Paul C. Buff, Inc. Technical Forum

There seems to be some confusion as to the sync speed of our remotes and lights. I hope this will clarify...

"Sync speed" refers to the maximum shutter speed at which your camera can capture an entire frame that is exposed by a flash. In today's cameras, this is typically about 1/160 to 1/250 of a second. Cameras trigger a flash as soon as the first curtain opens (rear sync works slightly different, but will have the same effect). At your sync speed (x-sync) and below, the rear curtain is still out of the way, and not blocking your image sensor (or film). At speeds above your x-sync, by the time the first curtain opens, the second curtain has already started its travel across the frame, blocking a portion and resulting in a black bar, typically running horizontally, either at the top or bottom of the frame. The more you exceed the x-sync, the bigger the black bar gets.

When using a radio remote, like CyberSync, Pocket Wizard, Cactus, etc., there is an inherent delay. This delay varies from one manufacturer to another. Sometimes, the delay exceeds a camera's x-sync, causing black bands, despite the camera's ability to operate at that speed. Example: an inexpensive remote will have a delay to where the remote's sync speed is 1/60, but your camera will sync at 1/250. To avoid the black bars, you will need to shoot at 1/60.

We advertise the CyberSync to sync at 1/2500 of a second. This means you can sync at your camera's maximum sync speed up to 1/2500 of a second. If your camera's x-sync is 1/160, you can shoot 1/160 or slower. This does not mean you can automatically shoot 1/2500 on any camera with CyberSync, as the x-sync is a physical limitation of your camera.

Some cameras, particularly point-and-shoots with a hotshoe, and some (older) Nikon DSLRs, use an electronic shutter (the DSLRs use a hybrid shutter) that effectively start sensing/stop sensing, rather than using a moving shutter. This allows the entire frame to to be "exposed" simultaneously, thus achieving higher sync speeds. We tested (on a Nikon D40) and found our CyberSync to not be the limiting factor up to 1/2500 of a second, when the camera has that high of a sync speed. Some well-regarded remotes publish a sync speed of about 1/500 of a second, making ours five times faster.

Sync Speed vs. High Speed Sync vs. Hyper Sync will be discussed in a separate thread.


TS

if you want to push your camera over the sync speed and yet still get a flash to work, consider that the "black bar" or the unexposed area of the photo is typically on the bottom of the shot. So, consider that if the subject of your photo has an area over their head that is exposed by ambient (sky, something in the distance that is not exposed by the flash), you can always flip your camera upside-down and get the flash to expose your subject and no one would have any idea you were beyond your sync speed. :mrgreen:

I'm using a Nikon D700 (1/250th Sync Max), but when normally shooting at 250th with flash, I notice that about 1 in every 4-5 shots or so using either CST or CC with a CSRB+ on a speedlight (SB900) I'm getting the black bars. Annoying to say the least.

While it's usually set to 1/250* AutoFP (Hi-Speed Sync) I've tried setting the camera's max sync on the setup menu's to 1/250 with AutoFP off, but am getting the same black bar results. I'm not sure what else to check.. Hoping not to have to jump down to 200th or lower.. Any ideas?

What is the time between shots? If left for too long (typically 30 sec. is default, but it can vary), the SB900 will go into sleep mode. When triggered, it will not wake up and fire at the appropriate time. The auto sleep mode can be extended, or evern shut off, via menu options.

The flash is definately firing off.

I am not saying the flash will not fire, but it may start a fraction of a second too late.

Cool, thanks!

The banding was happening closer to full power, less often for 1/4, 1/8 & so on at 250th less at 200th and almost never at 160th or lower - so that got me thinkin' about your post on shot-to-shot timing.

I guess I wasn't paying much attention to the indicator when firing test shots since I was only shooting about 5 frames or so every couple of minutes for the test - but the speedlight was firing off even though it wasn't fully recycled (at the risk of pushing it's temp way up).

So I was looking for the recycle indicator on the flash to reset before popping off more. Now, at 1/2 power or lower I'm able to shoot at about 3.5fps with clean recycles without banding, not that I'll realistically do this very often, but just as a test for the banding/sync issue. As far as the tidbit on the auto-sleep function, I'll certainly keep that in mind.

Anyways, Thanks again! =]

Hmm. it should fire and evenly cover the frame, even if it is not fully recycled, just at a lower intensity. Is the black bar coming from the top or bottom? are you in rear curtain sync?

No, it's not on Rear or Slow sync. It was happening alot when I was first fooling around with the CS's but less often now, more than likely dumb-user error. :oops: In fact, last night I couldn't get it to occur but I was waiting for full recycles.

When I do get the band, it's on the bottom, and usually it's the first of any images shot, which makes me wonder if that auto-off delay is the culprit. The top 20% or so of the image is discernible, the rest is black from the middle downwards. Strange thing is the exposure looks to be close to the same from the images without the band, which doesn't make sense.. as you said, it SHOULD be darker as there would be less light entering the frame since the curtain would effectively block it, correct?

A sync error in studio would cause a portion of the frame to be "properly" exposed (assuming otherwise correct settings), and another portion to be completely black, seperated by a very harsh line.

Outside, the entire frame could have exposure, since sunlight is also exposing the sensor. However, that which is lit by flash would be brighter (some use this to thier advantage to "cheat" the sync speed, sometimes by turing the camera up to 180 degrees).

Sync errors can result from too fast of a shutter speed (not always what the camera mfg states, but Nikon seems pretty good), a lag from the remotes (CS is 1/4000 of a second, so is a non issue), or a lag introduced by the flash. Flash lag can be electronic, awakening from a sleep mode (thus firing a bit late), or the flash duration (the last one is not an issue with speedlites, and would typically result in a faded line).

I also assume you are not in SU-4 mode or any other wireless commander/slave setting? if not, everything points to sleep mode.