What is your most often used metering system..

Partial and spot look the best to me, with the nod going to spot.

What "spot" did you meter with and did you use the FEL function?

I picked those because the outside looks overexposed in the others. Also, the curtains show much more detail in the spot and partial shots.

The only "spot" there is on a 40D, the center spot.
No, I didn't use FEL, as that implies spot metering for the flash as well. I haven't recomposed anything, so spot metering the flash would meter out through the window. I wanted to show that the flash was metered using evaluative, in spite of the ambient being metered with different modes.

The curtain shows more detail in these images exposed according to partial and spot, since then the outside is exposed one stop less, and thus the ambient light doesn't shine through and wash out the texture of the curtain that much on these images. Flash exposure is best verified by looking at the window frame, since no outside light shine through that one.

Considering that a substantial part of the image consists of surfaces either illuminated by ambient light shining through (curtain) or being reflected inside the room (window frame), it's not unexpected that the outside is overexposed when using evaluative or average for the ambient light. Only spot is fully capable of separating the outdoor light from the indoor light.

apersson850 wrote in post #8144811
The only "spot" there is on a 40D, the center spot.

Let me rephrase . . . what item in the photo was your spot on for the metering? It's possible the spot caught the right edge of the white building but it appears to fall on the shrubs between the two buildings as that appears to be the center of the photo.

apersson850 wrote in post #8143950
Fair enough. Later I'll upload four images, taken with four different metering modes on the camera, without affecting flash exposure.

Still, what is it you saw that is contradictory above, so that I can fix it? I can't find it myself.

apersson850 wrote in post #8144586
All right, no further comment so I'll let the post above stand for now.

Sorry there, didn't realize I wasn't giving you enough attention. Essentially in reading your original post, you're saying that the cameras metering mode has no impact on the flash exposure, but then you say:

It seems contradictory to me. I guess maybe you mean by using FEL, but who knows.

Anyway, here's the bottom line. I'm not saying your wrong, but I can't find anything that says you're right, and you can't either. I reread my 580EXII manual, that doesn't seem to say anything about the metering mode your camera is in. It does mention external metering mode, and speaks of the meter on the flash, but that is different from ETTL, which I'm certain you're aware of. I looked through Canon articles, searched the web, etc. I can't find anything. I'll keep looking, because I'd love to know what the right answer is.

That's why I wrote:
Flash light will not be spot metered unless you specifically tell the camera to do that.

Which brings us into the next part, FEL (Flash Exposure Lock).

I'm sorry if that connection wasn't clear enough. I did refer to FEL when spot metering the flash, yes.

Regarding the question further above (Optiq), so yes, I aimed the center of the camera at the bushes to the right of the house. I deemed the house itself as too bright, but foilage is usually close to "normal reflection", so I hoped for that to give a reasonable exposure. I didn't want to mess with any exposure compensation here, to avoid confusing the matter any further.

Now returning to the search for other sources for this information. I do consider the images I posted as supportive of my claim, but still.

Here's a little about E-TTL flash metering, but unfortunately they don't specifically state if the metering setting on the camera has any effect.

According to Check Westfall, older Canon cameras seem to override the user's setting of metering method when the flash is turned on. Statements summarized here. My test suggests that they don't any more, since the exposure most definitely changed when changing metering mode.

At dpreview I found this thread, where someone who seems to have studied Canon's flash system thoroughly supports my claim, i.e. that ambient is measured with the selected method, flash by evaluative or average, as you set it. Note that they are discussing E-TTL, not E-TTL II.

I'll have to leave now, but if I find some more info, I'll come back.

apersson850 wrote in post #8143757
Unfortunately almost all of this post is incorrect.

Although flash metering is indeed done by the camera, flash metering method doesn't depend on the camera's metering method at all.
You can set the camera to evaluative, partial, spot (if it has it) or center-weighted. Regardless of which, you can still set the flash metering to evaluative or average.

Existing light is measured with the metering method selected for the camera. Depending upon the exposure mode selected, the result may be used at any rate from not at all to 100% to determine how the image is exposed.

The flash light is then measured using the pre-flash and the metering method selected for the flash. If that's evaluative, the camera tries to figure out the proper power ratio for the flash by using some "clever" math.
If a zone in the evaluative matrix has a large difference in brightness with and without flash, then it's either very close or very reflective. E-TTL II also reads back the focus distance of the lens, and if the flash is pointing forward, this gives the camera a hint about which power ratio you reasonably need to illuminate whatever you focused on.
If there isn't much difference before and during the pre-flash, then that part of the image is probably out of reach for the flash.

When using average flash metering, no such fancy tricks can be applied. The camera will meter the pre-flash and set something that gives a reasonable exposure, on the average.

But do note that this happens regardless of whether you set the camera to evaluative or spot or whatever! Flash light will not be spot metered unless you specifically tell the camera to do that.

Which brings us into the next part, FEL (Flash Exposure Lock). If you press the */FEL button (which depends upon your camera) when the flash is on, you'll trigger the pre-flash at that instant. Now the camera will indeed spot meter the flash (or use partial mode, if spot metering isn't supported by the camera in use) and lock that flash exposure for some time (16 s for several models). If you spot meter flash on a black suit, you'll most likely overexpose the flash light in that image, unless you turn down the FEC as well.

But this, once again, is independent upon the metering the camera uses for existing light. So you don't have to turn spot metering on to do this.
As long as FEL is active (hasn't timed out) it overrules the normal E-TTL metering, so when you actually take the picture, no pre-flash will emit. You did that manually when you engaged FEL.

When combining flash and ambient light in a scene, the camera will try to reduce exposure of both somewhat in order to avoid overexposing the sum of the illumination. But that takes that both camera and flash is in an automatic mode, of course.

hi anders, can you expound on the FEL stuff, i thought if i hit FEL and the flash in on evaluative, it will flash meter on evaluative when you hit the FEL button. Much of what you said was my initial thinking but i got a bit confused with the FEL part coz you said if your camera is on spot then it will spot flash meter.....

i do hope we get the definitive answer this is great learning stuff!!

I like to stay in evaluative - when needed, I will zoom in on the proper area and then use exposure lock to keep the correct exposure after recomposing. Kind of my round about way of spot metering.

ccp900 wrote in post #8145899
Hi anders, can you expand on the FEL stuff, i thought if I hit FEL and the flash is on evaluative, it will flash meter on evaluative when you hit the FEL button. Much of what you said was my initial thinking but I got a bit confused with the FEL part coz you said if your camera is on spot then it will spot flash meter.....

When using FEL, the camera will spot meter the flash, regardless of which metering mode the camera is set up for, and also regardless of which metering mode the flash is set to use.

That's why the manuals for camera and flash tell you to aim the center of the viewfinder towards the important part of the subject when you press FEL/*.
Here's from Canon's web site:

Reframing the image after locking the focus can sometimes dramatically alter the required exposure level. This problem can easily be eliminated, however, by using FE Lock to maintain the initial flash level. Similar in many ways to the AE Lock function, FE Lock uses spot (or partial) metering to determine the ideal flash level and fires the flash accordingly when the shutter button is pressed to ensure appropriate exposure of the subject even during reframing.

Link to the full page. The reason for why it may be spot or partial is that some cameras, like the 400D, doesn't have spot metering.
So you can have the camera on spot metering, or evaluative or whatever. When using FEL, the flash light will be spot metered anyway.

Reading more about E-TTL II vs. E-TTL, it seems that the exact behavior of light metering has changed over the years, and also depend upon which camera body you combine with a certain flash. No wonder we have several, sometimes contradictory, opinions about how it works.

The information is spread over many web sites, so it's difficult to link to it all, but basically it can be condensed to this:

For ambient light, when using a flash, camera bodies:

• Will force evaluative metering (E-TTL).
  
• Will force average metering (E-TTL).
  
• Will meter according to the mode selected by the user (E-TTL II and maybe some with E-TTL).

• Use evaluative metering, mainly at the active AF-point (E-TTL).
  
• Let you select evaluative or average (E-TTL/E-TTL II).
  
• If selected, use evaluative to find out parts of the image that are lit by flash, but not reflective like mirrors (E-TTL II).

I know that Chuck Westfall posts over at DWF, and I figured if anyone could say for sure it would be him. So I asked him whether the flash respects the camera's metering mode, and here's his response:

So that settles it, I was wrong and I'm happy to get this straightened out. It's unfortunate that the owners manual for the flash really doesn't offer any information on the metering modes.

Anders, sorry I don't think your test images are very conclusive--you're basically testing whether you'll get a proper exposure with both your camera and flash in automatic modes. Not very surprising that they all look well exposed.

Anyway, this puts the topic at rest for me, and I'm happy to leave my camera in spot metering mode for everything now.

This is really fantastic information, especially for those of us just starting to use speedlights. It goes to show that even seasoned photographers can be confused by the anemic information given in 'manuals'. This should be stickied for reference. Thank you Anders and Tim for finding out definitively what the answer is and for having a dialogue that benefits all of us.

Don't quite like camera metering but it's a lifesaver in changing conditions. That said I usually use evaluative or centre biased (whatever it's called).

IMO an accurate handheld light meter is the best though.

ClickClick wrote in post #8132426
Spot, Partial, Evaluative,, etc.. and why do you use this one?

centre weighted > coz i want to emphasize my subject but also considering the surroundings.

you can get away with centre weighted as well.

timnosenzo wrote in post #8148300
Anders, sorry I don't think your test images are very conclusive--you're basically testing whether you'll get a proper exposure with both your camera and flash in automatic modes. Not very surprising that they all look well exposed.

It doesn't matter now, when you are convinced by Chuck, but the idea with my test images was to see if different metering modes on the camera would change the exposure of the world outside the window, but leave the flash exposure inside unaltered.
Which is what happened.

I use Evaluative the vast majority of the time as I am not in a studio.

When I have better metering on the subject that I am working with I use spot. I have had great results with both.

-Eric-