Page 31 - Learning How to Photograph with your DSLR Camera 2nd Edition Jan 2021

At this point, I would like to point out that the metering system in your camera assumes
the light reflected from all color and tones in the spectrum is 18% grey, which is the
middle tone. It does so that it has a standard when measuring the light coming through
the lens. There are two exceptions to this that can under or overexpose you image even
though it was metered correctly.

UNDEREXPOSURE can occur on metering an all-white subject. Recall that the
reflectance of your camera assumes every tone and color are reflected at 18% grey.
White on the other hand reflects twice as much light, approximately 36%. What this
means is the camera will measure that light at 18% and underexpose your image.

For example, I shot this photograph of a Great Egret on the left one morning and my first
shot was underexposed, even though I spot metered on the bird and the meter read
correctly.

I added 1 Stop of EC to brighten the image (moving the tick to the right with the
Command Dial while pressing the EC button on my Nikon). I rechecked my image on
playback to ensure the highlights were not clipped.

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