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Author Topic: Do they make a 4 blade shutter for the Christie G35 Alan Gouger Jedi Master Film Handler Posts: 501 From: Bradenton, FL, USA Registered: Jul 2000 posted 05-20-2006 10:34 AM                        Im running a small 8 foot wide screen and have light to spare. Curious if they offer a 4 blade shutter for this projector. I would love to take advantage of the flicker free smoother pans from a 4 blade. Thanks!  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 05-20-2006 10:43 AM                     Pans will not look more flicker free with a faster shutter...that is in the film...the image was shot at 24fps and increasing your projector's shutter flicker frequency will not "pan out." Beyond 72Hz (3-wing) shutter you are not going to fool your eyes/brain any more so going to 96Hz isn't going to get you anything. In fact, when Showscan was developed, the 60Hz rate was chosen after careful studies noted no or little improvement in audience perception at frame rates above 60Hz. What you can do with your extra light is to stop down your lenses to see better detail in the projected image.  |  IP: Logged Alan Gouger Jedi Master Film Handler Posts: 501 From: Bradenton, FL, USA Registered: Jul 2000 posted 05-20-2006 11:08 AM                        quote: Steve Guttag What you can do with your extra light is to stop down your lenses to see better detail in the projected image. Hi Steve. When you say step down I am guessing you mean like an iris added to the surface of the lens or do you mean a different f stop lens. Years ago when I was new to all this (still am, Im just getting back into this again) and would fall victim to anything told to me I would try anything new out of excitement & I had a super simplex and was told private screening rooms used 4 blade shutters so I tried one and lost a lot of light but the image did indeed have less flicker and showed improvement. I guess I should not have brought the term Pans into this as you pointed out the shutter speed cannot help with this. Thanks Steve.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 05-20-2006 11:25 AM                     Also the single blade crhistie shutter does two revolutions per frame and the pull down scyle is masked in 1/2 revolution not 1/4 evolution as in a conventional shutter so a 3 blade would not be easily possible you would have to change the ratio of the shutter shaft speed to change the shutter  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 05-20-2006 11:47 AM                     Another problem with the 4-blade concept is that most shutters are based on around 50% (so nearly 180-degree for single blade or nearly 90-degree for double blade. You have to have that blade size to allow for the pull down of the intermittent...thus if you go to 4-blades, you have essentially a zero opening shutter and yes that would have less flicker. As to stopping down the lens...yes with an iris. ISCO offers studio stop down rings for their PLUS line of lenses and Schneider has their Cinelux Premiers that have an adjustable iris from f/1.7 - f/4  |  IP: Logged Alan Gouger Jedi Master Film Handler Posts: 501 From: Bradenton, FL, USA Registered: Jul 2000 posted 05-20-2006 12:24 PM                        Oops sorry guys I meant 3 blade from a 2 blade I do not have my Christie yet. It arrives this week so I had no idea what shutter design it had other then because it was a full size projector verses my Devry I assumed it had a standard 2 blade. One should not assume. Thanks for all your explanations.  |  IP: Logged Larry Myers Master Film Handler Posts: 371 From: Herndon, VA, USA Registered: Jan 2001 posted 05-20-2006 01:50 PM                 From what I have heard, it seems that flicker can also be a function of light level. Too much light and you get flicker. So lots of light on the screen may not be a good thing. I have done light meter measurements on my screen and I get about 15 foot candles. Although not a whole lot of light vs daylight of 5000 to 6000 foot candles, it's enough to pain the eyes if you have been exposed to total darkness for more then 1/2 hour. With that level, I really don't see much flicker. So I would not judge screen brightness in the daytime. Rather, do it at night after sitting in a rather dark room for at least 15 minutes. As a kid do you remember walking out of the theater on those sunny Saturday afternoons in the summer? I do, ouch with the eyes. Those theater were very dark even with a movie running.  |  IP: Logged Phil Hill I love my cootie bug Posts: 7595 From: Hollywood, CA USA Registered: Mar 2000 posted 05-20-2006 02:26 PM                  quote: Steve Guttag Pans will not look more flicker free with a faster shutter...that is in the film...the image was shot at 24fps and increasing your projector's shutter flicker frequency will not "pan out." Steve is absolutely correct. The lack of smooth pans is due to the camera film rate and shutter angle and is commonly called "skipping." The ONLY way to make pans smoother is to increase the filming rate (fps) and/or the shutter angle in the camera...OR slow down the panning speed.  |  IP: Logged Alan Gouger Jedi Master Film Handler Posts: 501 From: Bradenton, FL, USA Registered: Jul 2000 posted 05-20-2006 02:52 PM                        Speaking of smooth pans and not to take my own thread off topic on the video side this is a popular topic and the demand for the new breed video processors and Digital projectors display 48FPS eliminating the judder associated with the typical 3:2 pull down from converting film to video at 60 frames. Blue Ray players (soon to be released)will output native 24/48 just like D cinema all without flicker of course. Im still hooked on film though which is why Im here:)  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 05-20-2006 03:30 PM                        So if you want to show silent films at their proper frame rates and you have Christie projectors, you're condemed to having a flickery picture, with no option to easily install a 3-blade shutter? That sucks.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 05-20-2006 03:49 PM                     The condemming started with the projector Scott...sorry. Their shutter is too small. They started with the bow-tie shutter but it has notable flicker. If a Simplex or Century looks more like a square wave on an O'scope display, the Christie looked more like a clipped sine wave. By doubling the shutter velocity, they were able to straighten up the rise and fall times. This also helps the current machine achieve better light since the shutter is fully open longer. Remember, the frequency is the same on all accounts, just the rise and fall times change (some have a hard time with this concept). Now, nothing is to stop someone from making a 3-wing Christie shutter...they will need to get their pulley diameters correct if they have a belt drive shutter or just make the 3-wing shutter for a gearbox-shutter Christie (the original P-35).  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 05-20-2006 04:48 PM                     quote: Alan Gouger I do not have my Christie yet. It arrives this week so I had no idea what shutter design it had other then because it was a full size projector verses my Devry I assumed it had a standard 2 blade. One should not assume. Exactly right. Also if yours has the double blade shutter you ought to see if the party that sold it to you will take it back in exchange for a single blade version... There is a HUGE difference in the projected image with the single blade-double speed shutter over the double blade shutter having a noticable flicker problem that you cannot get rid of no matter what. It was the flicker problem that prompted Christie to go single blade double speed shutter in the first place. It is also more efficient! Also, If you have the GP version with the double sided belt the sound will have at least some flutter no matter what.... The older machines with the gear box did not have that problem but they did have the flicker problem. The new Cine X-35 version is good in all aspects though and the basement reader typically tracks at 2's and 3's. Mark  |  IP: Logged

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