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Shutter angle?


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#1 James Steven Beverly

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Posted 31 December 2006 - 05:17 PM

This may be a very basic question, but I don't know the answer so I thought I'd ask> My cameras both have fixed shutter angles and I was wondering why many 35mm motion picture cameras have a variable shutter angle? What effect does changing the shutter angle have on the image? I suspect it has something to do with motion blur but I could be totally off. Is it simillar to changing the shutter speed on a video camera? Please let me know. Thanks B)
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#2 Jon Kukla

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Posted 31 December 2006 - 05:32 PM

The shutter angle is what controls the shutter speed (along with the fps chosen). The shutter angle divided by 360 x fps to obtain the shutter speed. It can be particularly critical when working with HMIs, for example, which can flicker if the combination of speed, shutter angle, and mains frequency are not in sync. As you have mentioned, tighter shutter angles mean less exposure time per frame, which provides for less motion blur and hence "sharper" detail. You should remember, however, that each time you halve the angle, it costs a stop of light.

Most manual variable shutters will have positions for the common HMI angles (172.8 and 144), as well as the normal 180, 90, 45 sequence. Some older cameras can open as far as 200+ degrees, although most now cannot go further than 180. Most electronic shutters can go down to around 11.2 degrees.
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#3 Daniel Madsen

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Posted 31 December 2006 - 06:05 PM

There are several technical and aesthetic reasons.

Technical

144-degree shutter- used to film a CTR (tube) TV/monitor connected to a 60-hertz power source
150 - used to film at 25fps with lights connected to a 60-hertz power supply.
172.8 - used to film with lights connected to a 50-hertz power supply.



With 144 and 172.8 you can change your fps as long as your exposure time is divisible by 120 and 100 respectively.

Aesthetic

Significantly less than 180 (i.e. 90, 45. etc) will cause any movement to be very choppy but clearly defined. You can experiment with any video camera.

More than 180 will cause motion blur because the film is being advanced though the shutter is till open. This effect can be enhanced further with duel motor cameras.

Edited by Danielle Frankinshten, 31 December 2006 - 06:05 PM.

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#4 timHealy

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Posted 31 December 2006 - 07:08 PM

Taking the shutter angle theory a bit further:

You can shorten the exposure even further than closing down the shutter by using a snycronous strobe light system like Unilux where you can get really great shots of water and juices flowing out of beverage cans, fruit, and shower heads.

best

Tim
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#5 Jonathan Bowerbank

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Posted 31 December 2006 - 08:16 PM

For a good contrast in different shutter angles. Look at the action sequences of "Gladiator", which were shot with an acute shutter angle. Then, watch some of the action sequences in "Apocalypto" which were shot with the shutter completely open at 360 degrees.
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#6 chuck colburn

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Posted 01 January 2007 - 12:24 AM

For a good contrast in different shutter angles. Look at the action sequences of "Gladiator", which were shot with an acute shutter angle. Then, watch some of the action sequences in "Apocalypto" which were shot with the shutter completely open at 360 degrees.


Hello Jonathan,

360 degrees? Wow that sure doesn't leave much time for pull down. Or am I missing something here?

Happy New Year!

Chuck
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#7 David Mullen ASC

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Posted 01 January 2007 - 12:29 AM

360 degrees? Wow that sure doesn't leave much time for pull down. Or am I missing something here?


Yes... that "Apocalypto" was shot with a digital camera with no mechanical shutter, so it can use a "360 degree shutter angle" (i.e. no shutter at all.)
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#8 chuck colburn

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Posted 01 January 2007 - 01:01 AM

[quote name='David Mullen ASC' date='Dec 31 2006, 09:29 PM' post='145456']
Yes... that "Apocalypto" was shot with a digital camera with no mechanical shutter, so it can use a "360 degree shutter angle" (i.e. no shutter at all.)
[/quote

Oops!
I get it now! It was shot with one of those camcorder thingys.

Happy New Year to all,

Chuck
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#9 Nick Mulder

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Posted 01 January 2007 - 01:04 AM

It could be done with two film cameras both at 180deg and 180deg out of phase with an image splitter of some sort - you could even have higher than 360deg shutter angles with similar set-ups
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#10 chuck colburn

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Posted 01 January 2007 - 01:21 AM

It could be done with two film cameras both at 180deg and 180deg out of phase with an image splitter of some sort - you could even have higher than 360deg shutter angles with similar set-ups


This is true Nick. A forty five degree beam splitter or such. You would'nt even need to use any more stock as each camera would be running at half speed. This would compensate for the fifty percent light loss at the beam splitter. Though this would make for jittery pans if the shutter was left wide open. Can't even imagine the horrors in printing what with one image flipped and it certanily gives a new meaning to alternate printing.
:blink:

Must drink faster...

Happy New Year!

Chuck
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#11 David Mullen ASC

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Posted 01 January 2007 - 01:43 AM

I'm not sure it's the same effect as a single 360 degree (1/24th of a second) exposure at 24 fps.

If the two cameras were in-sync but shooting the alternate half of 360 (180 each) you'd have two frames with only a 1/48th exposure each, which isn't the same thing as a 1/24th exposure (not to mention the light loss from the prism)...

...and you'd be combining two sequential images captured at 1/48th of a second each, just with no time gap between the image captures. So I guess the moving object blurred in one part of the frame on the first exposure and then the next area on the following exposure, but I'm not sure combining them in post creates the same thing as a single 1/24th of a second blur, although close. The physical length of the blurred would be the same so maybe it would be the same, but something about the fact that it is still two frames being combined into one makes me feel that it's not quite the same thing as a single frame with twice the exposure time.

But anyway, I'm not sure what the point of such an elaborate 2-camera rig would be since certainly you're not gaining more exposure (due to the 45 degree partial mirror set-up) as you would with a digital camera that could shoot at 24 fps at 1/24th. And flying that beast through a jungle at high speeds would be problematic.
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#12 Gavin Greenwalt

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Posted 01 January 2007 - 05:53 AM

I'm not sure it's the same effect as a single 360 degree (1/24th of a second) exposure at 24 fps.

If the two cameras were in-sync but shooting the alternate half of 360 (180 each) you'd have two frames with only a 1/48th exposure each, which isn't the same thing as a 1/24th exposure (not to mention the light loss from the prism)...


If you scanned both to DPX and then combined them digitaly with a mathematical "add" operator. It would be exactly the same as a 360 shutter. Assuming perfectly synced shutters, no loss a tthe prism, etc etc...

You would need to expose for the 360 degree shutter though, otherwise it would be a stop hot.

Theoretically, if you shot a digital camera with a 360 shutter and combined the frame previous with an add filter (excluding the add from the previous frame to avoid a loop) you could achieve a 720 degree shutter.

Edited by Gavin Greenwalt, 01 January 2007 - 05:55 AM.

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#13 David Venhaus

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Posted 01 January 2007 - 08:49 AM

Along this same thread, I saw a shutter blade that has two, approximately 22 degree openings spaced about 30 degrees apart, so that in one pass, a single frame will be exposed twice. I was wondering if anyone here has used one of these and how it would look or if you knew of any films that used one so that I could see an example. Thnx
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#14 chuck colburn

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Posted 01 January 2007 - 02:27 PM

Along this same thread, I saw a shutter blade that has two, approximately 22 degree openings spaced about 30 degrees apart, so that in one pass, a single frame will be exposed twice. I was wondering if anyone here has used one of these and how it would look or if you knew of any films that used one so that I could see an example. Thnx


Hi David,
Was that a camera shutter? Sounds more like a projector shutter type.

Chuck
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#15 Nick Mulder

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Posted 01 January 2007 - 02:30 PM

I've always wanted to see what a greater than 360deg shutter would look like - perhaps its similar to an audio reverb, but in forward and reverse ...

At each frame you would have a glimpse of the future and yet still be watching a part of the last frame, It would turn into a mess the higher you went, especially with lots of handheld or movement in the picture...

But a nice high contrast or graphical scene locked off with characters moving about, something like Jamiroquai's 'Virtual Insanity' could be interesting with this effect at moments ... Although that video was great and doesn't need touching thank you :rolleyes:

Interesting also is talking about using film to emulate digital/video effects B)
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#16 David Venhaus

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Posted 01 January 2007 - 09:04 PM

Hi David,
Was that a camera shutter? Sounds more like a projector shutter type.

Chuck


Yes, it was a camera shutter, saw it in a set for a B+H Eyemo.
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#17 chuck colburn

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Posted 01 January 2007 - 09:53 PM

Yes, it was a camera shutter, saw it in a set for a B+H Eyemo.


Hi David,

That's interesting. Not quite sure what you mean by "a set". Never saw any film cameras with shutters that divided the expouser into segments. If I remember right the eyemo had a 180 degree fixed shutter opening. Use to convert them to dc drives in the seventies and eighties. Jimmy Beaumonte and I were always fooling with Mike Ferra's crash cameras. Back then you could pick them up all over town for 20-50 bucks. Wish I had stockpiled a hundred or so. Would like to see that eyemo shutter you saw just for my own edification.

Happy new year,

Chuck
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#18 David Venhaus

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Posted 01 January 2007 - 10:30 PM

It was a set of shutter blades in a box labeled to fit an Eyemo, containing about 5 different shutter blades, such as a 90 degree, a 45 degree, etc and the one I mentioned above. Sorry, I don't have a picture. They were not made by B+H, so they were not standard to the camera. Kinda sorry I didn't buy them, just to see what kind of novel effect that one shutter blade would have.

Edited by David A Venhaus, 01 January 2007 - 10:30 PM.

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#19 Zachary Vex

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Posted 01 January 2007 - 10:31 PM

I lost the loop a few times in my old Kodak Model K, and the result (moving film while the shutter was open) must look a little like how it would look to shoot with the shutter removed. I think I read in this forum somewhere about that being done in a feature... anyone remember?
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#20 David Mullen ASC

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Posted 01 January 2007 - 11:37 PM

With film, you need a shutter or else the whole image becomes a big vertical smeary blur because the film is moving through the gate for about half the exposure time.

"Caveman's Valentine", I believe, for a few shots removed the shutter somehow, but put a spinning rain deflector in front of the lens as an out-of-sync wild shutter, creating an image with odd random vertical smearing.
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