What in the ETTL is going on?!?!?

So here is an extreme scenario I just created to prove a point.... Because I am totally not understanding my 580 EX II and this ETTL....


I understand its suppose to be EZ MODE for flash setup on-camera (and with all the popper talk lately, im sure off-camera as well) and im not suppose to have to worry about much. But here is what happens:


Flash mounted on camera, all batteries are fresh (both camera and flash). Set camera to AV MODE @ 2.8, ISO @ 100. Flash set on ETTL mode. Pressing the shutter half way, I get a 5" shutter time (im shooting the interior of my car in a garage)...which of course I cant hand hold anything beyond 1/60th.... (I just did this as an extreme) and take the shot....okay....whatev​ers....

Then I set the camera to FULL AUTO MODE, focus, and take a shot. Check the info, and what do i get?? 2.8 ISO @ 400, shutter speed 1/60!!!! Fair enough... I go back to my AV mode...to match the ISO that AUTO set it too...which is 400, and meter through the camera......I still get 1.5" shutter speed!!

Why am i getting 2 diff readings with the same exact composed shot?? ETTl not working for me.....Camera is at factory settings, and AV metering is evaluative... I dont want to be limited at shooting in full automode, having no control at all about aperture and such...

AV, TV, M and full auto all use different flash metering methods. Shooting in P or any auto mode(except night time) will lock the exposure at a minimum of 1/60 when using the flash. Shooting in av will meter the scene based on available light and use the flash as fill. Checkout this link for some great information on using your flash

I always shoot in manual mode when shooting with a flash. In AV mode, the camera is metering the scene, it doesn't care about the flash (its used for fill). When you shoot in AV mode it will adjust the SS for the metered scene and take a picture. The flash will fire in a manner that doesn't completely overpower the metered reading. What you want to do is work in manual mode in which case the flash will know what the camera is doing and decide how much light it needs to put out to get the correct exposure.

Woot got it with some explanation.... Imma have to test it out and get back to you guys personally if you dont mind. Thanks for the info!

Dont know why they say you can use ETTL in other modes when its not effective...

In Av, Tv, and M, the scene is metered for a standard exposure and the flash is used for fill. In P or Auto, the flash is used as the main light and the shutter speed isn't let to drop slower than 1/60th.

EDIT: Oops! Took too long on something else and it looks like you got your answer. ETTL works well in other modes as long as you pay attention to what you're doing. In manual ETTL works just fine. There's also a custom function (on my camera, don't know about yours but there should be) that when in Av mode the camera will be set to the sync speed when the flash is enabled. Don't know if that helps you any, but it might.

seed808 wrote in post #8483535
Dont know why they say you can use ETTL in other modes when its not effective...

I have used E-TTL in Av and Tv modes and both the camera and flash performed as expected.

When you choose those modes, you're saying you want the camera to select the shutter speed or aperture for correct ambient exposure. If that's not what you want the camera to do, there's no reason to use those modes.

Here is a sequence of shots that I took to illustrate what happens without flash and with ETTL flash, in M and Av and Tv and P mode. All shots assume ISO800. Ambient lighting was halogen track lighting in my family room. Blue text indicates photographer controlled parameter; black text indicates camera-selected parameter. Note that the incident meter indicates the combination of f/stop and shutter speed (1/15 f/5.6 +0.2EV) for the light striking the scene, while the camera's own Spot meter saw the area between the meter and the stuffed toy and read the exposure to be a bit darker, so it chose 1/15 f/4.5 as the needed exposure.


In sequence A, no flash:
M 1/15 f/4.5
Av 1/15 f/4.5
Tv 1/15 f/4.5
P 1/40 f/2.8

The results are identical although the camera chose the different shutter speed and f/stop when in P mode. ( I altered WB in post processing the eliminate the excessive warmth of halogen lighting while the as-shot camera was set to Daylight WB.)

joshr03 wrote in post #8483489
AV, TV, M and full auto all use different flash metering methods.

It's more or less explained in the posts following the one I quote here, but to avoid confusion I'd like to correct this into that Av, Tv and M metering for ambient light is focused on the correct exposure using available light only. Then the flash is added to that.
If you use P mode, the camera will expose ambient light correctly only if it's reasonably light, i.e. possible to do with selected ISO, full aperture and 1/60 s. Otherwise it gives up and let the far away shadows stay dark.
Green box mode does the same.

But metering of the flash is the same in all modes and separate from metering of ambient light.

If you want to use Av, TV, e.t.c. you can dial in exposure compensation on the camera to adjust the ratio between ambient light and flash. if you're using bounce flash for example, you can shoot in Av mode with -2 dialed into the camera to keep the shutter speed up and the ISO down, and the flash should simply add whatever light is needed to expose the shot properly.

apersson850 wrote in post #8485177
It's more or less explained in the posts following the one I quote here, but to avoid confusion I'd like to correct this into that Av, Tv and M metering for ambient light is focused on the correct exposure using available light only. Then the flash is added to that.
If you use P mode, the camera will expose ambient light correctly only if it's reasonably light, i.e. possible to do with selected ISO, full aperture and 1/60 s. Otherwise it gives up and let the far away shadows stay dark.
Green box mode does the same.

But metering of the flash is the same in all modes and separate from metering of ambient light.

^^^ These points illustrated in my posted example series. The fact that the camera-chosen parameters were identical, regardless of flash off or flash on, proves what was said.

Just read THIS.

First of all Id like to thank everyone for all of their input... I understand ETTL much more since I have started the thread...

I now understand that the "flash" evaluates how much light it needs to output, but that doesnt change any settings in the camera itself....which I thought it might do...

I understand the concept of shooting in M as well. Maybe ETTL isnt my issue now. But lets say for instance, im shooting a wedding indoors, or a nightclub.... I dont really want to spend the time constantly adjusting my SS for proper exposure in manual. For these images, I dont mind the background being in the dark somewhat, as long as the subjects in front of me are lit well (as in a dark nightclub). Now if I have my 580 on camera in ETTL, camera in M or AV mode, more than likely my SS would be to slow for me to handhold. I dont want to shoot in auto modes and be limited to being wide open all the time (as in a wedding, sometimes you want to add DoF to the images)... I also PP in Lightroom, so I always work with RAW image files... Green Box = JPEG....

Im coming to the conclusion that it comes down to experience and knowing what SS I need to be in manual... My friend just told me thats what probably separates the noob photogs from the good photogs....

seed808 wrote in post #8487821
First of all Id like to thank everyone for all of their input... I understand ETTL much more since I have started the thread...Im coming to the conclusion that it comes down to experience and knowing what SS I need to be in manual... My friend just told me thats what probably separates the noob photogs from the good photogs....

You understand well!

Let me ask a related question. I was also experimenting with this last night. My subject was outside, and I wanted the subject to be properly illuminated while darkening the background slightly for better contrast. I used AV mode with the aperture I wanted to see what the camera chose for shutter speed. It chose 1/60 in this case. Then I switched to M mode, used the same aperture and doubled the shutter speed to 1/125 and switched on the flash. It did pretty much what I wanted. I used evaluative metering of the scene though, and my subject was a little bit underexposed. Should I have used partial or spot metering on the subject to make sure he was properly exposed?

sdipirro wrote in post #8488027
Let me ask a related question. I was also experimenting with this last night. My subject was outside, and I wanted the subject to be properly illuminated while darkening the background slightly for better contrast. I used AV mode with the aperture I wanted to see what the camera chose for shutter speed. It chose 1/60 in this case. Then I switched to M mode, used the same aperture and doubled the shutter speed to 1/125 and switched on the flash. It did pretty much what I wanted. I used evaluative metering of the scene though, and my subject was a little bit underexposed. Should I have used partial or spot metering on the subject to make sure he was properly exposed?

You started right but the underexposure is not unexpected. Do neither (partial/spot)...ETTL with Canon flashes commonly underexposes, typically about 1EV, so the fix was to dial in FEC = 1

(BTW, with my 20D my Canon 54MZ would underexpose by 1EV so when flash was main source of light, FEC = 1 was typical (sometimes a bit less). Oddly, the same flash under my 40D control doesn't seem to underexpose, so I leave FEC = 0 most of the time for flash as main light source.)