Paul C. Buff, Inc. Technical Forum

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Tue Dec 08, 2009 2:58 pm

Joined: Tue Dec 08, 2009 2:50 pm
Posts: 4

Hi,
I have two AB800's and Two white lightning x1600's I've got a new project where I need to capture people jumping. I was under the impression that the flash duration of the x1600 was sufficiently short but I'm seeing blur in fingers and toes (the fast moving parts of a person). I'm using a canon 5d mk II in an effectively dark studio. I'm shooting at iso 800 at f14 at 1/160th of a second. The x1600's are set at 1/8th power and the ab800 is at 1/4 (ab800 is a hairlight from above). I'm firing with a pocket wizard. The people are on a black background and ambient light is 4 stops under the exposure I have set so it shouldn't be contributing. I even tried with the studio lights off and got the same blur.
Can someone tell me if (and if so how) I will be able to freeze all parts of the jumping people with my existing gear? I'm not able to come up with a combo that works. everything looks great except for the blurred hands and feet.

many thanks
Stella.

p.s. thanks for creating this forum!




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Tue Dec 08, 2009 3:02 pm

Joined: Tue Dec 08, 2009 2:50 pm
Posts: 4

doh! sorry, I just looked at the lights again, I have the Ultra Zap 1600, not the x1600...all else is correct.




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Tue Dec 08, 2009 3:33 pm

Joined: Tue Dec 08, 2009 3:25 pm
Posts: 13

I'm just a beginner :? , so I might not understand these things properly, but I would try to use a higher shutter speed. I have not done any shoots for jumping, but did a few for dancers. My shutter never goes below 250.

PS And I am also very happy that the Bees got their own forum!!! :)




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Tue Dec 08, 2009 3:49 pm

Site Admin
Joined: Tue Dec 08, 2009 10:43 am
Posts: 5266

the fastest flash duration will come from the lights at full power (this is the case with most studio lights). If a lower powered light is hitting a fast moving subject (or part of a subject) then blurring can happen. If you need to freeze action, use full power. If this is too much power, then you will need to use other methods of light reduction, like moving the lights back, using neutral density filters, etc.

Using a faster shutterspeed than the X-sync will yield a black bar in the scene, and will not help with freezing motion (the flash duration is usually many times faster than the sync speed anyway).

I hope this helps!




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Tue Dec 08, 2009 4:01 pm

Joined: Tue Dec 08, 2009 3:39 pm
Posts: 2

The problem is most likely that the ambient light is high enough that your camera can still detect it. Your camera can see about 5 or 6 stops of difference in light. You need to have a bigger difference between your flash and ambient light. Increasing the power of your flash makes the flash duration longer, so don't increase it any more than you have to, or it could become long enough that it will not stop the motion either, but you should be able to increase it some. With modern cameras, the typical sync speed is 200 to 250. Can you increase your shutter speed? This will reduce the ambient light. If you go higher than the sync speed, you will get a black strip on the edge of the frame. If your subject is not very near the edge of the frame, with the ambient light so low, this should not be a problem. When I shoot with strobes, with a dark frame except for my subject, I commonly use a shutter speed of 320, even though my sync speed is 200. That cuts the ambient light by nearly a full stop. Hope this helps!




Last edited by vmaxguy on Tue Dec 08, 2009 4:17 pm, edited 2 times in total.

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Tue Dec 08, 2009 4:08 pm

Joined: Tue Dec 08, 2009 3:25 pm
Posts: 13

Quote:
the fastest flash duration will come from the lights at full power


Quote:
Increasing the power of your flash makes the flash duration longer


Now I'm confused :?




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Tue Dec 08, 2009 4:10 pm

Joined: Tue Dec 08, 2009 3:39 pm
Posts: 2

I was writing my reply when the moderator posted, so I didn't see it before I posted. The moderators post says the strobes fastest flash duration will come from the strobes full power. I thought the shortest flash duration came from the strobes lowest power, so my answer may be wrong. I am not an expert in strobes, but I am guessing the moderator made a mistake.




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Tue Dec 08, 2009 4:57 pm

Site Admin
Joined: Tue Dec 08, 2009 10:43 am
Posts: 5266

excessive ambient light can be an issue. The best way to see is to take a photo without the lights, at the same settings. If you get a completely black frame, then ambient is not an issue.

For smaller speedlite type flashes, the lower the power, the flash duration is shorter.

On most larger studio lights, particularly analog lights, the durations get slower as the power is reduced. Please visit this link for flash duration specifications

http://www.white-lightning.com/x1600.html

(note the UZ1600's and X1600 have identical flash durations. However, the X1600 has a 1/4 power switch that is not present on the UZ1600. You would refer to the "full" and "1/32" specifications)

Our next generation lights will incorporate IGBT control, which will allow faster durations at lower powers.

for more information on flash duration, please visit this link:
http://www.paulcbuff.com/pcb2009/einstein.html#flash




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Tue Dec 08, 2009 8:17 pm

Joined: Tue Dec 08, 2009 7:37 pm
Posts: 9

I've shot basketball with the AB1600's and AB800's.
The T1 flash duration of the 1600's is what I would consider minimum for any action sport.
As Tech support said when you lower the power on your 800 and 1600's your actually increasing your flash duration and increasing the chance of motion blur.
You should set your SS for max sync speed usually 1/250. If you have cybersyncs, 1/320 is doable with the Canon Mark 2N, 3 and 7D.
If your shooting direct obviously you have way to much light than you need, sounds like modifiers and or lens filters are in order, or smaller strobes. Lower ISO?




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Tue Dec 08, 2009 9:02 pm

Joined: Tue Dec 08, 2009 2:50 pm
Posts: 4

Zero, when shooting with strobe only your shutter speed is effectively the flash duration, you control exposure with aperture, adjusting the shutter speed won't matter. on the 5d mkII the sync speed is supposed to be 1/200th. I've found that 9 of 10 times I get a picture of the shutter at 1/200th so 1/160th is effectively the fastest sync speed. I've found that previous canons can go over, the 5d mkII won't let me even work at the advertised sync speed, let alone over.

thanks for the info on full vs reduced power...that is exactly opposite of what I've always known. why is it different than pack systems?

Stella




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