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Panavision Single Blade Focal Plane Shutter

Panavision shutter

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#1 Wilford Neumann

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Posted 27 September 2014 - 10:01 AM

Hello.
I can 't seem to find enough information on the net to understand the way Panavision's single blade focal plane shutter design works.

Doesn't a single blade have to move in reverse in order to shut? If so, how does it shut without creating uneven exposure?
Just how fast can that blade open/close? Is it instantaneous enough that reverse shutting would't matter? I can't imagine this to be the case.

When adjusting "angle" does this alter the speed at which the blade moves in any way? Or is that instead constant, with the difference being a change in how long the blade stays in it 's "open" position?

Perhaps I'm totally misguided and single blade means something other than what I'm thinking?

Thanks.
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#2 Brian Drysdale

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Posted 27 September 2014 - 10:12 AM

I think you maybe getting confused.

 

There is an earlier thread on this I found while looking for some pictures on the subject : http://www.cinematog...showtopic=53877

 

Adjusting angle does just that, it opens or closes the exposing section of the focal plane shutter, which continues to rotate at the same speed.


Edited by Brian Drysdale, 27 September 2014 - 10:15 AM.

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#3 Wilford Neumann

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Posted 27 September 2014 - 12:15 PM

Wow... I was way off.
These were my diagram snd explanation references:
http://books.google....html_text&hl=en
http://books.google....ved=0CCAQ6AEwAQ

So the focal plane shutter is merely an adjustable rotary disc shutter *at* the focal plane instead of slightly in front of it. Is that correct?
And for what, exactly; the sake of a more perfect edge to the start and stop of exposure?
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#4 Wilford Neumann

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Posted 27 September 2014 - 12:37 PM

*Seems I can't edit my post.

Further, that focal plane shutter would also be an adjustable butterfly type to match the reflex mirrors' rotation, correct?
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#5 Mark Dunn

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Posted 27 September 2014 - 12:49 PM

The shutter can't be at the focal plane, of course- it's slightly in front. The term is an approximation.


Edited by Mark Dunn, 27 September 2014 - 12:50 PM.

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#6 Wilford Neumann

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Posted 27 September 2014 - 01:02 PM

Alright. Should've been clear:

So the focal plane shutter is merely an adjustable rotary disc shutter slightly in front of the focal plane instead of "more than 'slightly'" in front of it. Is that correct?
Perhaps, "as close to the focal plane as possible" instead of some general distance in front?
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#7 Simon Wyss

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Posted 28 September 2014 - 01:55 AM

Correct

 

The closer the shutter operates to the aperture, the sharper its edges are projected on the film. Due to that the effective opening angle is somewhat smaller than it actually is. Closer to the focal plane means closer to the physical opening angle. Losses are found between 2 and 5 degrees, depending also on the cone angle of the incident light, in other words less loss with longer focal length lenses and more with wide angle lenses.

 

Among 16mm cameras that distance is 4,5 mm with the Ciné-Kodak Special, 3 mm with the Paillard-Bolex H, still less with the Pathé WEBO M. 35mm cameras have longer spacings.

 

Cameras with a mirror-shutter reflex viewing system intersect the light from the lens at continually increasing distance across the image height (image width with older designs). Purpose-built conical rear lenses reach very close to the shutter but the 45 degrees angle doesn’t disappear.

 

Not the most important feature of a film motion-picture camera but it doesn’t harm to know about.


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#8 Wilford Neumann

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Posted 28 September 2014 - 02:59 PM

Are there any substantial pros and cons to focal plane shutters (with separate reflex mirrors) vs mirror-shutter reflex types? What warrants the 2 different types? While light reaches the film somewhat differently, is there really any d.o.p. concern to be had there? Is actual image sharpness affected? Is having room for a gelatin filter right in front of the film the only real benefit? Is it more of a design concern? Ease of assembly with one vs the other, maybe? Why are there 2 types?

Also, was I correct about Panavision's focal plane shutter having to be butterfly to match the rotation of the seperate reflex mirrors?

Not the most important feature of a film motion-picture camera but it doesnt harm to know about.


=) My interest actually stems from differences in motion rendering between camera systems. I now know to probably pin it down to half moon vs butterfly shutter design, but I want to understand the other elements that I once thought were variables.
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#9 Wilford Neumann

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Posted 01 October 2014 - 01:53 AM

*desperation-for-knowledge-bump*
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#10 Simon Wyss

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Posted 01 October 2014 - 04:22 AM

The shutter has only one influence on image definition, that is by exposure time, often referred to as shutter speed.

 

Whatever system is employed, calculated as section of the cycle, bigger angles let the light impress the film longer. A cycle is given as 360 degrees. So, for example, a film advance mechanism acting over 170 degrees may be hidden behind a 180 degrees shutter blade (with safety margins). Your camera thus records 30 seconds out of 60 seconds life.

 

There are reciprocating shutters in movie cameras: Pathé-Baby (9.5mm film), Camex (9.5 and Double Eight film), Beaulieu (16, 9.5, 8mm formats) or a reciprocating reflex finder mirror (Eclair ACL). As much as I know there’s never been a 35mm movie camera with a Guillotin-type shutter until today.

 

 

The more or less sharp shutter edge shadow on the film is of minor importance. I really only mentioned that for curiosity. The term focal plane shutter is common in photography to designate a concept different from the central or leaf shutter, later it was a New York City promotional thing in the early 1930s. The Paillard-Bolex H cameras had the biggest shutter opening angle of all small-gauge film cameras from 1935 to 1946 when the Mitchell 16 came out.


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#11 Wilford Neumann

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Posted 01 October 2014 - 06:42 AM

I appreciate your replying again! But I fear it's moved away from what I'm questioning.

Let's say we have 2 basic groups of modern rotary shutter design:
One as close to the focal plane as possible, with reflex mirroring on it's own seperate blade(s) somewhere in front of the shutter;
We'll call this "modern focal plane shutter design."

Or one neither as close as possible nor too far from the focal plane with reflex mirroring attached to the front side of the shutter.
We'll call this "modern non-focal plane shutter design."

Since you've established there is negligible difference to the image between designs, why are there 2 of them? What could be the motive behind designing a second type? Why do 2 types exist?
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#12 Dom Jaeger

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Posted 01 October 2014 - 07:30 AM

Are there any substantial pros and cons to focal plane shutters (with separate reflex mirrors) vs mirror-shutter reflex types? What warrants the 2 different types? While light reaches the film somewhat differently, is there really any d.o.p. concern to be had there? Is actual image sharpness affected? Is having room for a gelatin filter right in front of the film the only real benefit? Is it more of a design concern? Ease of assembly with one vs the other, maybe? Why are there 2 types?
Also, was I correct about Panavision's focal plane shutter having to be butterfly to match the rotation of the seperate reflex mirrors?


One of the primary advantages of a focal plane shutter is that light cannot leak or reflect past it on to the film, as can happen with angled mirror shutters, and particularly the butterfly type. This tends to be more of an issue when there is a longer duration involved, such as with time-lapse, stop-motion/animation or between takes. Arriflexes, for example, ideally need capping shutters for time-lapse or animation, which cover the gate just in front of the focal plane between exposures.

It's been a long time since I worked on Panavision cameras but from memory the focal plane shutter is a variable half-moon, not a butterfly. PV cameras evolved from Mitchells, which had half-moon focal plane shutters before pellicles and mirrors were added to make them reflex.

By contrast, Arri invented the angled mirror shutter, and apparently never felt the need to include an additional focal plane shutter in their cameras. Their design (particularly the later half-moon mirror shutters) works perfectly well for most applications, and capping shutters were available for the few applications where it might be less than perfect.
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#13 Simon Wyss

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Posted 01 October 2014 - 09:04 AM

What could be the motive behind designing a second type? Why do 2 types exist?

 

Ahm, more than two types do actually exist, dozens of them. It depends on the design of a particular camera. If we look at a precursor, Le Prince’s 1888 camera, we have already a near focal plane shutter, an adjustable one even.

 

The Smith camera of 1897 has a drum shutter, the drum surrounding the entire mechanism and the film spools. Akeley picked up that idea for his wildlife camera, patented 1915. The third such apparatus was the 1924 KINARRI. A little drum shutter between lens and film can be found with a number of 16mm film cams. It’s about available space after the gear train has been set. To complete the picture, conical shutters have also been devised, for instance in the Debrie Sept of 1921.

 

Like Dom said, the Panavision cameras are derived from the Mitchell line. The Mitchell Standard, in turn, is based on the patented Leonard camera which again was a response to the then predominant Bell & Howell model 2709. The reflex shutter camera came only in 1937 when the professional studio camera had already led an eventful life. To help you understand a little what the engineers deal with: The closer one can bring the shutter to the film, the smaller it can be made. Yet there must be an aperture plate, material to hold it, space for a ground glass mount, and other mechanical parts.

 

I am tempted to say that any real mechanical-optical progress in film motion-picture cameras has not been made since the 1946-47 Caméflex or Camerette that has the vertically deflecting mirror shutter.


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#14 Wilford Neumann

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Posted 01 October 2014 - 03:33 PM

One of the primary advantages of a focal plane shutter is that light cannot leak or reflect past it on to the film, as can happen with angled mirror shutters, and particularly the butterfly type. This tends to be more of an issue when there is a longer duration involved, such as with time-lapse, stop-motion/animation or between takes. Arriflexes, for example, ideally need capping shutters for time-lapse or animation, which cover the gate just in front of the focal plane between exposures.


I remember reading something about all of this years ago. I can't believe I forgot. Thank you.

It's been a long time since I worked on Panavision cameras but from memory the focal plane shutter is a variable half-moon, not a butterfly. PV cameras evolved from Mitchells, which had half-moon focal plane shutters before pellicles and mirrors were added to make them reflex.


Ha, someone ought to change all this: http://en.wikipedia....e_cameras#35_mm

I'm getting more and more reliable sources saying that their shutters are adjustable halfmoons and not butterflies. So with every half rotation of the reflex mirrors, the shutter would make a full rotation?

By contrast, Arri invented the angled mirror shutter, and apparently never felt the need to include an additional focal plane shutter in their cameras. Their design (particularly the later half-moon mirror shutters) works perfectly well for most applications, and capping shutters were available for the few applications where it might be less than perfect.


Makes sense!

Simon;
Hmm. I understand camera designs of today are based on cameras of the past, if that's what you were trying to explain, but what I was really looking for was why the engineers of our modern workhorses today might have chosen one design in their camera vs another. A shutter that takes up less space? I get that, other complication aspects aside :)
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