it is making multiple readings at various locations within the entire frame and you do not know how the metering is biasing the readings in importance (not a simple average!), it is virtually impossible 'to simply know' just how much EC to dial in (or how much to either side of center to place the 'needle' of the Manual mode exposure indicator).
You have to use the photographic equivalent of 'Kentucky windage' in shooting in situations, but it is tricky to do so with the meter in Evaluative! A practiced eye and lots of experience will often allow experienced photographers to have good estimates of the amount of EC to use (or how much to the right or left of center to place the 'needle' in the exposure indicator scale seen in the viewfinder during Manual camera mode. But using such Kentucky windage is far more unreasonable in a mode which is unpredictable; it is far less reasonable to do with an inherently unpredictable mode like Evaluative. Using EC with Evaluative metering is a bit like trying to shoot a rifle a long distance when the wind is gusty and inconsistent in speed...it is difficult to estimate how much or how little compensation to use because you have no idea just how Evaluative is biasing the zones!