Film-Tech Forum ARCHIVE: Three blade shutters

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Posted by Mark J. Marshall (Member # 1409) on 04-11-2007, 08:23 PM:

I've seen three blade shutters mentioned here before, but I've never personally seen a projector that uses them. Can anyone reveal what projectors use them? Do they come standard, or are they modifications? And what is the point of them?

Thanks.

Posted by John Pytlak (Member # 331) on 04-11-2007, 08:47 PM:

Three blade shutters increase the number of light interruptions (at 24fps) from 48 to 72, greatly reducing the perception of shutter flicker, at a cost of light efficiency.

Most often used in studio situations, or smaller screening rooms, where light efficiency is not the issue it can be on a large screen. Also used for presentation of silent films, which would have intolerable shutter flicker with a two blade shutter at the slower frame rates.

Posted by Monte L Fullmer (Member # 2797) on 04-12-2007, 01:12 PM:

3 wing shutters are a standard for 16mm projectors since they have the two speed motor - for both sound and silent speed films.

... and also a standard for 8mm if the machine is silent only due to the 16fps speed.

Posted by Robert Throop (Member # 61) on 04-12-2007, 01:36 PM:

quote: Monte L Fullmer
3 wing shutters are a standard for 16mm projectors since they have the two speed motor - for both sound and silent speed films.

I think the Kodak Pageant had a centrifugally operated shutter that had 3 blades at silent speed and 2 blades at sound speed.
Bob

Posted by Jeff Taylor (Member # 443) on 04-13-2007, 02:20 PM:

Yes, it was called the "Super 40" shutter. One other 16mm projector had a similar shutter, but can't think of which one.

Posted by Stephen Furley (Member # 1277) on 04-13-2007, 02:30 PM:

Graflex made one, and Bolex made one which could be manually changed from three to two blades while running.

Posted by Monte L Fullmer (Member # 2797) on 04-13-2007, 04:00 PM:

..and your good ol' Bell and Howell's, esp the older 'suitcase' units, had a single blade counterweighted unit-like what the Christie P35 units have, but it swung around twice and on the third swing, the pulldown from the shuttle mechanism would engage..

My Viewlex 16 unit has the good ol 3 wing fixed shutter assembly - and no silent speed option.

I think that Ampros used a barrel shutter arrangement, but was set up as with a larger master blade with the smaller blade opposite of the master.

Posted by Steve Guttag (Member # 268) on 04-13-2007, 07:15 PM:

And Kinoton beats em all...its a 3-wing below 20fps and 2-wing above...done so by their clever intermittent and shutter system in their "E" series projectors. They cheat it by spinning the shutter faster below 20fps such that the same 2-wing shutter will flash the picture 3-times before pull-down. They are not constrained by a mechanical relationship between the shutter and intermittent.

3-wing can even be configured for up to 25fps if desired for screening room applications.

Just remember, when you put a real 3-wing shutter in any projector, you will loose 1/2 the light...thems the math.

Posted by Bruce McGee (Member # 131) on 04-14-2007, 12:14 AM:

Sorry, posted deleted.

Posted by Phillip Grace (Member # 2262) on 04-14-2007, 02:18 AM:

The Siemens 2000 16mm projector had a 2 or 3 blade shutter which was changed manually from outside the projector with the machine stopped. I recall the shutter openings being quite wide even on the 3 blade setting - probably due to the claw pulldown.

Posted by Demetris Thoupis (Member # 833) on 04-14-2007, 03:57 AM:

Kinoton E beats the hell out of projectors! FP30's with EXTREME amount of light and these projectors never get hot. Largest lamp we use is 3K

Posted by Leo Enticknap (Member # 534) on 04-14-2007, 09:01 AM:

quote: Steve Guttag
Just remember, when you put a real 3-wing shutter in any projector, you will loose 1/2 the light...thems the math.

Good point: I've seen many a silent film presented in a venue which has put the three-blade shutter in but not upgraded the lamp output accordingly, thereby causing a very murky picture.

In answer to Mark's question, most projector mechanisms nowadays are supplied with two-blade shutters as standard, with three-blade ones available to order as a separate part.

Posted by William Phillips (Member # 1162) on 04-14-2007, 09:16 AM:

The difference a 3 blade makes is amazing. 1 of my screens has a 3 blade with a 2k lamp. The picture jumps off the screen. Having good lens on the front is a must as well. That screen has ISCO red.