Wilford Neumann

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.org/wiki/Comparison_of_movie_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 :)

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?

*desperation-for-knowledge-bump*

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.

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?

*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?

Wow... I was way off.

These were my diagram snd explanation references:

http://books.google.com/books?id=HKosIAtCS1QC&pg=PA22&lpg=PA21&ots=2PIJYT1QK1&dq=panavision+focal+plane+shutter&output=html_text&hl=en

http://books.google.com/books?id=jaXWAQAAQBAJ&pg=PA142&lpg=PA142&dq=panavision+single+blade+focal+plane+shutter&source=bl&ots=PINPwPEgEr&sig=mPcKcuN3wUbD-SBFSqoid_rRo_M&hl=en&sa=X&ei=de4mVLavC42RyAT7w4H4DQ&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?

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.