Evaluative vs Average.

[tecboy]

Has anyone tried switching ttl mode? I find the average makes the subject brighter.

 

[weepete]

I've not tried it but it would make sense given the way CWA metering works.

 

[Derrel]

There are a lot of variables that can come into play on TTL flash metering and control. Brand of camera, specific modes, what flash is attached,focus point in use, focusing mode, what general focal lengths are being shot, distances involved, venue,and more. For example, in Nikon, there is TTL and TTL-BL, for "balanced lighting", which is often used for slow exposure + flash shots, like say outdoors as the sun sets...or indoors with slow speeds when one is doing what's called dragging the shutter. Not "all" flashes offer "all the camera-maker" modes either!!!!

Some ways to get a feel for how the flash is evaluating and metering the output:

With wide-angle shots, where there is a lot of background, and the flash is told to make an "evaluative" reading, you'll probably find that the background is bringing the amount of flash down, lower, lower flash output, in many cases.

Try a tightly-framed flash-lighted headshot made at a telephoto lens setting, and compared the results in evaluative and average metering. Zoom back to a shorter and shorter lens lengths, and in the process of that, picking up more background, and compare the results. Maybe also try the same thing using a wide-to-normal zoom, like a 17-50 on APS-C, and see how your flash,and your camera, reacts.

Also: test to see if the Evaluative has any type of "change-over" zone: shoot a series going from fastest synch speed, and down to 1/8 second, and see if at one of the slow speeds, if there's a difference in the amount of flash to ambient ratio. Make SURE to allow the flash time to fully recycle between shots!