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Avarege vs. evaluative flash ...could anyone explain to me how either of them works and what are the main differences ...thank You

drogos wrote in post #2886830
Avarege vs. evaluative flash ...could anyone explain to me how either of them works and what are the main differences ...thank You

In evaluative ETTL mode, the camera will determine where the subject is and calculates the correct exposure for the subject. If distance information is available from the lens, that will be entered into the calculation for exposure. Of course, this is just an over-simplication and there's really a lot more going on in the camera in evaluative mode.

In average mode, the camera simply averages the meter reading over the entire frame to determine exposure.

The best way to determine which option works best for you is to try each one and compare the results. You should try them in different scenarios because one might work better in one situation and the other in another.

Lukasz,

There is precious little official documentation from Canon regarding the differences between Evaluative and Average E-TTL flash metering.

Those who are accustomed to the less sophisticated flash metering technology from bygone days find the Average mode to be more consistent and predictable when flash is the predominant light source. You will still need to compensate for the luminance of the scene (-FEC for a black cat in a coal bin, +FEC for a polar bear on a snow bank).

When you're using fill flash outdoors, most people find Evaluative mode easier to use. When the background is more distant, the camera seems to do a better job of identifying the subject and accounting for ambient light when calculating the required flash power.

Like Leo says, experiment and see what works best for you.

Leo thx.... can i than make a very simplified statement that average would more likely lit the whole scene while evaluative cares more for a subject that is in focus ?? i;ve been using evaluative and i tend to get pretty dark backgrounds even though i use pretty high iso and low both time and aperture

drogos wrote in post #2887353
Leo thx.... can i than make a very simplified statement that average would more likely lit the whole scene while evaluative cares more for a subject that is in focus ?? i;ve been using evaluative and i tend to get pretty dark backgrounds even though i use pretty high iso and low both time and aperture

Yes, I guess it's safe to say that (for the most parts). But here's something to think about. When the background is better exposed, then your subject will probably be over exposed (slightly or by a lot, depending on how far the background is). Because of the way point light sources behave (the law of physics), you can't properly expose the subject and the background with the same flash unless the background is very close to the subject relative to the subject to flash distance. And adjusting the ISO will not have any effect on this phenomenon.

thx guys for your help..Leo ..i use bounce flash indoor 99% of the time ...well not exactly bounced since i put gary phong's modifier on ...so i would say 70% of the light that is heating the subject is bounced ... ettl can't make the right measurmement anyways ..av. or ev i have to constatntly work on compensation ..i guess i will do some test shots i post here so we can talk about it
thx again