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This topic comprises 5 pages: 1 2 3 4 5
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Topic: 3-bladed shutters
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Warren Smyth
Expert Film Handler
Posts: 158
From: Auckland ,New Zealand
Registered: Aug 2003
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posted 01-12-2004 06:03 AM
My gut feeling is that the apparent increased grain is a fuction of higher illumination pushing up the the lower tones to make the particles in the emulsion more visible.
This would also explain the observed decrease in contrast. If you push up the light, the blacks come up and although the whites maybe brighter, the iris in our eyes close to compensate for the extreme brightness. In short, the raising at the bottom end of the scale isn't matched by a perceived raising at the top end. This translates to an apparent reduction in contrast.
Now as I said, there maybe a tendency in 3 bladed situations to allow the image to be brighter for reasons I've given. However, let's assume that this is not so.
As we know, to produce standard illumination on the screen of film, the light output must be higher at the source with a three bladed shutter. It's been suggested double. If we freeze the picture on the screen for a moment in time, a single frame will be much brighter, (double in fact) than normal. It is this image that the brain perceives, with the raised lower tones (and accompanying perceived higher grain) and holds as persistence of vision. It maybe possible that the extra cut off from the 3rd blade is simply doing what our iris does and compresses the extreme brightness of the whites. More likely, that our brain and persistence of vision is doing the trick of limiting the brightness. The result, higher illumination of emulsion particles (grain) on lower tones resulting in more obvious grain to the eye, and lower apparent contrast.
Naturally, it's only a theory but might be worth considering. The fact is, we know very little about that from which we earn our living - persistence of vision.
Another interesting fact, is that we perceive flicker less on an image in the centre of our field of view. We are more sensitive to flicker on the outer edges of our field of view. This means that audiences sitting closer to the screen may notice the flicker more, as the image is also seen by the outer limits of their view.
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Matthew Jaro
Film Handler
Posts: 74
From: Gaithersburg, MD, USA
Registered: Jul 2003
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posted 07-21-2004 09:13 AM
I have three blade shutters on a pair of XLs. My screen is 16.5 feet wide (micro perf). I previously had 2 blade shutters with 800 watts xenon. I upgraded to 1600 watts (Super Lumex). The projection ports are optical glass and the lenses are the latest ISCOs.
1. I can assert that all three blades are the same size.
2. The price is around $500
3. There is absolutely no decrease in contrast. If anything, contrast is better because the picture is sharper.
4. There is less ghosting because the blades are much wider than you need to mask the pulldown.
5. The machine runs better, because the blades are balanced at the factory.
6. I can run 18 foot Lamberts on the screen with absoulutely no flicker. If I run the projectors with no film, there is still no flicker. I can even get a brighter image with no problem if I want to move to a 2000 watt lamp.
7. I can perceive grain in some current release prints. This is because the image is so sharp, I can see every pore on peoples's skin. I would rather have sharpness than fuzzy focusing where you cannot see the grain. Earlier prints are generally sharper, especially IB prints. If you don't want grain, get a junky lens like a Kollmorgen.
8. Mot importantly, there are no motion artifacts. For example, the astute projectionist would notice that in any horizontal pan shot projected with a two blade shutter, there is a stepping effect. I think this is probably due to strobing of the shutter blade with the movement on the frame. The higher flicker rate greatly reduces this problem.
If anyone has adjusted multi-sync computer montitors, they will note that 60 Hz refreseh rate is intolerable and they will raise it. 48 is horrible.
All in all I can think of no reason why one would not use three blade shutters in any venue where there is sufficient light. After all, they are called "Studio Shutters" for a reason.
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