Sync speed, canon 7d and Elinchrom d-lite rx 1, and skyport sync

[coldpenguin]

Am I expecting too much, or am I doing something wrong here?


I bought the two head kit, 280084 I think, it comes with two D-Lite RC One, and the Skyport speed transmitter.
I am using it with the Canon 7d, with the sync cable plugged into the transmitter from the camera.

I have set both heads to be mode r2,
I have pressed the test button on the transmitter untul it flashed twice

However, above 1/250s I am getting a slight black bar on the bottom of the frame, suggesting I am not getting a full sync.

Ah, I see the problem. An SLR only syncs at 1/250, however a compacy can sync at 1/1280? How come the SLR has a slower sync?

 

[HoppyUK]

7D's max x-sync speed is 1/250sec. It's a limitation imposed by the focal-plane shutter, as found in all DSLRs.

There is a technique to go higher that works with many studio-type heads called Tail Hypersync but it's a bit of a bodge/hack with some major drawbacks, in particular, greatly reduced brightness and uneven exposure down the frame.

 

[Phil V]

Any reason you need a faster sync?

 

[coldpenguin]

No, I don't think so.
The 'model was a baby, so wasn't particularly happy about staying still, but 1/250s should be enough.

It is just that when I started to 'test' them, I had the kit set in non-speed mode, and the shots were disappointingly dark, at 1/50 (still object). (needed two heads 250Ws on a full power, 1/50, F-7 ISO 100, and it was still dark).
When I turned on the fast-sync mode (was off on both TX and flash before, which should have meant a 1/200 sync max), they were a lot better, power was at ~0.7 on each head out of 4.0, T 1/250, F-7, ISO 100.

I was wondering whether for some reason the camera is getting through the frame too fast (which it seems to be) when it shouldn't be.

 

[HoppyUK]

No, I don't think so.
The 'model was a baby, so wasn't particularly happy about staying still, but 1/250s should be enough.

It is just that when I started to 'test' them, I had the kit set in non-speed mode, and the shots were disappointingly dark, at 1/50 (still object). (needed two heads 250Ws on a full power, 1/50, F-7 ISO 100, and it was still dark).
When I turned on the fast-sync mode (was off on both TX and flash before, which should have meant a 1/200 sync max), they were a lot better, power was at ~0.7 on each head out of 4.0, T 1/250, F-7, ISO 100.

I was wondering whether for some reason the camera is getting through the frame too fast (which it seems to be) when it shouldn't be.

This doesn't quite stack up

Shutter speed makes no difference to flash exposure, so long as it's kept below 1/250sec max on a 7D. The flash duration is your effective 'shutter speed' and that's pretty nifty on a D-Lite One. There are some qualifications to that, and the 7D handbook says use 1/60sec with studio flash (p130). You can ignore that though, it's mega cautious, and rule of thumb these days is 1/125sec and that works fine with pretty much all DSLRs and all types of flash unit. In Skyport's non-speed mode.

There is normally no need to use faster shutter speeds than that in the studio - it makes no difference to the exposure and could, with some combinations of equipment, cause minor issues. However, you do have the option to go up to 1/250sec with your kit and that would be useful if the ambient light was high enough to influence the exposure - say bright sun coming through windows, or working outdoors. Then use the Speed mode, but it will drain the trigger battery more quickly.

 

[coldpenguin]

This doesn't quite stack up

No, I didn't think it did. Next time I have the kit out I will set it back to normal mode and try to recreate the problem. Difficulty is that the baby is now mobile, so I can't really leave the kit up without it being messed with.