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class="style16"> 12fps - What Shutter Angle

class="Paragraph">Published : 15th January 2009

class="Paragraph">Hello all,

class="Paragraph">I have a shot to do where it will take the camera movement/shot duration about 20 seconds from start to end of shot. This is for a 10 second on air(TV...pal) shot.

My question is at say 12fps what shutter angle can you suggest so that when the footage is ramped back to 25fps it retains a look of realism without too much blur or strobe or is there an alternative more effective way to achieve this?

That is so it 'looks' like a 10 second shot done at 25fps originally.

The shot is a crane/hothead shot from wide in through a doorway up to a plant.
(there are no actors, or any sort of movement in the frame, shooting on a 435)

class="Paragraph">regards

class="Paragraph">David Paul
DoP
Wellington,
New Zealand


class="Paragraph">Actually, if you are going to shoot at 12 fps and play back at 24 fps, (which means you want the screen time move to be twice as fast as you are shooting) then you should leave the shutter at 180 degrees to get the same amount of motion blur as you would get moving twice as fast while cranking twice as fast.

class="Paragraph">Think of it this way...at whatever speed you do the move, if you slow the camera down the same percentage as you are slowing the move down when shooting it, the camera will move the exact same distance while the shutter is open...which means the motion blur will be appropriate at any speed as long as the relationship between the dolly speed and the camera speed is maintained.

class="Paragraph">Mark Weingartner
VFX Photography & Supervision
LA based


class="Paragraph">Mark Weingartner wrote :

class="Paragraph">>>Actually, if you are going to shoot at 12 fps and play back at 24fps, (which means you want the >>screen time move to be twice as fast as you are shooting) then you should leave the shutter at 180 >>degrees to get the same amount of motion blur as you would get moving twice as fast while >>cranking twice as fast.

class="Paragraph">I think when shooting 12fps at 180 shutter, each frame gets exposed 1/24 of a second instead of 1/48 (making the motion blur twice as big as when shooting "normal" 24fps). If "this" is what you want, go for it! Otherwise, if you only want a faster frame rate with "normal look" set the shutter at 90 degrees (for a 1/48 second exposure). That's what I would do anyway.

class="Paragraph">Further; if you were to shoot say 3fps (at 180) you would burn each frame at 1/6 of a second. To get the "normal" look, I would close the shutter to 22.5 degrees therefore exposing each frame at 1/48 of a second.

class="Paragraph">Regards,
Dan Diaconu
Film/video gear designer
Vancouver, BC.

class="Paragraph">604-780-1818
www.dandiaconu.com


class="Paragraph" >>I think when shooting 12fps at 180 shutter, each frame gets exposed 1/24 of a second instead of >>1/48 (making the motion blur twice as big as when shooting "normal" 24fps).

class="Paragraph">It depends a whole lot on what your intention is. I may be misunderstanding the original post, but if the reason the DP wants to under crank is to avoid technical problems with moving at the full speed of the shot, and if, as the original poster stated, there are no actors or moving objects in the shot but only architecture, then I have to disagree with you. We shoot an awful lot of miniatures at very slow frame rates with motion control...this is\ so-called "go motion" where the camera keeps moving on the rig while shooting at a slow frame rate. motion blur is not just a function of shutter speed (that is to say not just a function of length of exposure.) It is a function of movement speed coupled with exposure time.

class="Paragraph">Take a lock-off as an extreme case - no movement at all. In a lock-off, there is no motion blur (assuming, again, no actors, but only architecture) even with one second exposures.

class="Paragraph">Now, let's take a case where you want to move 24 feet in a second...that is the finished shot is, let's say, 48 frames during which time the camera has moved 48 feet. For the purposes of this exercise, we will assume that we are cutting in and out of a moving shot to avoid the secondary discussion of ramp speeds.

class="Paragraph">If you shoot at 24 frames with a 180 shutter, each exposure will encompass a linear move of half a foot, with the camera moving another half a foot while the shutter is closed.

class="Paragraph">Now, let's say that the dolly can't be pushed at 24 feet/sec (which is actually pretty @#$%^& fast...16 mph)

class="Paragraph">In order to get the same look while moving at human speeds, let's say we push the dolly at 4 mph (6 ft/sec)

class="Paragraph">If we crank the camera at 6 frames per second with a 180 shutter, we will discover that we have moved 1/2 foot with the shutter open and 1/2 foot with
the shutter closed. When projected at 24 frames per second, it will look the same as the 24fps shot moving at 24 ft/sec.

class="Paragraph">This is not just a theory - we do it all the time.

class="Paragraph">If, as has been suggested, you skinny the shutter down, you will get less motion blur than you would have with the full-scale move. This may be a great look, and it may even be what you want, but it will not be the same as if you had shot moving at 24 fps with a 180 shutter.

class="Paragraph">Mark Weingartner
LA based VFX DP/Supervisor


class="Paragraph">Dan D wrote:

class="Paragraph">>>"I think when shooting 12fps at 180 shutter, each frame gets exposed 1/24 of a second instead of >>1/48 (making the motion blur twice as big as when shooting "normal" 24fps). If "this" is what you >>want, go for it! Otherwise, if you only want a faster frame rate with "normal look" set the shutter at 90 >>degrees (for a 1/48 second exposure). That's what I would do anyway."

class="Paragraph">Cutting the speed of the camera move (remember, the camera is the only moving thing in the shot, no actors) in half, and cutting the frame rate in half, means that, as Mark suggests, you want to keep the shutter wide open to get the same look as shooting at 24 fps and moving the camera twice as fast.

class="Paragraph">Reducing the shutter angle will reduce motion blur to a greater degree than a 180 degree shutter at 24 fps -- if you want narrow-shutter-angle strobing, it will work, but I don't think that's what they wanted.

class="Paragraph">Jeff "signing because I'm supposed to" Kreines


class="Paragraph">Both techniques will work equally well and is just a matter of achieving the desired results. We have advocated them both and I am sure, he will know by now what to choose accordingly.

class="Paragraph">PS. In all honesty, if I was to shoot the same thing say 1f every 10 seconds for 24fps playback, I would not expose each frame for 5 seconds while the dolly moves. Exposing each frame at 1/48 (regardless the dolly speed or undercrank) will render the "normal" motion blur on each frame when played back (at 24fps or any other speed) but... I guess is just me;-).

class="Paragraph">Regards,
Dan Diaconu
Film/video gear designer
Vancouver, BC.


class="Paragraph">Dan Diaconu wrote :

>>Exposing each frame at 1/48 (regardless the dolly speed or undercrank) will render the "normal" >>motion blur on each frame when played back (at 24fps or any other speed) but... I guess is just me.

class="Paragraph">Dan,

class="Paragraph">Normal motion blur is with the shutter open for half the motion. Go Motion has been a function of motion control rigs for over 25 years.

class="Paragraph">Do you know of any cameras capable of exposing a single frame for 1/48?

class="Paragraph">Stephen Williams DP
EU Based currently in Zurich

class="Paragraph">www.stephenw.com


class="Paragraph">Hi,

class="Paragraph">If you use 90° shutter angle and 12,5 f.p.s. you will get the same shutter time as with 25 f.p.s. 180° shutter. This give you the same unsharpness in movements.

class="Paragraph">Hans Hansson,FSF
Sweden


class="Paragraph">Stephen Williams wrote:

class="Paragraph">>>Do you know of any cameras capable of exposing a single frame for 1/48?

class="Paragraph">The 435 w/ capping shutter/intervalometer can-

class="Paragraph">John Babl
DP
Miami


class="Paragraph">Stephen Williams wrote:

class="Paragraph">>> Do you know of any cameras capable of exposing a single frame for 1/48?

class="Paragraph">Mitchell NC with a Norris controller.
--
Steven Gladstone
New York Based Cinematographer
Gladstone Films
www.gladstonefilms.com
917-886-5858


class="Paragraph">Steven Gladstone wrote :

class="Paragraph">>>Mitchell NC with a Norris controller.

class="Paragraph">John Babl wrote :

class="Paragraph">>>The 435 w/ capping shutter/intervalometer can-

class="Paragraph">Hi Steven & John,

class="Paragraph">Have you been able to shoot 1/48 stop motion without any flicker issues?

class="Paragraph">The IMC 3565 had this option, however the capping shutter built in on the Fries Mitchell had a tendency to bounce. It would work fine for a test but as one rolled & tilted the camera gravity would have an effect.

class="Paragraph">Stephen Williams DP
EU based


class="Paragraph">Sorry, Dan, but it is just you.

class="Paragraph">This is not idle conjecture on my part, we have shot a LOT of under cranked material, from rear-projection background plates to miniatures, to helicopter footage...

class="Paragraph">If you are shooting at the same percentage driving(dollying) speed as you are undercranking, you should use the same shutter angle as you would have wanted to shoot if you were shooting at full movement speed at full camera speed. This is not a matter of aesthetics, it is a matter of physics and math,

class="Paragraph">Motion blur is not just a function of shutter angle, it is also a function of "motion" - it is in the name.

class="Paragraph">If you shoot a move at half speed while cranking the camera at half speed and you skinny the shutter down to 90 degrees, when you speed the footage up to full speed, you will have less motion blur and more strobing than if you
shot it correctly.

class="Paragraph">This might be a REALLY COOL look!!!!! But it is emphatically not a naturalistic one.

class="Paragraph">If you are looking for a naturalistic look for something to cut with footage shot at 180 degree shutter, it is NOT the case that both of these methods will work equally well.

class="Paragraph">Mark Weingartner
LA based VFX DP/Supervisor


class="Paragraph" Stephen Williams wrote:

class="Paragraph">>> Normal motion blur is with the shutter open for half the motion.

class="Paragraph">That is correct when the speed is 24fps. If the speed is altered, the "normal" becomes abnormal (imo)

>>Do you know of any cameras capable of exposing a single frame for 1/48?

class="Paragraph">Stephen,

class="Paragraph">If you close the shutter to 90 degrees and shoot 12fps, each frame will be exposed at 1/48.
At 6fps and the shutter at 45 degrees, the exposure is still 1/48 on each frame, 3fps-shutter 22.5 degrees-1/48, aso.

class="Paragraph">Imo, each frame should have the "normal" look (the 1/48 motion blur creates) but be sharp enough to create an recognizable image.

class="Paragraph">If less than that is required, other "means" are more suitable.

class="Paragraph">I can not imagine how a series of blurred "stills" exposed 1/6 (while the dolly moves) will all of a sudden become sharp when projected at 24 fps (if 3fps would be the choice, and 180 selected). The effect could be nice (to emphasis the motion) but not what I understood to be sought after.

class="Paragraph">However, I can only sincerely THANK YOU (big time!) for your question. You gave me an idea (I probably would have not thought of otherwise!). THANK YOU SIR!

Regards,
Dan Diaconu
Film/video gear designer
Vancouver, BC.

class="Paragraph">604-780-1818
www.dandiaconu.com


class="Paragraph">Dan Diaconu write :

class="Paragraph">>>3fps-shutter 22.5 degrees-1/48, aso.

class="Paragraph">Hi Dan,

class="Paragraph">3 fps @ 22.5 degrees will give a far sharper image than 24 fps @ 180.

class="Paragraph">I often shoot with a motion control, it's quite normal to mix passes shot at
totally different speeds, the motion blur is identical.

class="Paragraph">Stephen Williams DoP
EU Based

class="Paragraph">www.stephenw.com


class="Paragraph">Stephen Williams wrote :

class="Paragraph">>>3 fps @ 22.5 degrees will give a far sharper image than 24 fps @ 180

class="Paragraph">Hi Stephen,

class="Paragraph">I guess we should have all established the dolly speed (and distance traveled) for both circumstances (180 and 90 or... latter 22.5 degrees) before sliding on theoretical discussion.

class="Paragraph">I agree a smaller shutter will create a sharper image. However, if dolly is on the move, the image sharpness is very much influenced by both dolly speed and distance to scene (focal lens/aperture, etc)

class="Paragraph">I tried to imagine the shoot and... (for some reason although you clearly stated "dolly") I saw the shoot on an arch dolly. Not your fault, just my imagination! Why? I "saw" a static BG (or actually registering the image in the same spots in the frame) and a relatively blurred close plane rushing in the foreground (imagine looking outside from a train moving at full speed). Again, no relation to your actual shoot, just my visualization of the shoot (to make it work)

class="Paragraph">>> it's quite normal to mix passes shot at totally different speeds, the motion blur is identical

class="Paragraph">Doesn't this contradict your previous statement?

class="Paragraph">I might miss the rest of the discussion (packing for Europe, leaving in two days)

class="Paragraph">I will (for fun) try and shoot a test when I am back. I will post the clip if I do.

class="Paragraph">Regards,
Dan Diaconu
Film/video gear designer
Vancouver, BC.


class="Paragraph">Hi Stephen,

class="Paragraph">I just shot some time-lapse w/ the 435 Advanced/Intervalometer / capping shutter-while I usually favour the 1/4 sec exposure or longer.

class="Paragraph">I did play around with it-the electronic shutter does compensate for short exposure times(it of course goes down to 11.2 degrees) -

class="Paragraph">You can indeed shoot at 1/48 exposure and even much faster values-

class="Paragraph">Best regards,

class="Paragraph">John F. Babl
DP
Miami


class="Paragraph">Stephen Williams wrote:

class="Paragraph">>>Have you been able to shoot 1/48 stop motion without any flicker issues?
>>The IMC 3565 had this option, however the capping shutter built in on the Fries Mitchell had a >>tendency to bounce.

class="Paragraph">Hi Stephen, you sound like the person who wants my IMC 3565 Maintenance manual.

class="Paragraph">Depending on what animation motor you have, would be my guess. I think the Norris moved at a constant speed. Some motors were designed to "Pop" the movement of the camera open, and hold it until the specified time elapsed, then close the shutter. I think Arri does something similar with the 435, Marc Shipmann Muller (Sorry for bad spelling) would know.

class="Paragraph">Worked with Mitchell’s connected to IMC, and also not computerized. No problems. The Mitchell’s connected to the IMC were all Reflexed by pelicle, so the focal plane shutter was in place, no capping shutter needed. Were I worked we had one spinning mirror reflexed Mitchell (done by Fries), which had a small problem where the shutter dragged against the back of the aperture plate, causing every other frame to have an off exposure. Don't recall if we used a capping shutter or not. I found the problem when routinely pulling the aperture plate to clean it, and found what looked like a scribed arc on the back of the pressure plate.

class="Paragraph">Drawing sharpie on the scribe line, and running a few frames, and having the sharpie be worn off confirmed the problem, and when the Cynex test came back from the lab with uneven exposure, the problem was confirmed.

class="Paragraph">Fries did a very quick and nice job fixing the shutter so it didn't drag, once we sent back the camera.

class="Paragraph">Steven Gladstone
New York Based Cinematographer
Gladstone Films
www.gladstonefilms.com
917-886-5858


class="Paragraph">John Babl writes:

class="Paragraph">>>I just shot some time-lapse w/ the 435 Advanced/Intervalometer/capping shutter

class="Paragraph">I think us old mocon hands are frightened by the idea of using a "capping shutter" to determine exposure. I think of them as rather wanky solenoid-driven things useful primarily for winding film without exposing it (for multiple passes, etc.), but totally unsuitable for anything requiring precision. But then, we had cameras driven by stepper motors, which are addressed pulse by pulse, so any amount of dwell could be inserted into an exposure cycle.

class="Paragraph">Tim Sassoon
SFD vfx & creative post
Santa Monica, CA


class="Paragraph">Hi Tim,

class="Paragraph">The 435 w/ this option uses an integrated capping shutter at the gate- it's meant to guarantee that there is no fogging after about 10 second intervals and longer exposures-but, from what I know, for very long exposures and intervals a conventional capping shutter in front of the lens should also be used - In any case, it's a great system w/ a variety of exposure time options and of course you don't have to touch the shutter to make changes since it's electronically variable 11.2-180 degrees.

class="Paragraph">With my Aaton/Cinematography Electronics intervalometer I've gone up to 10 sec intervals without fogging(but this would depend on conditions) I have experimented w/ ramping time lapse by changing the interval in increments by a second after a number of frames(or decreasing the interval if you want to go the other way)-so after let's say every 48 frames you can increase the interval from 2 sec to 3, or keep decreasing from 8 sec to 2 intervals, etc) It can probably be done w/ a Nikon w/ the remote Laptop/ Nikon capture option as well.
W/ the Aaton you can go from time-lapse to 24fps(w/ proper iris adjustment)on the fly, I didn't have time to try this w/ the 435. The LTR has a fixed 1/4 sec exposure, but I've heard some people invert the motor so the film is always exposed(shutter stays open) and the intervalometer controls the exposure time(?)

class="Paragraph">Best,

class="Paragraph">John Babl
DP
Miami


class="Paragraph">John Babl wrote:

class="Paragraph">>>The LTR has a fixed 1/4 sec exposure, but I've heard some people invert the motor so the film is >>always exposed(shutter stays open) and the intervalometer controls the exposure time(?)

class="Paragraph">You can have an electronics mod done to an LTR that allows a much greater range of exposure control, using a camera engineering intervalometer. I think about 3/10 of a second exposure is minimum, and then up to minutes long. IIRC.

class="Paragraph">Camera Engineering U.K. does the mod (which also allows interfacing with an Arri I.C.U. and a Camera engineering speed ramp device,). I don't remember if the Camera Engineering intervalometer has a capping shutter port, but I'm sure they could make one. I haven't needed it, and I'm more worried about light leaing around the throat than past the shutter.

class="Paragraph">Disclaimer, I had my LTR modded by Camera Engineering, and I know them
very well.

class="Paragraph">Steven Gladstone
New York Based Cinematographer
Gladstone Films
www.gladstonefilms.com
917-886-5858


class="Paragraph">Steven Gladstone wrote :

class="Paragraph">>>Hi Stephen, you sound like the person who wants my IMC 3565 Maintenance manual. .....Worked >>with Mitchell’s connected to IMC, and also not computerized. No problems.

class="Paragraph">Hi Steven,

class="Paragraph">I put all my IMC manuals in the garbage a few months ago, after I saw one fail to sell on EBay!

class="Paragraph">Using the IMC, the camera could ramp to 24 fps, then the capping shutter would then open to expose 1 frame, ramp down and rewind the film ready for
frame 2. One of those things that worked perfectly for a test, but would always flicker on multi day shoot! No problems at up to 8 fps.

class="Paragraph">Using a Flair computer with stop motion I have been able to create a 300 degree virtual shutter at 1 FPS, unfortunately the software only allows you to play around at speeds of 1 FPS or slower.

class="Paragraph">Stephen Williams DP
EU based


class="Paragraph">Stephen Williams wrote:

class="Paragraph">>>I put all my IMC manuals in the garbage a few months ago, after I saw one fail to sell on EBay!

class="Paragraph">Well then I guess it is the recycle bin for the manual. It has been a very long time since I worked in animation, but where I worked, we didn't have problems with the internal capping shutter on the camera (if I recall), however the cameras connected to the IMC were all pellicle reflexed, so perhaps the capping shutter was different.

class="Paragraph">Steven Gladstone
New York Based Cinematographer
Gladstone Films
www.gladstonefilms.com
917-886-5858


class="Paragraph">SW

class="Paragraph">>>it's quite normal to mix passes shot at totally different speeds, the motion blur is identical.

class="Paragraph">>>DD?? Doesn't this contradict your previous statement?

class="Paragraph">Dan,

class="Paragraph">I should have said the motion blur caused by the moving camera is identical on motion control passes shot at different camera speeds.

class="Paragraph">Cheers,

class="Paragraph">Stephen Williams DoP
EU based


class="Paragraph">Stephen,

class="Paragraph">I think I know what you are saying... Is just the wording that keeps us...hmmm....."talking"...

class="Paragraph">Stephen Williams :

class="Paragraph">>>I should have said the motion blur caused by the moving camera is identical on motion control >>passes shot at different camera speeds

class="Paragraph">"different camera speeds" meaning fps (I hope)...but... was it at the same shutter or compensating shutter(for the FPS variation)?(lol)

class="Paragraph">Dan-split/a/thread/in/4-Diaconu
Film/video gear designer
Vancouver, BC.


class="Paragraph">Thank You very much for your experienced and informed replies.

class="Paragraph">I went with 180 degree shutter based on the fact I would be slowing the camera move accordingly. So my camera move was a 20 second move at 12.5 fps(for pal TV title shot for a drama series I have shot on dogibeta)which will be ramped to 25fps thus giving a final shot duration of 10 seconds. footage will be transferred today so I will let you know how it turned out. I also did the same shot at 25fps for comparison plus we played a with some 'in camera' ramps from 6fps to 25fps over the duration of the shot. We had the footage so we played a little.

class="Paragraph">Regards

class="Paragraph">David Paul
Director of photography
Wellington
New Zealand.