Urgent bounce flash question 760D owners

snofox wrote:

It sounds like you are trying to use ETTL with a bounced flash. I am not an expert, but from what I have read, ETTLII only works if the flash head is facing directly forward.

No, it usually works great in all sorts of non-straight-ahead scenarios, but evaluative metering does some tricks that can make it harder to get what you want.

Once you tilt it up, there is no reliable measure of the distance from the flash to the subject and faulty exposure results.

AFAIK, the distance from the flash to the subject is irrelevant as long as the subject is in "range" (the flash has enough output to illuminate the subject). The distance from the camera to the subject (as measured by the lens) is used, apparently.

And if you modify the flash too, you lose even more light. Am I right?

You do, but E-TTL works by measuring how much light gets back to the camera from the subject. It doesn't matter how far apart they flash and subject are, or how much light you lose, it only matters that the flash can provide enough. In theory.

Apparently the 70D has this bounce flash "problem" that you describe, or some copies of it do. But I have never been able to understand why it should work with ETTL.

Low-powered pre-flash illuminates the subject, metering system detects that illumination, metering system determines the required flash output based on how much of the pre-flash made it back from the subject, metering system tells the flash to fire hard enough, flash fires that hard when the shutter is open. What could go wrong?

EDIT: Of course, the fact that lots of shooters claim that they can bounce the flash with ETTL successfully every time with some cameras seems to confound the issue, and it sure as hell confuses me!

The first thing you have to ask is what metering modes they are using. Canon defaults everything to evaluative, which is designed to do it all for people who don't want or need to take control. If you are trying to take control, eval. modes with get in your way and mess you up. My motto is, if it's compulsory in the Basic Zone modes, avoid it in the Creative Zone modes, so I use centre-weighted (ambient) and average (flash) and don't have any trouble. I haven't tried a 70D but I do believe there are some misbehaving ones.