Max Sync Speed of d-lite 2 & 4?

Lotto wrote in post #6109774
I don't have any experience with the D-lite, so correct me if I am wrong. From reading the responces on this thread, seems to me that the D-lite's internal digital control and sync circuits adds delay on top of the max camera sync speed. Do doesn't matter if the D-lite's flash duration is 1/2000, if it's own circuit adds 1/500 delay to the sync speed, we will not be able to get to the max 1/250. (I don't know how to do the math to get that 1/160.)

Yes, that's what it seems like or something similar based on Robert's experience with his strobes.

Lotto wrote in post #6109774
I don't have any experience with the D-lite, so correct me if I am wrong. From reading the responces on this thread, seems to me that the D-lite's internal digital control and sync circuits adds delay on top of the max camera sync speed. Do doesn't matter if the D-lite's flash duration is 1/2000, if it's own circuit adds 1/500 delay to the sync speed, we will not be able to get to the max 1/250. (I don't know how to do the math to get that 1/160.)

No... if my math above is correct, it means that sync circuit of D-lite adds not 1/500, but something like 1/300-1/350, and it would definitely help if its flash duration was 1/2000, since even with current circuitry and that flash speed I think it would be able to do 1/250 sync. (not with it's 1/800th as it has right now)

bomzai wrote in post #6113273
No... if my math above is correct, it means that sync circuit of D-lite adds not 1/500, but something like 1/300-1/350, and it would definitely help if its flash duration was 1/2000, since even with current circuitry and that flash speed I think it would be able to do 1/250 sync. (not with it's 1/800th as it has right now)

It doesn't really matter what the flash duration is because that doesn't make the black bar appear in the picture. If the sync speed is not long enough to capture the full duration of the flash all you get is an underexposed image but not a black bar. But what is important as far as getting a black bar in the frame or not is how fast strobe fires and reaches peak power after being triggered. The longer that is, the wider the black bar.

I'll try some experiments to see if I can determine what that time is (it'll vary from camera to camera, I'm sure). Stay tuned.

Using a MultiMax, I was able to introduce a variable amount of delay to the sync trigger going to the flash.

With the 1Dmk3, I was able to delay the sync by 0.0015 of a second (1/666) without any dark bar showing at the bottom of the frame. With a delay of 0.0016 (1/625) sec., a dark (fuzzy) bar was just starting to appear and at 0.0017 (1/588 ) sec., a distinct black bar was visible.

With the 30D, the dark bar appeared at 0.0015 of a second (1/666).

So, in either case, if the strobe or flash introduced a delay of 1/500 sec., you would definitely get a black bar in the picture at a shutter speed of 1/250, resulting in a usable max sync speed of only 1/160.

Great experiments! As I see it we basically agree that the main point in sync-ing is the delay before flash starts firing.

But I see your point that with 1/250 shutter, if your initial delay is long enough (~1/500) then no matter how fast is the flash, it's too late, because part of the sensor is already covered by shutter at that time.