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photography: motion blur and flash


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#1 Charlie Wuppermann

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Posted 16 February 2006 - 09:35 AM

hello everyone,

i am experimenting with applying some photograhpy techniques to film. one of these technniques is when a subject in a photograph is sharp but also has a motion blur tail behind it (i think it has been used to some nike adds). I think that this is achieved by using a long exposre and a flash towards the end of this exposure. For exapmple a half of a second exposure and a tenth of a second flash.

Now I am wondering whether this can be applied to film and the moving image as well. I already tried to get motion blur by slowing down the camera and getting a TK done at the same speed (f.e. 8 fps and scan at 8 fps). For example: there is a person running through the frame in motion blur. that was easy to achieve but now I want the movement to become sharp and not blurred for while in the middle. I was thinking about different options. maybe using a flash that is in and out of synch with the shutter of the camera? Or maybe just cranking the camera speed up and down quickly? My brain starts flipping .... anybody any ideas? I guess I have to do some test, or better a lot of tests ....

thank you.
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#2 kata

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Posted 16 February 2006 - 09:44 AM

your best bet would be to do it at post-prod by overlaying frames.

you could try using a high-speed strobe (disco strobe, not photo flash) and low shutter speed, but you wont get a very long trail.
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#3 Jamie Metzger

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Posted 16 February 2006 - 12:38 PM

I can't think off hand how this would work in film, since your frames are passing at 1/48th of a second. In photography, when you want that effect that you were talking about, you flash in the beginning to get that silid image, and then make sure there is enough light bouncing off subject, and for the remainder of the exposure the light reflected off subject will burn into the film.

Seems like a spot meter would help in this situation.
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#4 David Mullen ASC

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Posted 16 February 2006 - 12:59 PM

The only way to get long exposure times per frame is to undercrank, but yes, you could use a strobe light in sync with the shutter to flash the subject in briefer times to reduce their blur. Trick would be to have the background lit with continuous light and the foreground lit with strobes. However, you'd get the choppy motion from shooting at low frame rates (or sped-up motion.)

One advantage to shooting digitally is at least you can double the amount of blur by switching off the shutter, so you wouldn't have to undercrank as much for the same affect. You could shoot at 12 fps and get a 1/12th of a second exposure time per frame, as opposed to have to shoot at 6 fps with a film camera to get 1/12th, since it would have a 180 degree shutter.
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#5 Charlie Wuppermann

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Posted 17 February 2006 - 04:15 AM

thank you
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#6 Jarin Blaschke

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Posted 18 February 2006 - 12:41 AM

If the strobe(s) was the only source of illumination, could you somehow remove the shutter from the film camera? Also - how would you synchronise a strobe to a camera - or at least make it fire exactly every 1/24th of a second?
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#7 David Mullen ASC

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Posted 18 February 2006 - 12:46 AM

If the strobe(s) was the only source of illumination, could you somehow remove the shutter from the film camera? Also - how would you synchronise a strobe to a camera - or at least make it fire exactly every 1/24th of a second?


Well, you could remove the shutter as long as the strobe only fired while the film was static in the gate, not advancing to the next frame -- so you might as well leave in the shutter. You don't really get more usable exposure per frame by removing the shutter since it needs part of the time to move to the next frame.

In terms of syncing strobes to the shutter, there are sync boxes for that but honestly, I've never done strobe photography, only fired strobes randomly (not in sync) during scenes (for nightclub scenes, gunfire scenes, etc.)
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