Canon 40 D - Rear Curtain Flash Sync ( Second Curtain Sync )

[JessicaLuchesi]

Hello everyone,

I am currently planning a fashion photoshoot, done by night with long exposure mixed with the models. Everything is planned and defined as far as looks and so on, but I want to be able to use rear curtain sync, instead of front ( or first ) curtain sync. I researched it and found out it's possible on the Canon 40D, set it up with my 580EX tied to my camera. The thing is... I don't want to use the 580EX II, I want to use an external flash unit ( brand is irrelevant really ), fired with a radio unit, remotely.

Is there any way to have the 40D rear curtain sync work like you'd expect it to? ( in a short, triggering the flash port and the sync cable port on rear curtain instead of the first one )

Anyone know of any newer firmware (I'm on 1.1.1, which is the newest I could find on the Canon site ), or a work-around, or maybe alternative firmware that allows for this?

Thank you so much for your input. I do have one makeshift solution for this, which is to use a photo sensitive cell linked to a PC card fire my radio unit in my pocket. And I ducktape the cell to the built in flash. Yeah, VERY makeshift and unwanted, even more when you know your camera has a built in function that is ALMOST there. I mean, it has second curtain capacity, it has a PC cable slot, why can't it just trigger it as it should, without needing complex handshakes with brand-owned models of flashes? I could want to hook it to a broncolor set for a studio photoshoot after all, this is creatively very limiting from Canon's side.

So, fingers crossed here for a more elegant, cleaner, smoother, better solutions from you all  Thank you in advance for the help

[JessicaLuchesi]

By the way, just checked Pocket Wizard's FlexTT5's manual, rear curtain sync is not supported

[JessicaLuchesi]

I fidgeted a bit more with it here...

Thinking about it, all I can think about is that the rear curtain flash sync on the Speedlight series works by having the flash count ms from the actual camera flash firing command on the hot shoe, and then fires on it's own. If that's so, that's why when I connected my normal radio unit, it trigged the normal way and fired at first curtain. So, if I'm correct, instead of the camera firing at second curtain, Canon developed it in a way where the flash does all the math, since it knows the exposure time, and if the flash doesn't know how to handle it, you don't get rear-curtain flash. Because, I guess, Canon cameras trigger the flash always at first curtain, maybe it's something built in the actual mechanics of flash design and the flash isn't software triggered, but hardware triggered and rear curtain is actually a software walk around in the flash to allow for it. Kind of a rear curtain emulation, not a real rear curtain mechanism.

Would me much simpler to have the camera trigger all flash ports by software itself, so that the camera could fire first curtain, rear curtain, or with any ms programmed delay. Just like the flash does internally.

Also, it means Pocket Wizard could emulate this behavior by software someday, and a patch could solve it. Hopefully.

[Lightbox]

The only way I have got second curtain sync to work is what you have mentioned in your first post, gaffa an optical slave to a 580 mounted on camera, and then cable this to a Pocket Wizard. It isn't that bad of a work around and works 100%, but sure would be nice if second curtain sync was controlled by camera and available regardless of setup.

[Ken Bennett]

Using an optical slave gaffer-taped to the flash will work fine as long as the flash is set to manual output -- otherwise the pre-flash will fire your strobes before the shutter is open.

I used to do this all the time in the studio to fire my studio strobes. I would set the 580 EX to 1/64 manual power, and point it at the ceiling. That flash would fire the monolights. The 580 EX output had no effect on the overall exposure. There is no reason why this shouldn't work in second-curtain sync mode.

I don't think the built-in flash can be used this way, since it's always in TTL (but I could be wrong about that -- I don't think I've ever used the built in flash on my 40D.)

[JessicaLuchesi]

Using an optical slave gaffer-taped to the flash will work fine as long as the flash is set to manual output -- otherwise the pre-flash will fire your strobes before the shutter is open.

I used to do this all the time in the studio to fire my studio strobes. I would set the 580 EX to 1/64 manual power, and point it at the ceiling. That flash would fire the monolights. The 580 EX output had no effect on the overall exposure. There is no reason why this shouldn't work in second-curtain sync mode.

I don't think the built-in flash can be used this way, since it's always in TTL (but I could be wrong about that -- I don't think I've ever used the built in flash on my 40D.)

Hi, to be honest, I didn't test the rear curtain with the internal flash, only with the 580, and I saw the firmware allows the same for the internal one, so, I guess it will work to. No preflash was fired. That is for now the solution I have, but if pocket wizard had it's new line of TTL radio units working with rear curtain, I'd be sure to buy some right away. I don't mind too much using this kind of solution, but I do mind the make-shiftness of this being caused for what I consider a design flaw on Canon's side. I mean, this is better than nothing, but short of being a proper way of doing it.

[Ken Bennett]

... I do mind the make-shiftness of this being caused for what I consider a design flaw on Canon's side.

Well, you would not be the first photographer to point out a design flaw in the Canon flash system.

http://pixsylated.com/2009/07/syl-arena-ca...dlite-wishlist/

--Ken

[Ken Bennett]

Jessica,

I brought a 40-D body to the studio this morning for further testing. As far as I can tell, the 2nd-curtain sync option in the camera body is for the internal flash only. It has no effect on any sort of external flash, either a Canon speedlight or a radio trigger. (In fact, with any sort of external flash or trigger attached to the hot shoe, the camera won't let me choose that menu item.)

Then I tested the 40-D internal flash triggering an optical slave on my studio lights. This did not work: the pre-flash fired the studio lights, so they didn't fire during the main exposure. It didn't matter whether the internal flash was set to 1st or 2nd curtain sync. I don't see any obvious way to use the internal flash on manual, or to disable the pre-flash.

Finally, I tested a Canon speedlight (580 EX) in the hot shoe. On E-TTL, it doesn't work at all (same problem with the pre-flash.) But on Manual output, the 580 EX fires the remote lights on either 1st or 2nd curtain sync, very reliably. I set it to 1/64 power so it had no effect on the overall exposure. The 2nd curtain sync was set on the flash unit.

So it sounds like your original solution is the best option. If you dial down the output power of the speedlight, you might not need to tape the optical slave to the flash, which might look a little better to the models and the client.

Cheers,

Ken

[Conner999]

Tape an IR gel over the flash head for a powerful, zero-contribution trigger - regardless of where the on-camera flash is pointed.

I used this all the time  with an SB-24 (in M mode) and one of those velcro-on gel holders before I went to Skyports. Just cut a section of IR filter gel to fit inside the gel window, gaffer any slivers that the gel doesn't block -- or just gaffer one over the flash head, blocking all visible light. Instant zero-contribution flash trigger.

At any decent power setting any decent flash head will trigger every studio strobe in the area. If you're doing a LOT of full-power rapid fire triggers, the head may get a bit hot. In this case, have two 580s and rotate them if your in continuos rapid-fire mode.  

[Bill Allsopp]

So glad to find this thread. Just about ready to chuck the baby out with the bathwater.