AE lock question in AV mode

Hi all, I have a question about AE lock in AV mode while using my external flash as a fill flash. I have read the book, and I am still a little confused. From my understanding, AE works as FE if your flash is on. So, if I want the camera to lock exposure for the background ( outdoors in AV mode ) then how would I do it. You see I don`t want my subject to be considered in the camera`s metering. SO my thought would be to pivot a little until my subject is out of the viewfinder, lock exposure for the background, pivot back and compose, take picture. I guess this workflow is not good simply because I have no AE lock function because my flash is on.

My reasoning for not wanting the subject in the viewfinder while the camera meters is simply because the bigger the difference between the subject and background, the bigger the camera will try and average it out, I want the camera to use the flash to compensate for the subjects exposure, and not change the exposure at all for the background. ( And I would still consider FEC down a bit - still have to experiment with that one )

Is this possible ? thanks a lot all

Set the camera to 'M'.

You could use CF 4-1
That way you use the * to focus and the shutter release button half depressed to lock exposure enabling you to focus/recompose.
You do loose FEL but you can still use the FEC like you say.

ooh Rene, M is a little scary, but maybe one day. I am dealing with children most of the time, so I need to be able to do what I need to do quickly, This is just family/hobby related stuff, not pro-stuff.

thx peatoire, I will check that out, but will the camera still fire a preflash and adjust the flash output as necessary, or do I lose that function completely ?

I have tried all this and the only way is manual. You have to be a bit predictive for your shooting situation (i.e. prepared) because if you try this, you, and I am sure you have, will find that you do not expose the rest of the frame properly if you get the flash the way you want.

The only way to out-smart the camera (and this is what you are trying to do), is manual mode.

Curtis will back this up and has all the Flash education info. Check the Flash area of the forum and read all the stickies.

AMG wrote in post #2393739
ooh Rene, M is a little scary, but maybe one day. I am dealing with children most of the time, so I need to be able to do what I need to do quickly, This is just family/hobby related stuff, not pro-stuff.

thx peatoire, I will check that out, but will the camera still fire a preflash and adjust the flash output as necessary, or do I lose that function completely ?

I think you lose the pre flash that happens with FEL but you don't lose the TTL function because it fires a pre flash anyway, you just don't see it because it happens so close to the main flash.. The pre flash with the * button just enables it to remember the flash exposure

The only thing I would say is that swapping from CF4-1 back to normal does not lend itself to efficient shooting as you tend to get used to one way or the other. You have to buy in to the whole cf4-1 thing and stick with it or you'll kepp fumbling. There is a very long (and sometimes confusing) thread on it somewhere. This is how I shoot and wouldn't go back

canoflan: I can't see any reason why what I have suggested does not work

peatoire wrote in post #2393859
canoflan: I can't see any reason why what I have suggested does not work

ok, I forgot that a preflash still occurs for flash metering in Av mode.

Also, I recommend 2nd curtain flash.

canoflan wrote in post #2393897
Also, I recommend 2nd curtain flash.

Good way to make sure the subjects eyes are closed, and timing goes out the window

AMG wrote in post #2393588
Hi all, I have a question about AE lock in AV mode while using my external flash as a fill flash. I have read the book, and I am still a little confused. From my understanding, AE works as FE if your flash is on. So, if I want the camera to lock exposure for the background ( outdoors in AV mode ) then how would I do it. You see I don`t want my subject to be considered in the camera`s metering. SO my thought would be to pivot a little until my subject is out of the viewfinder, lock exposure for the background, pivot back and compose, take picture. I guess this workflow is not good simply because I have no AE lock function because my flash is on.

My reasoning for not wanting the subject in the viewfinder while the camera meters is simply because the bigger the difference between the subject and background, the bigger the camera will try and average it out, I want the camera to use the flash to compensate for the subjects exposure, and not change the exposure at all for the background. ( And I would still consider FEC down a bit - still have to experiment with that one )

Is this possible ? thanks a lot all

I'd have to verify this but if you are shooting in Evaluative mode in OneShot mode, the ambient exposure should lock as soon as you half press the shutter button even if you are using a flash. So give that a try. FEL to lock the flash exposure and half-press the shutter button to lock the ambient exposure.

PaceAce: I'm open to be corrected here but I have a strong feeling this will not work, pretty sure you will still only get focus lock.
Why Canon didn't give these completely separate functions their own buttons baffles me more than anything, I think the 1d has separate buttons and the 10D has a programmable extra button. I was exasperated when I found the 5D didn't.

EDIT: Just tried this and you are correct , it does hold AEL.

PacAce wrote in post #2394267
I'd have to verify this but if you are shooting in Evaluative mode in OneShot mode, the ambient exposure should lock as soon as you half press the shutter button even if you are using a flash. So give that a try. FEL to lock the flash exposure and half-press the shutter button to lock the ambient exposure.

99% sure that is correct. That wouldn't allow the OP to lock AF and AE at different parts of the subject however...

If you're in Av mode and using flash, the camera should set the shutter speed to give you a good available light exposure; then the E-TTL system will use the pre-flash to set flash output based on that setting to give you a good flash exposure (as modified by your FEC settings) of the subject. I don't think you even need the exposure lock in that situation unless the subject's under radically different lighting conditions than the background. Of course, if you've set CF 3 to 1 (hold shutter speed to flash sync speed in Av) you'll get 1/200 or 1/250 sec., and an underexposed background, in most any case where it's not really bright.

sorry, when i said pre-flash, I did mean the ETTL immediately before the main flash that you don`t really see.

PACEACE - if I press shutter half way, the focus will lock too, so this does not help me if I am to recompose with me subject, unless I missed something

Jon, what I find is that you are correct mostly but if the subject and ambient light are similar in brightness, what seems to happen is the camera knows you are firing a flash so it knows the subject will be brighter and therefore dials down the exposure to compensate, and then the result shows me a background that lacks punch, clarity and tonal range. I guess when you understand photographym this makes perfect sense, flash reaches subject`s face, but not background so of coarse the subject will eb brighter, but I want the flash to give me the catchlights in the eyes, and the true eye color ( which i find you don`t get without the flash. )

SO my hope is that the camera will set the lowest possible FLASH output, and give me the most balanced shot I can hope for - ASSUMING - like I said that the background and subject are similarly lit. Otherwise, when subject is abitdarker - the camera performs perfectly balancing the subject and background pretty well.

AMG:
The two metering sytems of flash & ambient is a bit of a hurdle to get over when learning them.
The amount of flash output that that ettl works out has no effect whatsoever on the ambient metering. All it is concerned with is distance from flash to subject, once it has worked this out (using the preflash) it knows what flash output is needed based on given values to illuminate the subject ONLY. Try it, put the camera on a tripod and meter a wall, first with the flash on using ttl then with the flash off. Your exposure time will be exactly the same.
TBH, you will find that unless you have very different lighting and you are composing with the subject way off to the edges that the cameras metering should handle pretty well.

peatoire, I understand what you are saying, but the camera is still smart enough to know that I want to use a flash and it also knows through metering that if it exposes for the ambient light, it will over expose my subject, so it makes the necessary calculations so that the subject will be properly exposed, I don`t have my camera, but I am sure, if I remove the flash and look at the exposure it chooses in AV mode, it will have switched from what it was with flash on ( in high sync mode - 420 EX ). So without going in to manual, I want the camera to give me the lowest flash output possible while maintaining an exposure to give me a perfect scenic shot, but I think manual is the only way to have this kind of control.