E-TTL, active focus point, and compensation

I did a little experimenting today with the flash, and thought I'd share the results. While many here are already familiar with the "quirks" of E-TTL, there are quite a few here that might benefit from this.

Anyway, here it is:

Mr. Tan Hat and Miss White Door have decided to get married, and have invited Tom W as their photographer. So Tom, always eager to the task gathers up his 10D, appropriate lenses, 550EX flash, a few sets of batteries, and assorted other equipment and heads off to take some wedding photos.

In the first photo, the active focus point is centered right over Mr. Tan Hat's tan hat. This provides a satisfactory, balanced exposure with some detail showing in both Mr. Tan Hat's dark jacket and Miss White Door's white dress.

As long as you got paid, that's alright

Interesting example

Why Mr Tan Hat gave me the coat off his back.

Good example. You better write a "how-to" book.

---Bob Gross---

Tom, it looks like from those results that unless we are dumb enough to put the active focus point over a pure white or a pure black, we'll probably land on our feet when using E-TTL2 (especially if shooting RAW).

I wonder what would have happened if you used bounce flash instead? Maybe the happy couple will need some honeymoon photos.

Thanks.

Mike H

Well, if II is as good as promised, you should be able to compose the picture as you wish without worrying about extreme dark or light subject material. And sometimes, in order to get the composition you want, the active focus point unfortunately does fall over the bride's dress or veil, or the groom's navy tux (or the black Mercedes in the garage or whatever).

I shot these RAW, but didn't do anything to them in the conversion - they're pretty much straight out of the camera.

Bounce flash would have brought similar results (without the shadow of Mr. Tan Hat's hat, of course). E-TTL meters on the reflected light of the pre-flash, and will automatically adjust output to compensate for bounce, or diffusers and such, so that the same amount of light will hit the target.

I've shot a few with bounce on this flash, but this was adequate to illustrate the effects of dark and light subjects and the necessary FEC that helps overcome these effects.

If I get a chance after dinner this evening, I may fiddle around a little more with bounce. The 550 is new for me, but it does resemble my 380EX enough that it has been pretty easy for me to adjust to.

Thanks for the response.

I'm not so sure about bounce giving you the same results, since this new system is working distance into the equation, something that is complicated by the use of bounce flash. I will have to convince myself that you're right with some tests.

You would likely get different results if custom function 14 were set to average exposure over the entire AF elipse (page 151 of the manual), rather than evaluative metering. Several users on another board report better results when setting the flash metering to the averaging pattern. In your sample photos, my guess is that it would work better (since it would average the blacks and whites). It would be critical for wedding shooters to know which pattern works better.

I'm planning to do some tests when my neighbors come back into town in a few days. They're such good sports.

Mike H

Mike H wrote:
Thanks for the response.

I'm not so sure about bounce giving you the same results, since this new system is working distance into the equation, something that is complicated by the use of bounce flash. I will have to convince myself that you're right with some tests.

You would likely get different results if custom function 14 were set to average exposure over the entire AF elipse (page 151 of the manual), rather than evaluative metering. Several users on another board report better results when setting the flash metering to the averaging pattern. In your sample photos, my guess is that it would work better (since it would average the blacks and whites). It would be critical for wedding shooters to know which pattern works better.

I'm planning to do some tests when my neighbors come back into town in a few days. They're such good sports.

Mike H

I apologize, Mike - I probably should have noted that I'm shooting with the 10D. All I have is "regular" E-TTL, not the newer version. Which is why bounce flash really won't change the exposure in my case.

Given that you have E-TTL II, I would think that your results will be more consistent, especially if you have an average exposure option for tough situations.

I am looking forward to seeing how the newer E-TTL II does in a similar situation, especially since I am of the mind that Canon will include it in the next consumer grade digital SLR, just as they've included it in the Elan 7N. Unless I suddenly change professions (and start making money with cameras), I'm not likely to splurge on the 1D Mk II any time soon, even if I crave it.

Tom, no need to apologize. I didn't read your original post carefully enough; you did say that you were using the 10D.

If it makes you feel any better about not getting a Mark II, it's heavy, expensive, and much more complicated to use than the 10D. I'm going to need a lot more time to learn this camera than the 10D. That's one of the downsides of having a ton of features.

Mike H

thanks for this very instructive example tom. as you said, there are a lot of people who will take great advantage of this post (myself included). but that makes me need to learn more about how to correctly read pictures histogram since that was how you guessed that the picture was over or under exposed. is it about how homogenous the histogram is? moreover, how do you know that the shot is over or under exposed (I mean for more complicated picture composition).
please feel free to giave some documentation references for better understanding histograms
regards

Khalid

Very helpfull post!

Thanks Tom!

Edited with histograms

Khalid, sometimes, you don't even need to look at the histogram to see if a shot is going to be way over- or under-exposed. The overexposed highlights will flash on the LCD after the shot, and the underexposed will just look too dark. But the LCD isn't the best tool for looking at the actual image except for composition. Better to use it to view the histogram.

Anyway, I always keep my camera LCD set to show the histogram along with a small version of the image. Unfortunately, I don't know how to get the histogram image into a JPG so that I can post it here, or I could show you just what I was dealing with.

EDIT: With the help of PacAce, I was able to preserve and create copies of the histograms for each of the 5 shots so I will include them with the following text as needed. Pardon the nasty JPEG artifacts on these - they aren't to be viewed as artwork.

Anyway, I'll "borrow" this simple chart from the Luminous-Landscape web site:

Top contributer , top explanation
thanks a lot TOM

It would have been interesting to see the effect of CF 4-1, which remaps AF to the * button, on ETTL. On a 10D (and probably the 300D), ETTL is supposed to operate more like an averaging auto flash in this case.

Just going back to Custom Function 14 – Auto Reduction of Fill Flash
Can someone please explain the difference this makes and the possible situations you might use either option

Thanks