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This was of some interest to me because I have been getting the horizontal bars, so I did a lot of research and some testing. My camera has a nominal sync speed of 1/200 and I am using Britek PS-200 and PS-250 strobes which have a flash duration of 1/1500s. My interest was because I noticed a significant difference when firing just one strobe with a radio trigger and using the built-in optical slaves on the others against having radio receivers on all of the strobes.

This was of some interest to me because I have been getting the horizontal bars, so I did a lot of research and some testing. My camera has a nominal sync speed of 1/200 and I am using Britek PS-200 and PS-250 strobes which have a flash duration of 1/1500s. My interest was because I noticed a significant difference when firing just one strobe with a radio trigger and using the built-in optical slaves on the others against having radio receivers on all of the strobes. I did some testing and worked out that my curtain speed (the time from the curtain starting its travel to the time it finishes) is about 3.7ms, which allows just 1.3ms of the shutter being fully open for the flash to trigger, at a shutter speed of 1/200, before the rear curtain starts moving. I'm assuming that the camera triggers the flash immediately after the front curtain is fully open.

This means that, if my trigger mechanism induces a delay of more than 1.3ms, the rear curtain will have started moving before one or more of the strobes has fired. Although most radio and optical systems don't induce this kind of lag, if you use (as I did) a radio trigger on a master strobe and then optical slaves on the rest, the lag is compounded, and I occasionally found I was getting the black bars at 1/200 shutter speed. The weird thing is that it is not consistent and I have no explanation for that. I can fix the problem by using all radio triggers or dropping the shutter speed down to 1/160 or slower.

By the way, the significance of me mentioning the flash duration for my strobes is that, when using the shutter speeds close to your sync speed and if your strobe has a long duration - some have up to 1/500s or more, it is almost certain that the rear curtain will start closing before the strobe has finished firing. Instinctively, I would expect this to cause somewhat graded exposure across the image. My strobes have a fairly fast flash duration and I haven't noticed this effect but has anyone run across this?

This was of some interest to me because I have been getting the horizontal bars, so I did a lot of research and some testing. My camera has a nominal sync speed of 1/200 and I am using Britek PS-200 and PS-250 strobes which have a flash duration of 1/1500s. My interest was because I noticed a significant difference when firing just one strobe with a radio trigger and using the built-in optical slaves on the others against having radio receivers on all of the strobes.

I did some testing and worked out that my curtain speed (the time from the curtain starting its travel to the time it finishes) is about 3.7ms, which allows just 1.3ms of the shutter being fully open for the flash to trigger, at a shutter speed of 1/200, before the rear curtain starts moving. I'm assuming that the camera triggers the flash immediately after the front curtain is fully open.

This means that, if my trigger mechanism induces a delay of more than 1.3ms, the rear curtain will have started moving before one or more of the strobes has fired. Although most radio and optical systems don't induce this kind of lag, if you use (as I did) a radio trigger on a master strobe and then optical slaves on the rest, the lag is compounded, and I occasionally found I was getting the black bars at 1/200 shutter speed. The weird thing is that it is not consistent and I have no explanation for that. I can fix the problem by using all radio triggers or dropping the shutter speed down to 1/160 or slower.

By the way, the significance of me mentioning the flash duration for my strobes is that, when using the shutter speeds close to your sync speed and if your strobe has a long duration - some have up to 1/500s or more - it is almost certain that the rear curtain will start closing before the strobe has finished firing. Instinctively, I would expect this to cause somewhat graded exposure across the image. My strobes have a fairly fast flash duration and I haven't noticed this effect but has anyone run across this?

This was of some interest to me because I have been getting the horizontal bars, so I did a lot of research and some testing. My camera has a nominal sync speed of 1/200 and I am using Britek PS-200 and PS-250 strobes which have a flash duration of 1/1500s. My interest was because I noticed a significant difference when firing just one strobe with a radio trigger and using the built-in optical slaves on the others against having radio receivers on all of the strobes. This was of some interest to me because I have been getting the horizontal bars, so I did a lot of research and some testing. My camera has a nominal sync speed of 1/200 and I am using Britek PS-200 and PS-250 strobes which have a flash duration of 1/1500s. My interest was because I noticed a significant difference when firing just one strobe with a radio trigger and using the built-in optical slaves on the others against having radio receivers on all of the strobes. I did some testing and worked out that my curtain speed (the time from the curtain starting its travel to the time it finishes) is about 3.7ms, which allows just 1.3ms of the shutter being fully open for the flash to trigger, at a shutter speed of 1/200, before the rear curtain starts moving. I'm assuming that the camera triggers the flash immediately after the front curtain is fully open. This means that, if my trigger mechanism induces a delay of more than 1.3ms, the rear curtain will have started moving before one or more of the strobes has fired. Although most radio and optical systems don't induce this kind of lag, if you use (as I did) a radio trigger on a master strobe and then optical slaves on the rest, the lag is compounded, and I occasionally found I was getting the black bars at 1/200 shutter speed. The weird thing is that it is not consistent and I have no explanation for that. I can fix the problem by using all radio triggers or dropping the shutter speed down to 1/160 or slower.

This was of some interest to me because I have been getting the horizontal bars, so I did a lot of research and some testing. My camera has a nominal sync speed of 1/200 and I am using Britek PS-200 and PS-250 strobes which have a flash duration of 1/1500s. My interest was because I noticed a significant difference when firing just one strobe with a radio trigger and using the built-in optical slaves on the others against having radio receivers on all of the strobes. 

This was of some interest to me because I have been getting the horizontal bars, so I did a lot of research and some testing. My camera has a nominal sync speed of 1/200 and I am using Britek PS-200 and PS-250 strobes which have a flash duration of 1/1500s. My interest was because I noticed a significant difference when firing just one strobe with a radio trigger and using the built-in optical slaves on the others against having radio receivers on all of the strobes. I did some testing and worked out that my curtain speed (the time from the curtain starting its travel to the time it finishes) is about 3.7ms, which allows just 1.3ms of the shutter being fully open for the flash to trigger, at a shutter speed of 1/200, before the rear curtain starts moving. I'm assuming that the camera triggers the flash immediately after the front curtain is fully open. 

This means that, if my trigger mechanism induces a delay of more than 1.3ms, the rear curtain will have started moving before one or more of the strobes has fired. Although most radio and optical systems don't induce this kind of lag, if you use (as I did) a radio trigger on a master strobe and then optical slaves on the rest, the lag is compounded, and I occasionally found I was getting the black bars at 1/200 shutter speed. The weird thing is that it is not consistent and I have no explanation for that. I can fix the problem by using all radio triggers or dropping the shutter speed down to 1/160 or slower.

By the way, the significance of me mentioning the flash duration for my strobes is that, when using the shutter speeds close to your sync speed and if your strobe has a long duration - some have up to 1/500s or more, it is almost certain that the rear curtain will start closing before the strobe has finished firing. Instinctively, I would expect this to cause somewhat graded exposure across the image. My strobes have a fairly fast flash duration and I haven't noticed this effect but has anyone run across this?

This was of some interest to me because I have been getting the horizontal bars, so I did a lot of research and some testing.

  My camera has a nominal sync speed of 1/200 and I am using Britek PS-200 and PS-250 strobes which have a flash duration of 1/1500s. My interest was because I noticed a significant difference when firing just one strobe with a radio trigger and using the built-in optical slaves on the others against having radio receivers on all of the strobes. This was of some interest to me because I have been getting the horizontal bars, so I did a lot of research and some testing.

  I did some testing and worked out that my curtain speed (the time from the curtain starting its travel to the time it finishes) is 1/300s, which allows just 1/600s of the shutter being fully open for the flash to trigger and complete its cycle. I'm assuming that the camera triggers the flash immediately after the front curtain is fully open. If you take into account the lag on the wireless trigger, say about 1ms, and using the rated shutter speed of 1/200, the radio-triggered triggered flash will have just completed its cycle when the second curtain starts to move.

This means that however fast the optical slave triggers are, even if they respond within 60 microseconds (as Carl suggests above) you will get unequal exposure because the second curtain has started to close before the rest of the strobes have finished their cycle. The problem is that using a mixed trigger system induces a lag that is the sum of each type.

As a result, my recommendation would be not to mix radio and optical triggers if you are trying to get the fastest shutter speed you can out of your system. All radio or all optical. As an aside, the bigger, more powerful strobes usually have a longer flash duration - up to 1/500s or longer - which would theoretically make the problem worse, although I don't have any so I haven't been able to test this.

This was of some interest to me because I have been getting the horizontal bars, so I did a lot of research and some testing. My camera has a nominal sync speed of 1/200 and I am using Britek PS-200 and PS-250 strobes which have a flash duration of 1/1500s. My interest was because I noticed a significant difference when firing just one strobe with a radio trigger and using the built-in optical slaves on the others against having radio receivers on all of the strobes. This was of some interest to me because I have been getting the horizontal bars, so I did a lot of research and some testing. My camera has a nominal sync speed of 1/200 and I am using Britek PS-200 and PS-250 strobes which have a flash duration of 1/1500s. My interest was because I noticed a significant difference when firing just one strobe with a radio trigger and using the built-in optical slaves on the others against having radio receivers on all of the strobes. I did some testing and worked out that my curtain speed (the time from the curtain starting its travel to the time it finishes) is about 3.7ms, which allows just 1.3ms of the shutter being fully open for the flash to trigger, at a shutter speed of 1/200, before the rear curtain starts moving. I'm assuming that the camera triggers the flash immediately after the front curtain is fully open. This means that, if my trigger mechanism induces a delay of more than 1.3ms, the rear curtain will have started moving before one or more of the strobes has fired. Although most radio and optical systems don't induce this kind of lag, if you use (as I did) a radio trigger on a master strobe and then optical slaves on the rest, the lag is compounded, and I occasionally found I was getting the black bars at 1/200 shutter speed. The weird thing is that it is not consistent and I have no explanation for that. I can fix the problem by using all radio triggers or dropping the shutter speed down to 1/160 or slower.