580EX: Can you explain TTL mode and why the flash doesn't fire?

[TMR Design]

I was just playing around with my 580EX and remember seeing that Custom Function 3 is used to toggle between ETTL and TTL so I decided to switch to TTL and check it out. I guess I don't understand how this is supposed to work because no matter what I did in TTL mode the flash would not fire.

Does anyone know why this would be and perhaps shed some light (eek, bad pun) on this subject? Are there other settings I have to check to use the flash in TTL mode?

[scottbergerphoto]

TTL isn't designed to work with Canon digital cameras. In TTL metering there is no preflash metering with the shutter closed as there is in ETTL. Metering of the flash in TTL is done with the shutter open with a flash meter inside the camera at the film plane, measuring the actual flash output and turning off the flash when enough light has been recieved. It is designed to work with film cameras. In ETTL the flash output is determined before the shutter opens by the amount of preflash returned to the camera from the subject.

[Wilt]

TTL mode is for older film SLR which metered during the actual exposure (not using a preflash). TTL-controlled flash units do not work with ETTL cameras.

Put your 580EX only in ETTL mode for use with your 30D.

[TMR Design]

Thank you. That information was nowhere to be found in the manual. I've been using ETTL and Manual but thought it was something I was missing.

[PacAce]

Just as an FYI, current EOS film cameras can also use TTL, in addition to ETTL. It's only the digitial EOS cameras that's restricted to ETTL. :)

[PacAce]

Thank you. That information was nowhere to be found in the manual. I've been using ETTL and Manual but thought it was something I was missing.
There are references to TTL in page 2 and page 53 in the 580EX manual although they don't go into too much detail.

[Curtis N]

That information was nowhere to be found in the manual.FYI, the EOS Flash Bible describes both systems with good detail.

[scottbergerphoto]

The EOS Flash Bible (http://photonotes.org/articles/eos-flash/)

[Lacks_focus]

Simular(ish) question. I did search to find an answer, but there was nothing difinitve. I am considering a 580EX. Right now I don't have a flash other than the pen light that sits on top of my 10D's view finder. I sold my 540EZ along with my EOS 1n. ATTL (EZ) flashes do not work, except in manual mode, on ETTL cameras. I miss not having a dedicated high power flash!

My question is, will the 580's ETTL II work on my 10D. I understand the 10D supports ETTL and that the 580 will work fine, but will it make use of the ETTL II capability of the 580? Another words, is ETTL II simply a function of the flash, or does it need to be supported by an ETTL II capable camera? I know the 20D, 30D, and I think even the 7NE film bodies are advertised as ETTL II, but does that mean the 10D is not?

[René Damkot]

ETTL2 is a function of the body. The 10D uses ETTL (1).

[Lacks_focus]

ETTL2 is a function of the body. The 10D uses ETTL (1).

Figured as much... Thanks. I was thinking if that was the case, I should go for a used 550EX, but knowing me, I'll upgrade the body in the next year or so. Better just get the 580 and be done with it!

[René Damkot]

550EX will also use ETTL2 on, say, a 1DMk2 or 20D body.
I'd get a 580 (or 430 for that matter) over a 550 however, for ergonomic reasons.