Exposure Mysteries

Why is exposure changing from image to image

when I’ve made no settings changes???

Have you ever made two successive images

  • without changing camera settings &
  • with no change in the lighting
  • AND then
  • discovered that they were not exposed the same
  • sometimes off by a stop or more?

This problem is common and usually stems from two main sources.

  1. Your viewfinder is exposed
  2. Auto-exposure-bracketing (AEB) is turned on

Viewfinder Exposed
If your viewfinder isn’t covered (with your eye, or something) light will enter your camera through the viewfinder and confuse the metering system (unless you’re using manual exposure).

The degree to which this affects your exposure depends on the strength & direction of the light

If the source is the sun, and it’s at your back – your image will be severely underexposed as the meter sees more light (due to viewfinder “leakage”) than is actually visible through the lens.

If the light is soft, subdued & omnidirectional you may not notice much difference

The resulting problem, if there, is always under exposure

Try it, it’s a simple experiment to perform

A time that this commonly happens is when a remote shutter release is used.

In this case, the photographer often isn’t looking through the viewfinder – and it’s exposed

The solution is simple. Cover the viewfinder with something, anything.

Some cameras come with a cover or mechanism for this purpose

I just take off my hat & hang it over the camera back

Imagine you just finished taking some bracketed exposures for use with HDR software – maybe 5 exposures from -2 to +2 EV in one stop increments.

After that you move on to another subject & maybe another time – without remembering to turn off AEB.

The problem is obvious – every successive shot past that point will be made at a different exposure setting

You didn’t make the exposure setting change

But the camera did and the result is the same – wrong exposure (or at least 4 times out of 5 ;-))

Again, the solution is simple – turn off AEB.

Here’s the hard part – realizing that AEB is on.

This is a setting, like increased ISO, that is easy to change & then forget.

Tomorrow I’ll discuss the topic of “mis-set” settings in general & how to avoid them. [Update – here’s that next post.]

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0 thoughts on “Exposure Mysteries”

  1. Thanks Ed for this information. I never thought about light entering the camera from the view finder. And I am certainley guilty of forgetting to change my settings.

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