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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Frame split defect with strobe light

The simple fix, as far as I understand, is to shoot 360degree shutter at 48fps in 2K.
 
it seems like this should happen on film cameras too. Am I missing something?
 
Club Strobes

Club Strobes

And it would be scary to get this type of effect in a club. where we shoot tons of strobes and we can't sync them to the camera
 
yes the same thing can happen in film but it causes a much more organic effect. As far as anything else goes though, if you are shooting strobes there are a number of things that can be done to reduce the effect 360 shutter being one of them, higher frame rates another, and genlock synced strobes third. I'm not terribbly worried about this issue. It just causes the DP to have to know this. Also it worries me slightly that anyone who is in the market for a red is questioning whether film can have the same effect, guys this is a dcinema camera not a weekend toy.
 
Jeff Brue said:
Also it worries me slightly that anyone who is in the market for a red is questioning whether film can have the same effect, guys this is a dcinema camera not a weekend toy.
Click to expand...

Jeff welcome to the world of red user full of some future owners with no real knowledge or experience but full of arguments like "well it should work this way because that would be cool".
 
Finner said:
Yes I have, have you??? When I work with 10k lamps they are HMI's so if you have any experience at all with an HMI light you would understand that they have no bearing what so ever on this problem.
Click to expand...

Sorry Finner, I knew exactly what Khmuse was talking about. I guess if I said to kill the baby and the blonde you would not confuse them with the redhead. A 10K could take 5 seconds to go from full on to full off.

10K Mole:
4371-L.gif
 
Dude you killed a baby and a blonde? That confession may be admissible in court. You should watch what you say.

By the way Kevin and I are buddies that go way back and were just screwing around.
 
Well, "way back" might be a just a bit of an exaggeration! :biggrin:
 
khmuse said:
Really, this isn't anything to be concerned about except for some very specific situations. The situations that would cause any effect at all are not unique to the RED, its just the nature of any shutter (electronic or mechanical).
Click to expand...

Not the nature of a butterfly or 180 shutter on film camera or video camera or digital SLR or phantom camera or Dalsa.
 
ibloom said:
Hey I did a little research and wrote this article trying to explain how rolling shutter artifacts occur. I'm going to continue to expand it and rewrite it, but I'd love your comments.

http://www.redhax.net/wiki/Understanding_the_Rolling_Shutter_Artifacts

Cheers,
IBloom
Click to expand...

Ahh! Great explanation, I now finally understand what is going on.

But I didn´t get, in the last part of your article : "A 360 degree shutter does not eliminate rolling shutter artifacts but instead splits them evenly between consecutive frames."

Does that mean that the split will be visible in two frames? Or that it will be in the center of one frame?

The illustrations are great, but an image of a video showing the artifacts mentioned would be greatly appreciated.
 
coboman said:
Ahh! Great explanation, I now finally understand what is going on.

But I didn´t get, in the last part of your article : "A 360 degree shutter does not eliminate rolling shutter artifacts but instead splits them evenly between consecutive frames."

Does that mean that the split will be visible in two frames? Or that it will be in the center of one frame?

The illustrations are great, but an image of a video showing the artifacts mentioned would be greatly appreciated.
Click to expand...
What he means is that the split COULD appear on two successive frames. If the scan is continous (a 360 shutter), the flash (which is asynchronous) could occur just as the scan is completing one frame and wrapping around to the next.

In fact the split doesn't need a flash to occur. It could happen with an instant-on/off light of any kind that is not synchonous. (Tungsten wouldn't do it - too slow to heat up/cool down.) The change would show up most likely in mid-frame and extend as long as the instant-on/off light was in the new state (on or off) then occur again when it swapped states again. Strobes are, effectively, instant-on/off sources of short duration and are fairly common. So you're more likely to see this effect with strobes.
 
jbeale said:
I'd like to suggest instead of "electricity particles" you say just "electrical charge". Particles brings to mind lint or dust or something.
Click to expand...
What, as in the huge lint accelerator at CERN?
 
jbeale said:
I'd like to suggest instead of "electricity particles" you say just "electrical charge". Particles brings to mind lint or dust or something.
Click to expand...

It's a wiki, so please help me rewrite it by clicking on the edit tab above.

http://www.redhax.net/wiki/Understanding_Rolling_Shutter_Artifacts

The 360 shutter will split the flash evenly between consecutive frames if it occurs during readout of the chip. Using a 360 shutter does not reduce the probability of catching a shutter artifact since to my knowledge, readout time is fixed. 360 degree shutter does increase the chances of seeing the strobe though, artifact or not.

Interestingly you may be less likely to catch a strobe in 2K Windowed mode, since readout time will likely be one quarter the time of 4K. This might be helpful if you are encountering uncontrolled flashbulbs at some kind of red carpet event etc.

IBloom
 
ibloom said:
Hey one more diagram you might enjoy at the bottom.
Click to expand...

Perfect. That is now crystal clear.

I have one more question, though. In milliseconds (or fraction of a second -- 1/250, 1/500, etc.), how much time does it take for the mysterium sensor to do the whole scan?

Knowing that number could help make educated guesses of what kind of events would cause the artifacts to appear.
 
coboman said:
Perfect. That is now crystal clear.

I have one more question, though. In milliseconds, how much time does it take for the mysterium sensor to do the whole scan?

Knowing that number could help make educated guesses of what kind of events would cause the artifacts to appear.
Click to expand...

I think that's a question for Rob. I'd like to know the answer myself.

Ian
 
I have never seen a 10k HMI... only 12k...

strobes that fire 50ms long... 50/1000=5/100= 1/20 still not long enough(is my math right?)

So couple things ... Just shot a music video with Lightning strike and 5k Strobes...
Had issues at 180 degree shutter, 1/60 shutter and 360 degree shutter...
at 360 the frame spliting Issue was lessed yet the effect was odd some times almost a double flash effect.
at 1/48th and 1/60 had soffer issue that looked different then the split frame issue...

shooting 360 degree shutter at 48fps didn't seem to help. but had to try. 120fps had other issues sice I had a mix of Flicker free and non-flicker free ballasts on my HMIs... interesting that at 120 fps I had "windows" of opertunaty where everything worked great... and then sections completely unseable...but the window was long enough to get the shot.

VP

www.vincentpascoe.com
 
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