EOS metering antiquated?

Started Mar 7, 2004 | Discussions thread
patrik_f
Regular MemberPosts: 418
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Re: Use AEL if recomposing after focusing
In reply to SFJP, Mar 10, 2004

I tested your theroy: The camera locks exposure at the same time as focus is locked. This means that if evalutive metering is used at that time, it will apply to the image as it looked when the shutter button was half-pressed (and focus obtained).

What does this mean? Well, it means that if you recompose so that areas with significantly different luminance are included they will not have been part of the exposure calculations. (One possible solution: Select a different AF-point that lets you not recompose. Time consuming though.)

In other words: All the intelligence in the evaluatve metering may be negated by recomposing.

BTW, I've also seen claims that the metering will be done on the recomposed image, but with the selected focus points. This would be even more nonsensical, and a simple test shows that exposure doesn't alter no matter what you point the camera at after focus lock has been obtained. (Servo focus is probably a different matter, of course.)

Regards

SFJP wrote:
The very point to understand is that the metering will consider in
priority the objects viewed close to the focus point in the viewer
at the time you shoot the picture. If you recompose after comosing,
it may not be at all the thing on which you locked the focus. So
the best way if using a center point focusing and then recomposing;
is to lock exposire by depressing the AEL button before
recomposing. You'll see then that your rate of correctly exposed
pictures will grow significantly.

patrik_f wrote:

Why is it that a fev very small highlights can lower the exposure
by several stops, still not being able to correctly expose those
highligths, wheras the sky, filling 25-30% of the viewfinder, is
allowed to be totally blown-out?

I feel less and less confident in the metering system. I might get
a light-meter and go back to automatic metering.

(The reason I complain at all has to do with the quick feedback a
DSLR can give. With film I wouldn't have thought so much about it.)

This is not an attack on Canon, as I admire the company. In
addition, I don't know if any other DSLR does any better.

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