580EX, E-TTL-II, & Dynamic Range

[Mark_48]

I've caught the following excerpt from a Canon news release about the 580EX a couple of times and I'm not sure how to interpret it.

The Speedlite 580EX flash is compatible with Canon's E-TTL II (Evaluative Through The Lens) auto exposure technology. When combined with a compatible Canon camera, E-TTL II utilizes subject distance and other information that automatically modifies flash power, resulting in accurate flash exposure regardless of subject size, reflectance, or photographic composition. This is great news for photographers that shoot high contrast or reflective subjects, like those encountered in wedding photography. Photographers can now capture every detail from the black of tuxedoes to the white of wide smiles and wedding dresses.

Does this in any way suggest that using the 580EX with E-TTL II can extend the dynamic range of a camera somehow that with previous flash units and E-TTL weren't achievable? I've always had difficulty with the extremes of blacks and whites which I believed to be the limitation of the cameras dynamic range, not so much a function so much of the flash used or metering involved. My current setup is a 20D and 420EX and I'm looking at a possible upgrade to the 580EX. From what I've read the 420EX should work with cameras E-TTL II performing the metering and control. Just wondering how the 580EX could improve on this or if it really does.

Mark.....
(If this post should appear a bit incoherent, I'm waging battle with a touch of the flu...)

[PacAce]

Althought that highlighted quote seems to imply that it just applies to the 580EX flash, that's not the case. It applies to all EX flashes.

[René Damkot]

Canon is basically saying that with a (fill) flash you can lower the contrast on your subject . . .

[darthfocus]

Heres the deal, TTL2 is in the 20D not the 10D, TTL 2 has nothing to do with the flash, its all about the body. The 580 is a slighty more powerful version of the 550 with easier controls. You'd be better off using an auto thryrister strobe anyway, TTL2 or TTL just plain stinks 20% of the time.

[PacAce]

Heres the deal, TTL2 is in the 20D not the 10D, TTL 2 has nothing to do with the flash, its all about the body. The 580 is a slighty more powerful version of the 550 with easier controls. You'd be better off using an auto thryrister strobe anyway, TTL2 or TTL just plain stinks 20% of the time.
And auto-thyristor flashes have their own set of indiosyncracies. The bottom line is that there is no such thing as a perfect flash and whether it's an auto-thyristor or an ETTL flash, it's all a matter of knowing their particular characteristics and learning to deal with it.

[DaveG]

Ah, all those flashes are auto thyristor. You guys mean Automatic rather than TTL.

[PacAce]

Ah, all those flashes are auto thyristor. You guys mean Automatic rather than TTL.
Yes, all thoes flashes are thyristor controlled but I think auto-thyristor usually implies self contained flashes and not TTL flashes. Of course, I could be wrong, too. :)

[DaveG]

No.

If you are using a flash and it needs only 20% of the stored power to make the correct exposure the auto thyrister is the circuit that takes that unused power and dumps it back into the capacitor. This improves battery life and speeds up recycling. "Auto Thyristor" is on the front of a lot of Automatic flashes because it was a big deal when flashes started using them in the 1970's, but that circuitry is certainly part of any TTL flash sold today. I had a non Auto Thyristor Automatic flash (a Strobonar) and when it needed 20% power the sound of the power being dumped (and wasted) was like the crack of a whip. Auto thyristor doesn't mean Automatic or preclude TTL flashes so its use this way is misleading.

[PacAce]

No.

If you are using a flash and it needs only 20% of the stored power to make the correct exposure the auto thyrister is the circuit that takes that unused power and dumps it back into the capacitor. This improves battery life and speeds up recycling. "Auto Thyristor" is on the front of a lot of Automatic flashes because it was a big deal when flashes started using them in the 1970's, but that circuitry is certainly part of any TTL flash sold today. I had a non Auto Thyristor Automatic flash (a Strobonar) and when it needed 20% power the sound of the power being dumped (and wasted) was like the crack of a whip. Auto thyristor doesn't mean Automatic or preclude TTL flashes so its use this way is misleading.
It's been a while but if I recall correctly, it was the introduction of the thyristor into automatic flashes which made automatic flashes without wasting capacitor charges for partial firings possible. Before the thyristors came around, as you said, even partial flash output used up the full charge on the capacitor. Hence they had the auto flashes (no thyristor component in flash) and the auto-thyristor flashes (to differentiate them from your regular auto flash).

Anyway here's a quote from another source (http://photonotes.org/cgi-bin/entry.pl?id=Thyristor) that supports what I was trying to say in my previous post about the generic use of the term auto-thyristor (the bold face is mine):



Thyristor (auto thyristor).

A semiconductor (electronic component) used in photography to control electronic flash tubes.

Thyristors are switch devices which allow current to pass through when a third conductor has a control voltage applied. They’re commonly used in electronic flash units for this very purpose - they allow high-voltage electricity to pass into the flash tube, creating light, until the lower-voltage control voltage is dropped, at which point the light is extinguished. If the flash unit is not fired at full power then the main storage capacitor is not fully drained, unlike older units which wasted a full charge even if the flash was fired in a low power mode.

Most electronic flash units these days contain thyristors, but the term is generally associated with the first generation of automatic units which employed thyristors - auto-thyristor flashes (see automatic flash unit). Since there’s nothing particularly remarkable about thyristors today the term generally isn’t used as a marketing tool anymore.

[DaveG]

My point is that I'd like to see Automatic flashes continue to be called Automatic flashes. That term neither excludes Automatic flashes like my old Strobonar which was Automatic, nor does it include TTL flashes which Auto Thyrister should. How can you exclude TTL flashes from Auto Thyrister when they most certainly have it?

To call an Automatic flash "Auto Thyrister" and have that term replace Automatic is wrong since we all agree that there ARE auto thyristers inside TTL flashes.

[PacAce]

My point is that I'd like to see Automatic flashes continue to be called Automatic flashes. That term neither excludes Automatic flashes like my old Strobonar which was Automatic, nor does it include TTL flashes which Auto Thyrister should. How can you exclude TTL flashes from Auto Thyrister when they most certainly have it?

To call an Automatic flash "Auto Thyrister" and have that term replace Automatic is wrong since we all agree that there ARE auto thyristers inside TTL flashes.
I'm sure this is going to go nowhere because we can just ping-pong back and forth here. Are you trying to say that a TTL flash is not an automatic flash? I'm sure there are people who will think that a TTL flash is an automatic flash.

And by the same token, I don't agree that a TTL flash, although it may have a thyristor component inside, can be classified as an auto-thyristor flash because the intelligence that controls the thyristor is not within the flash but in the camera itself. After all, isn't ETTL and ETTL-II implemted by the body and not by the flash?

[PacAce]

OK, I see where you're going with all this. What you're trying to say that we should just call all stand-alone automatic flashes as "automatic" flashes and just drop the "thyristor" all together since all automatic flashes nowadays have thyristors in them anyway. If so then I guess I don't have any qualms about that. I thought that you were arguing what the term "auto-thyristor" really was. I just use it out of habit 'cuz I "lived" through that era. But you're right, anybody who hasn't won't really "get it" and might just be confused. :)

[DaveG]

I'm sure this is going to go nowhere because we can just ping-pong back and forth here. Are you trying to say that a TTL flash is not an automatic flash? I'm sure there are people who will think that a TTL flash is an automatic flash.

And by the same token, I don't agree that a TTL flash, although it may have a thyristor component inside, can be classified as an auto-thyristor flash because the intelligence that controls the thyristor is not within the flash but in the camera itself. After all, isn't ETTL and ETTL-II implemted by the body and not by the flash?

When you use a Vivitar 283 you can choose Manual or Automatic settings. Automatic is when you select f8 on the flash and set f8 on the lenses' aperture. The Canon EX flash's have NO Automatic settings, they have E-TTL settings.

It's too bad that Automatic (and I'm careful to capitalize it) was the term chosen for this feature. Mostly because automatic (no caps) has a connotation in the real world. Like the word "Credit" or "Debit" beginning accounting students put real world meanings on those words instead of their accounting meaning which is "left" and "right"; and then they confuse the heck out of themselves! Of course E-TTL flashes are automatic, but they are not Automatic.

The auto thyrister is a very dumb circuit and I'm sure it's contolled by the flash. All it does is it redirects the unused capacitor power back into the capacitor. The camera in the Canon flashes may well control how much of the capacitor's power to use but the auto thyrister circuits are inside the flash.

If you want to call the older Automatic flashes "Auto Thyrister" you could call the camera themselves "flipping mirror SLR's". Now the digital cameras still have "flipping mirrors" but if you think that common features differentuate different products then go ahead. There are Auto Thyristers in both kinds of flashes, but both flashes are not Automatic.

[DaveG]

OK, I see where you're going with all this. What you're trying to say that we should just call all stand-alone automatic flashes as "automatic" flashes and just drop the "thyristor" all together since all automatic flashes nowadays have thyristors in them anyway. If so then I guess I don't have any qualms about that. I thought that you were arguing what the term "auto-thyristor" really was. I just use it out of habit 'cuz I "lived" through that era. But you're right, anybody who hasn't won't really "get it" and might just be confused. :)

Exactly. I just think that Automatic is accurate and "Auto Thyrister" isn't.

[PacAce]

Exactly. I just think that Automatic is accurate and "Auto Thyrister" isn't.
Well, I wouldn't go that far but suffice it to say that "automatic" is accurate enough. Period. :)