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Adjustable shutter option


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#1 stephen defilippi

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Posted 10 January 2007 - 12:01 PM

If I shoot at 48fps and then project/work at 24fps can I get rid of the blur in the image when Im doing pans and the like. Specifically, I was thinking about shooting landscape out of the side of a car or train while traveling at higher speed. Would this help to decrease the blur? My camera doesn't have an adjustable shutter. Its a arri 16st.

Stephen
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#2 Nick Mulder

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Posted 10 January 2007 - 08:01 PM

If I shoot at 48fps and then project/work at 24fps can I get rid of the blur in the image when Im doing pans and the like. Specifically, I was thinking about shooting landscape out of the side of a car or train while traveling at higher speed. Would this help to decrease the blur? My camera doesn't have an adjustable shutter. Its a arri 16st.

Stephen


Yes, your shutter angle will be effectively halved - but if you dont remove every second frame you'll have 2x slow motion also
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#3 David Mullen ASC

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Posted 10 January 2007 - 10:34 PM

Yes, your shutter angle will be effectively halved - but if you dont remove every second frame you'll have 2x slow motion also


But if he does remove every other frame, he's have the effect of shooting at 24 fps with a 90 degree shutter angle and thus get some strobing.

Basically, the best solution would be to travel slower.
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#4 Nick Mulder

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Posted 10 January 2007 - 11:27 PM

But if he does remove every other frame, he's have the effect of shooting at 24 fps with a 90 degree shutter angle and thus get some strobing.

Basically, the best solution would be to travel slower.


I thought that was the effect he was after ?  Or he was at least aware of that side effect ...

Travel slower - yip ok, that gives less blur per frame for that speed, but your stuck with that speed...  So you shoot at 24fps and again remove every second frame (say if you were driving half as fast) to get the speed you require...  But wouldn't the frame removal achieve a strobe effect anyway ? And again we are stuck with the either half as fast or strobe effect ?  

Perhaps I'm not thinking clearly, just woke up from a snooze -_-

Also, is it easy for him to remove every second frame - this can be done at the printing stage ? Or is it going to telecine ?
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#5 David Mullen ASC

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Posted 11 January 2007 - 01:53 AM

It's unclear why he wants less blur, since blur is essential to reducing strobiness -- unless he wants that staccatto, jerky motion of a shortened shutter angle, in which, yes, shooting at 48 fps with a 180 degree shutter and removing every other frame is the same effect as shooting at 24 fps with a 90 degree shutter -- either way, your shutter speed per frame is 1/96th.

Trouble is that (1) it's a waste of film, and (2) you'd have to find some method of removing every other frame, whether digitally or in an optical printer to a dupe neg.
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#6 Nick Mulder

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Posted 11 January 2007 - 02:30 AM

Trouble is that (1) it's a waste of film

off topic slightly...
I've always wanted to try it but have never had the chance to do it for free - but it would be interesting to try the every second frame removal trick but do it twice, the second offset by one frame so you would up with two rolls of the same scene through the same lens but totally different images on film...

You could do it with any factor - 3x then do it three times - 4x and you'd end up with 4 rolls etc...

I'm guessing the more fast movement in frame the more notable the comparison between the two might be...

Just out of interest though, I cant see any practical applications (yet)
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#7 stephen defilippi

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Posted 11 January 2007 - 06:20 PM

It's unclear why he wants less blur, since blur is essential to reducing strobiness -- unless he wants that staccatto, jerky motion of a shortened shutter angle, in which, yes, shooting at 48 fps with a 180 degree shutter and removing every other frame is the same effect as shooting at 24 fps with a 90 degree shutter -- either way, your shutter speed per frame is 1/96th.

Trouble is that (1) it's a waste of film, and (2) you'd have to find some method of removing every other frame, whether digitally or in an optical printer to a dupe neg.



hi and thanks for the input, im trying to get rid of the blur to sharpen the image, mostly. when projected at 24fps, it slows down, looks clear and sharper . . . . and i was hoping would be less nauseating to watch. i wasnt thinking of removing every other frame, that might cause madness. thanks
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#8 Nick Mulder

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Posted 11 January 2007 - 07:31 PM

i wasnt thinking of removing every other frame, that might cause madness. thanks

prob would cost the same or less to hire a adjustable shutter camera for the shot, maybe even buy one, like an old bolex or something.  

Hmmm, does your camera have a single frame mode and is your shot panning over static imagery (ie. not following a car or panning past wind blown trees etc...) ?   If you were patient and careful with exposures (do a test even) you could do it animation style - the sharpness would be extreme... and you'd have gone from vomit to headache...

I think a lot of the odd feel/look that you get from panning is the fact that the projector is projecting each frame twice - the shutter spins 2x the pull down rate, and this causes the jiggyness which the blur which you might think would counteract the effect just makes it stand out that much more
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#9 David Mullen ASC

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Posted 11 January 2007 - 07:51 PM

hi and thanks for the input, im trying to get rid of the blur to sharpen the image, mostly. when projected at 24fps, it slows down, looks clear and sharper . . . .


24 fps is a rather low frame rate for recording motion, barely adequate for creating the illusion of continuous motion. Unfortunately, using a shorter shutter speed reduces the amount of blur in the frame, but a certain amount is needed to help sell the illusion that the motion is continuous, not a series of still frames being flashed in rapid succession. So if there is not enough blur at 24 fps, the result is strobing.

Now shooting at 48 fps will help smooth motion out, especially if projected at 48 fps, but even if projected at 24 fps and allowed to be slow-motion.

But otherwise, if you want normal motion speed at 24 fps, the best way to reduce blur is to move slower, not use a short shutter speed unless you want strobing -- hence why old textbooks mention "safe panning speed" for 24 fps photography.
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