Urgent bounce flash question 760D owners

walkaround wrote:

WilbaW wrote:

walkaround wrote:

WilbaW wrote:

How do you explain this? - "If I flash exposure lock on the subject before snapping the bounce flash picture with the 70D, all the photos are exposed perfectly. If I don't FEL before snapping the photo, they are all very underexposed."

Because FEL uses an entirely different method of metering the subject.

It's metering the subject off the center zone, I hope everyone realizes that.

Which words say that, and what else do I need to know to interpret them that way?

"Aim the viewfinder center over the subject where you want to lock the flash exposure, then press the <*> button."

Wow, you're not joking, are you? That is simply invalid logic.

"To make an FEL reading you bring a mid-tone subject area to the centre of the viewfinder and press either the exposure lock or flash exposure lock button (varies with camera)."

If FEL always used Evaluative, where would Canon want you to put the mid-tone subject area in the viewfinder?

Or to put it another way, if FEL doesn't change the metering mode (so if the flash is in Evaluative FEL will meter in Evaluative and if the flash is in Average FEL will meter in Average) - how would we have to revise the two instructions quoted above for them to make sense?

And if we look at the Troubleshooting section of the 430EX II manual, we see the very first point about underexposure mentions reflective objects. (also warns about HSS and range decrease)

Err... you think that the problems reported with the 70D are because they have a mirror in the shot?

Err... I'm explaining why using FEL gives a different result than not using it.

So what do reflective objects have to do with that? In the absence of reflective objects, why should FEL give a different result?

There are no "problems" reported that are unique to the 70D.

You are missing the point that this is a problem that is unique to some 70Ds. Generic underexposure with bounce just needs a bit of FEC. This problem with some 70Ds is drastic underexposure that is avoided by using FEL. Big difference.

The same "problems" were reported by 5D2 and 5D3 owners as well (among other models, as noted). You don't find that to have any bearing on this discussion?

I think your desire to defend the 70D is clouding your logic and judgement.

I can't explain (yet) why it seems to work differently in Rebels. They use E-TTL II also, and should behave the same, although they could be using a different algorithm and we would never know. It's entirely possible that, as an entry-level camera, it is making assumptions about flash output that are not deemed appropriate for the enthusiast and pro models.

Sure, but what evidence do we have that they do behave differently? What differences are observed?

Every thread has a common theme: "my Rebel took perfectly exposed bounce photos... my 5D2, 5D3, 6D, 1D2, 1D3, 50D, 60D, 70D shots are always underexposed, when using bounce flash (with a sto-fen... lightsphere... etc)."

That's not what I see, so until I see some evidence - like, here's a test that shows the Rebels behave differently - I'm going to continue assuming there isn't a fundamental difference.

I haven't specifically tested this lately, but in my experience you get similar brightness with or without FEL, in evaluative or CWA, with the flash is direct or bounced. Not "very underexposed" without FEL as reported for some 70Ds. That's not normal.

Do you see a single example photo in this thread, or any other on this topic?

Not in this thread but I've seen enough in the 7D forum to be convinced that some 70Ds have a problem that goes way beyond needing +2/3 or +1 FEC when bouncing, and goes away with FEL. The difference between normal and FEL shots is not explained by different metering modes.

Do you see detailed steps to reproduce?

Yes.

Why assume that your shooting conditions are representative of all use cases?

Not.

I don't see this "problem" either, but I'm bouncing in a normal sized white room, without modifiers, in Manual exposure mode, with a subject only a few feet away (usually).

Your 70D doesn't have this problem. That doesn't mean nobody does.