E-TTL Metering with 550EX and EOS bodies

[alex_tudor]

I've read posts and Guy's FAQ at photonotes.org, but I'm still

confused and unclear at something that perhaps should be clear but

I'm just missing it.

 

From the FAQ:

 

"E-TTL flash metering patterns:

 

The camera uses its evaluative metering system to meter the flash

output, based upon the preflash. When in autofocus mode most EOS

bodies bias flash metering toward the currently selected AF point,

but always in an evaluative mode pattern - they don�t use spot or

partial metering patterns. When in manual focus mode it appears that

at least some EOS bodies switch to centre-weighted averaging.

 

Note, however, that this biasing of E-TTL metering to the active

point is potentially problematic, since it means that the flash

metering is done in almost a spot-metering fashion. Many user

complaints regarding flash metering problems in E-TTL mode appear to

be linked to this issue. If the camera happens to be over a dark

object, for example, flash metering can be considerably overexposed,

and vice-versa. The standard answer to this problem is to use FEL

and meter off something mid-toned, but this is clearly not a

solution for rapid-shooting situations such as weddings and sports.

Another approach is to set the camera lens to manual focus, since

the body apparently switches to centre-weighted average metering in

that mode, but that�s obviously not a useful answer much of the time

either."

 

A question I have is what IS the solution really? And secondly, when

I choose a metering mode (whether in Av or M mode) on my camera is

that ONLY for ambient/background metering? Is that completely

separate from E-TTL's metering which is tied to the focus point as

mentioned above?

 

Alex

[alex_tudor]

I should add that MY solution is to be in M or Av mode in spot meter mode tied to 11 AF points. No FEL no recompose. I just move the AF point around until I find an even tone to meter from.

 

But I still don't understand how the regular metering interacts with E-TTL's metering as I asked above.

 

Alex

[bill_goldman]

First of all, I'll try to answer your questions step by step, taking your thread from the top. Your first paragraph is essentially correct except that when you turn your flash on (in E-TTL mode), it uses the evaluative metering system to read both ambient and flash regardless of the mode set on the camera. Flash exposure is biased on the area covered by the focusing point(s) achieving focus. I am sure you are aware that you should not recompose as the focusing point will move from your selected area to another, perhaps inappropriate one.

 

I'm not sure about some EOS models reverting to CWA metering in manual focus mode. I know my EOS-1v defaults to the center focusing point in manual focus mode and apparently still uses evaluative metering.

 

In your second paragraph you state that the flash metering is akin to a spot meter reading. This is not true except for FEL. Normally flash exposures are biased towards the active focusing point(s) but the area around the affected metering zone is also evaluated, but weighted less and finally the remaining zones are evaluated. This is basically the same way the evaluative system works for ambient measurements.

 

The algorithms for the E-TTL system vary somewhat for different EOS models. Apparently, the D30 and D60 were excessively heavily weighted on the active focusing point and proved troublesome for many owners. This has apparently been corrected on the 10D.

 

I think I have already answered the question you asked in your final paragaph but I'll restate it. The E-TTL flash system always uses the evaluative metering system for both ambient and flash metering regardless of the mode selected on the camera. That's why it's called E-TTL.

 

My answers to your questions are based upon a lot of reading of Canon literature (such as "Flash Works") and other sources as well as experimentation with my own camera and 550EX Speedlites. That's no guarantee that everything I said is absolutely accurate but I believe it is.

[alex_tudor]

Bill,

 

The paragraphs are from Guy's FAQ and in quotes. My question was answered by you: "The E-TTL flash system always uses the evaluative metering system for both ambient and flash metering regardless of the mode selected on the camera. "

 

That's what I wanted to confirm. I also have the 1v. I don't use FEL and recompose as I was saying. I frame, select from one of 11 AF points that I put on an even tone/place in the scene", and then shoot.

 

Obviously this is not the fastest solution as I have to move around fast to get to the right focus point, and for non-static subjects it's challenging since I may have to start over and reframe, re autofocus, shoot if they move out of my frame.

 

I'm trying now to see what is fastest and most efficient. I could try using the center AF point, FEL and recomposing, but I wonder if that's faster as well. Just a different method really.

 

What do most seasoned flash photographer who cover events, weddings, etc. do? What methods are most efficient. I realize there is no ONE method, and it comes from personal experience, but I ask anyway to solicit and inquire.

 

Alex

[jon_austin]

I "only" have a 420EX flash unit for my 10D, but I'd like very much to read input from experienced event photographers, as well.

 

The 10D only has 7 AF points, so fewer to scroll through, but still it's either that or place active AF point over appropriate subject, FEL, recompose and shoot. Seems there ought to be a better (faster) way...

 

Or are we all just making this too complicated? Maybe for flash shots, I should just switch to P mode, auto AF, compose and shoot?

[bill_goldman]

Alex, my procedure with E-TTL flash is to use the camera's 45 focusing point auto select mode. Since multiple focusing points usually achieve focus, that helps to average the exposure. I generally aim the center of the frame on my subject(s) and the camera usually grabs the main subject in the frame. If not, I recompose slightly and then it usually ends up where I want.

 

This is a no-brainer and it seems to work great for me.

[alex_tudor]

Jon,

 

P mode is easy, but you don't have control over aperture - DOF, shutter speeds, etc. No creative control. Also no control on how much ambient light you want to expose.

 

Indoors I'm always in M mode at 1/30 for static, 1/60 if I want to freeze, or 1/15 if I want implied movement. I use 400 speed film to get more light in the background. 800 would be even better and offer a better balance between the subject (which is lit/exposed by the flash) and the background (which is exposed how by my settings).

 

If there is enough ambient light indoors to get 1/30 for shutter speeds at f/8 or so, I use that which means I'm in fill flash mode which is nice for balance.

 

Alex

[alex_tudor]

Bill,

 

That does make sense but then I would have to change my custom function 13 to go back to 45 AF points from 11 linked to spot. The problem is that when I don't use flash I use 11 linked to spot a lot. So I'd have to keep changing that custom function.

 

Also if my subjects are not in the center, as they aren't many times, I would need to FEL and recompose anyway.

 

There MUST be easy methods. What do wedding photographers do with Canon equipment for speed? I could post this in another forum but this is an EOS question really.

 

Alex

[bill_goldman]

Alex, a lot of people poo-poo the idea of using Program mode. I know it doesn't give you control of DOF but with E-TTL flash, it does try to balance the ambient/background illumination with the flash-lit main subject.

 

I also know that many prefer to use Manual mode in order to have better control of DOF but I get the impression that they are not mindful of background exposure.

 

At first, I thought you were just over-analyzing the E-TTL thing but I see that you really have specific ideas of what you want to achieve and it's clear you have a handle on what you are doing.

[bill_goldman]

Alex, you're confusing two things. When you select 11 points with spot metering linked to the active focusing point, that only affects the MANUALLY SELECTABLE number of focusing points. All 45 points are still active in the auto select mode. In fact, I have the same setting on my camera.

[jon_austin]

Alex: I agree with you about the limits of P-mode, but I'm just wondering (like you are) if there's a better way to get really good flash results quickly.

 

Bill's one of the contributors here who's opinions I really respect, and maybe if our cameras had 45 AF points like his (rather than your 11 and my 7), this would be a non-issue.

 

Thanks for sharing your manual settings with me. I'll make up a cheat sheet from them to stick in my bag (I keep several of these crib notes with my camera; I don't shoot enough to have all this stuff memorized yet), and start experimenting to see what works for me.

 

Hopefully, we'll hear from other experienced photogs with equipment more like ours who will share their techniques.

[Ken Katz]

If your not shooting slides, I don't think you need to be all that fussy on exact placement of your active focus sensor on or near your main subject. I generally just try to avoid underexposure (getting the AF sensor over very light toned subjects like white walls), and get good exposure results. Print film tolerates overexposure so I worry much less about that. I get similar ETTL exposure results from the 45 sensor/21 zone meter EOS 3 and the 3 sensor / 6 zone meter Elan II. Shooting flash with a D60 is another story altogether.

[jon_austin]

Kenneth: I may be missing something, but while your approach does seem to address exposure, there's still the issue of (auto)focus: the camera's going to focus on the active/selected AF point(s), as well as use it(them) for exposure metering. Since recomposing after focus doesn't work well with E-TTL flash metering, this brings back the original issue of how many steps it takes to get both good exposure AND accurate focus. Maybe evaluative metering combined with manual focus is another way to go?

[alex_tudor]

Bill,

 

Yes - got that about the 45 and 11. I keep forgeting since I never use the 45 that I can scroll until it goes to 45! I'll try the method you mention and for things that are not centered, I will use MF which will make E-TTL meter (evaluatively) off the center AF point. Hopefully these two options will have me covered for flash.

 

Thanks for clearing up things. Sometimes the "simplest" things escape me.

 

Alex

[jim_simon3]

Alex,

Reading whole thread, I kept wondering if the white dresses were causing problems with the exposure. Does your experience turn up a graying problem or poor skin tones when you use the flash in E-TTL. There is a custom function on the 550 for non-E-Ttl that I've never tried. Maybe that will permit you to choose different exposure modes as it would be off the film metering. I can really see your problem as every picture is a different exposure and distance and as good as evaluative metering is, gettig different percentages of white dress, skin and others in the frame may create unacceptable results. Maybe someone else on the forum has experience with the custom feature for non-E-TTL

[bill_goldman]

Alex;

 

Here's another trick to speed up selection of a focusing point. Are you making use of the Assist button (to the left of the AE lock button)?

 

In the default mode, the Assist button sets the center focusing point. However, you can have the camera memorize any focusing point for instant recall.

 

It may not be obvious from the manual, but you can instead have the camera memorize the 45 point auto select mode as the Home Position. That way you don't have to cycle through the 11 focusing points to get to the 45-point mode. It's the closest thing to being able to toggle between a single focusing point and the 45-point mode.

[alex_tudor]

Bill - good tip. I didn't think of that.

 

Jim,

 

That custom function will make turn it into TTL. But TTL has the major disadvantage w/ off the film metering when using different film types. Films vary in darkness and obviously when you reflect light off something, the degree of reflectivity makes a difference. So this can create unexpected results when switching films, etc. I did look at this but it has more limitations and E-TTL than gains.

Of course with TTL you can recompose all you want w/o FEL.

 

To answer your question, I haven't had problems with whites or skin tones using E-TTL. As long as you meter of a focus point(s) that are medium toned for a nice 18%, you'll get great exposures. I think it does a great job. I just was looking to see how to make things quicker. How to more quickly choose the AF point. I'll try Bill's idea witht the automatic 45 point AF selection for centered subjects and for non-centered subjects I'm actually going to still use AF but with manual AF point selection. I was thinking of using MF but am afraid that metering off the center focusing point will not get great results at all times.

 

Alex

[whayne_padden]

Bill are you positive that when the flash is on, that even the background exposure is measured using evaluative irrespective of what metering pattern you are currently using? If that is the case it might make sense to meter for ambient light when the flash is off and use those settings in manual mode when the flash is on. This might help is you want to get a ambient reading without the subject involved.

 

Alex why do you need to find a mid tone, you can easily meter from a white subject for example and set +1 - +1.5 flash exposure compensation. Flash is no different to normal exposure, you can always correct the flash exposure if you know what tonality the subject you are metering from is

[alex_tudor]

Whayne,

 

Why a mid tone? Of course I can use exposure compensation but what's the difference really? That's more of a hit or miss. What if I don't have pure white to reflect back 9% so I can add +1? Finding something that will give me 18% back is actually easy. It's more about speed. I'm not even sure exp. compensation would be faster really.

 

I am curious about what you ask Bill, since that is essentially what I wanted to know as well.

 

Alex

[alex_tudor]

Typo - white reflects back 36% - black is 9%.

 

Also I'm not sure metering with the flash off, setting those settings in manual and then turning on the flash is really useful for fast situations. In fact it cannot be. That's why I always set my shutter to 1/30 (since that's my safe handheld slow shutter), 1/60 if I want to freeze motion, or less if I want to imply movement. The aperture is separate. I use 2.8, 4, 5.6 and max 8. And when I use f/8, I take off the OmniBounce, slide up the built in panel and ride off of that to light the background more. For 2.8-5.6 I use the Omni all the time with great results. 1/30 is enough for ambient light for me at those apertures. If I'm shooting 24mm I may go lower to 1/20 to get more light in. It depends.

 

BTW, for weddings and such events I use my 24-70mm f/2.8L and don't mess around to much with switching to other lenses. Outside I may use the 70-200mm f/2.8L for portraits (85mm, 105mm) with fill flash, but during the ceremony/event I don't have time to switch. And I use the 24-70 at 28, 35, 50, and 70. I treat it like 4 primes!

 

Alex

[whayne_padden]

Alex surely in some situations having to find a mid tone is more time consuming than just metering the subject and applying exposure correction. It's usually no harder knowing what correction to apply than it is choosing a mid tone. A white wedding dress would generally need +1.5 correction to keep detail in it (you would have done test shots before the wedding I assume). For that matter you can meter off your hand and you know that it's +1 compensation, beats having to find a mid tone, lock and recompose.

[alex_tudor]

Whayne,

 

What you say is true. But something I have to try to see. I know I can use my palm and add +2/3 or +1 stop of overexposure (this is not only for weddings so no guarantee of a white dress or walls either), use FEL, and recompose. I'll give it a try. I just don't see it being faster really, but perhaps because I have not used it. My palm would have to fall under the same lighting as the subject, I would need several additional steps to meter off my hand, lock, etc., which I can see as slowing me down. Perhaps not. But when I move around a lot doing that may slow me down. Sure it works. I will try it at a gathering next time to test it out along with the other methods and see what is fastest for me. Thanks. I'm just used to quickly finding a midtone instead of using exposure compensation a lot. Two different styles perhaps. I do use exposure compensation for landscapes of snow and such, but haven't when shooting fast.

 

One thing I may do to speed things up is limit myself to 9 AF points instead of 11. That way I can only use the wheel to navigate much more quickly around the 8 periphery points instead of using two wheels for H and V AF point selection. That is if Bill's 45 point method doesn't work or even in conjunction. I went back to look at my ES-E1 results to see what AF points I typically choose, and they are typically on the periphery or the center.

 

Alex