does E-TTL-II really use distance data????

If canon E-TTL-II flash algorithms really used distance data why do I have to dial in 2 stops compensation when I have a white foreground and background?
In fact the system performs no better than normal TTL.
AND yes my kit does have the ability to whisper distance data between its components.
Does the nikon matrix-ii system do any better?

The distance data only augments the calculation. Of course it only works with direct flash, so if you're bouncing or using some diffusion device then it has to fall back on its evaluation of the light reflected by the pre-flash.

Canon's earlier ETTL used the focus point for flash calculation, but it was criticized in its results. E-TTL II is never linked to the active focusing point. In fact, that is one of the main differences between E-TTL II and the original version of E-TTL. Canon's later ETTL-II does use distance data, but it does that only to compare the flash return with other same-distance zones, to determine highly reflective surfaces which might falsely bias the flash metering.
ETTL II weights and averages the flash metering for the subject and all other objects at the same distance as the subject. Same-distance zones which differ greatly in brightness are given less weight since they are likely to be reflections from small, highly reflective, objects.

As for FEC, one must understand that the metering assumes the target is 18% reflectivity, and when the actual subject brightness is brighter than that, the use of FEC is not unusual, as it is your way to inform the meter to "give more exposure than you think, because the object is brighter than you assume".

Also, remember that the meter is trying to make everything 18% gray. White will by default be under exposed at least a stop and 1/2 probably more if it is really dominate.

And, just looking at images shot by associates using Nikon during a wedding shoot and shooting essentially the same venue with similar bounce etc. techniques, the images look similar to my Canon images. I'm sure there are subtle differences but I doubt that one would be declared better once all the peculiarities are understood and accounted for when using the system.

dmward wrote in post #14763443
And, just looking at images shot by associates using Nikon during a wedding shoot and shooting essentially the same venue with similar bounce etc. techniques, the images look similar to my Canon images. I'm sure there are subtle differences but I doubt that one would be declared better once all the peculiarities are understood and accounted for when using the system.

It would be interesting to know if those nikon users are constantly fiddling with the FEC dial.

The problem is this: if there is large areas of white in the foreground with a dark,but multi coloured subject taking up the central area, this white wont blow out even though it is closer to the flash, so dropping the exposure on the subject which has been focused on.

Hence dialling in FEC even though the distance ,aperture set and ISO is all the information the strobe needs to make it's calculation on output.

The canon system does seem any better than what we had 20years ago.

If I set all meter to centre weighted the results are the same.

And I know about 18%grey, if distance data was being used it would not matter what the albedo of the subject was if distance data is actually getting to the camera/flash.

john5189 wrote in post #14763715
The canon system does seem any better than what we had 20years ago.

Yes, I think that digital TTL (all forms of it, not just Canon's) are rather inferior to film TTL results...it comes with the territory of not being able to read the surface of the sensor like it could be done with film.

Maybe if the camera knew just how powerful (or weak) the preflash was (relative to max power from the flash), then distance data could be factored into the computation. But Canon already knows via ETTL(I) that linking flash output to the selected AF point was not the right way to go.

john5189 wrote in post #14763715
If I set all meter to centre weighted the results are the same.

Your camera's metering mode for AMBIENT LIGHT will not affect flash metering.

However, you have a few options with E-TTL. Buried in your camera's custom functions is the ability to switch from EVALUATIVE (default) to AVERAGE E-TTL flash metering. For indoor use, I find this mode more consistent and predictable.

Also you have the Flash Exposure Lock (*) button at your disposal to essentially spot meter your flash exposure. This button might be an alternative to cranking up the FEC when you encounter a big, white tablecloth.

Curtis N wrote in post #14763859
Also you have the Flash Exposure Lock (*) button at your disposal to essentially spot meter your flash exposure. This button might be an alternative to cranking up the FEC when you encounter a big, white tablecloth.

FEC. Do you know what's great about FEC? The fact that if you hold the * button down to maintain the settings, the image and histogram wont appear. So you can't see if these settings are OK. Isn't that clever?

Curtis N wrote in post #14763859
However, you have a few options with E-TTL. Buried in your camera's custom functions is the ability to switch from EVALUATIVE (default) to AVERAGE E-TTL flash metering. For indoor use, I find this mode more consistent and predictable.

What I meant by this is
take an ambient light exposure the histogram shape is the same for Evaluative and Centre Weighted[NOTE no compensation and large white area in image]
then take a picture with Flash as only light source with either metering pattern and the histogram is identical to the ambient light histograms.

the flash output has been solely decided by the incamera light meter algorithm with no contribution for focus distance.

If you manual focus on near point or infinity the histogram is virtually the same too. I think the only difference is due to the image looking different due to the focus error.

I have tried this with a 5D2 and a 7D using a 580EX and a 580EX2

I wonder if the seperate colour meter sensor in the 1D series makes a difference?

I have worked out how to reveiw the image and hold the pre-flash reading

press the * , this tells the camera you want to keep the settings,and then press the pre flash button they have to be different buttons. The AElock and Preflash trigger have to be assigned to different buttons.
Then when you take the picture you need to hold down the * button when before and during shutter release. On release of the * button the image will display and the settings will be memorized. For the next shot you still need to hold the * button whilst you press the shutter release otherwise the subsequent shot will not use this info and you will have to start all over again.