Film-Tech Forum ARCHIVE: Strong Millenium heat shield/shutter contact

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Posted by Bryan M. Montgomery (Member # 4412) on 10-23-2007, 12:49 AM:

Some of you have probably experienced the ticking, and then the eventual grinding of the heatshield as it contacts the shutter inside the cramped shutter box of the millenium projectors. I've tried many things, including taking bolt cutters last Thurs. to the heat shield to prevent this. Does anyone have any tips or ideas I havent tried?

Posted by Monte L Fullmer (Member # 2797) on 10-23-2007, 03:58 AM:

Take out that front "heat shield" (actually, it's called a light baffle) and your noise will go away and your light will be brighter...

They're all gone out of my Mils and PR-1050's

-Monte

Posted by Ken Lackner (Member # 1002) on 10-23-2007, 06:53 AM:

Would that be safe on the film with the larger lamps?

Posted by Monte L Fullmer (Member # 2797) on 10-23-2007, 01:29 PM:

Hi Ken - I did it at a Drive-In on a PR-1014 with a CFS console behind it having a 4500w bulb inside .. and it did brighten up the imagery some.

And the film temperature coming out of the gate (water cooled) was the same.

The heat comes from from the entire beam, but your main light source from the mirror is actually from the outer edges of the mirror. Thus, the baffles actually cut down some of that edge reflected light causing less light to enter the aperture.

What those two baffles "supposed" to do is to keep the light from "crawling" around the edge of the shutter blades and causing excess flicker, since the blades are so close to the aperture and you don't have the large shutter blade wings like with the older projectors and the Centurys (this is where the early Christie 35 kinda goofed up with that little 'bowtie' shutter blade) that can effectively cut the light, but even then, you still get a little bit of edge "light crawl" with the Centurys.

thx-Monte

Posted by Scott Norwood (Member # 30) on 10-23-2007, 06:23 PM:

Stupid question: why does the size of the shutter matter? The Century shutter is physically larger than the PR-1014 shutter, but I can't tell the difference in image quality on screen (assuming similiar lenses, etc.). Am I missing something?

Posted by Tim Reed (Member # 137) on 10-23-2007, 06:43 PM:

FWIW, the diameter of the shutter has to be large enough to cover the aperture entirely. There were some Century shutters out there in the early 80s that weren't quite large enough around, so the light leaked around the edge of the blade. This manifested itself as a travel ghost that couldn't be eliminated.

Generally speaking, the closer the shutter is to the aperture, the quicker it can blank the light, and the narrower the blades can conceivably be made (not necessarily the diameter, though) - resulting in higher light transmission

Posted by Steve Guttag (Member # 268) on 10-23-2007, 08:14 PM:

Scott,

Shutter diameter translates into shutter velocity (linear) which translates into potential brightness improvements and reduced perceived flicker.

While the angular velocity of a smaller shutter will be the same, the linear velocity is a function of the angular velocity multiplied by the radius of the shutter. A Christie bow-tie shutter is annoying to watch...very flickery as the shutter is almost always closing or opening the light path. With a single wing shutter, the angular velocity is doubled, which is effectively like doubling the radius of a double wing shutter. I forget if the christie blade is 4 or 5 inches in diameter...as such its single wing version performs a little worse than Century's shutter which is nearly 12 inches in diamter (11" and change). Simplex's conical shutter cuts the aperture more evenly than the Century or Christie style. As such, the Simplex has a better chance at a more uniform image illumination.

Steve

Posted by Scott Norwood (Member # 30) on 10-23-2007, 08:39 PM:

Tim and Steve--thanks!

So, the "ideal" machine would have the shutter with the highest linear velocity (all other things being equal)? Where do double-shutter machines fit into this? (Is there such a thing as a double-shutter Simplex, not counting the front-shutter Super and E7 variants?)

Related question: what is it about Kinoton projectors that makes the image look so great? Is it just a steadier movement, or is there some other magic in the shutter design or elsewhere? Unlike Simplex vs. Century, I can definitely tell the difference on screen between Kinoton and everything else...not sure why.

I have never dealt with Christie projectors and can't comment on their image quality. From what I can tell, this is probably a good thing.

Posted by Mark Gulbrandsen (Member # 72) on 10-23-2007, 09:03 PM:

quote: Steve Guttag
Simplex's conical shutter cuts the aperture more evenly than the Century or Christie style. As such, the Simplex has a better chance at a more uniform image illumination.

I don't quite agree with that line. In fact it has do to with both shutter velocity and working distance from the film plane. In the Simplex the shutter is about 1.5" from the film plane... cutting off a bit larger diameter cone of light but the large diameter shutter gives a decent velocity within the aperature opening itself. In the Christie the shutter is about .7" back from the film plane... you could amputate your finger! So being closer the Christie is cutting a smaller cone of light but with a smaller diameter shutter it doesn't have the velocity of the Simplex... thats the main reason Christie stepped it up to double speed with a single blade. With the Christie shutter closer to the film plane than the Simplex and running at double speed it translates to roughly the same velocity as the larger diameter Simplex blade and as a result the Christie has more or less the exact same light efficiency as the Simplex.

Scott,
Christies can put out great images. You have the same basic star and cam that is in the X-L combined with a long curved gate with upper AND lower lateral guide rollers.

Regarding Monte's removal of the inner light shield... The shutter blade is going to be sinking ALOT more heat and the outer shutter bearing isn't going to like that over the long haul!

Mark

Posted by Monte L Fullmer (Member # 2797) on 10-23-2007, 11:48 PM:

Thus, going back to the original question of the light baffle running into the back of the shutter blade - and if one doesn't want to do this mod - is to loosen the shutter blade and to see if it can be pushed back a bit, or loosen up the light baffle bracket screws to see if the baffle can be moved back a bit.

If you got a bouncy shutter blade, then it could be a bearing problem that needs replacing ..

Posted by Mark Gulbrandsen (Member # 72) on 10-24-2007, 09:29 AM:

Monte,

What I do sometimes is to mount that baffle on the back side of the L bracket that it normally mounts to the front of. This affords alot more clearance between it and the shutter blade. If it gets warpped its also a very inexpensive part to replace... less than 20 dollars. I always kep them in the light path!!

Mark

Posted by Monte L Fullmer (Member # 2797) on 10-24-2007, 02:12 PM:

Thx Mark. Yea, found that out the hard way when th two baffle mounting screws came loose and the baffle leaned forward into the shutter and froze the projector up.

Busted up the shutter, and had to replace two vertical shaft gears let alone rebuild the shutter drive assembly...

Posted by Steve Guttag (Member # 268) on 10-24-2007, 05:23 PM:

The shutter distance to the aperture has its ups and downs...while it is cutting a smaller cone of light, it is closer to the focal plane which makes the transition more visble...it make the Christie bow tie shutter all that much more annoying (it really is a horrible thing to sit through, in my opinion).

Mark not agreeing with the method of cutting the aperature aside...it is a fact none the less. The Simplex (conical) shutter will cut the aperture square, or more square, than either Century or Christie's bow-tie. Turn the machines over by hand and look right down the lens receiver at the aperture and see how the various shutters block and unblock the aperture...some do it better than others.

As to Kinoton...their mechanical machines have long since used a single wing largish conicalish shutter (we not so conical but angled...the AA2 shutter has a slight conicalness to it). As such, it is spinning at twice the angular velocity of a standard shutter but due to its larger radius, its linear velocity is also great there. This velocity means for a faster opening/closing off of the light as well as their ability to use a greater than 50% shutter without ghosting.

Their "E" projectors use a bow-tie shutter, angled (except for the FP75) and its velocity varies based on film speed. As such, they don't tend to look identical between a mechanical and a "E" projector. But then again, the "E" projector is notably steadier too so you are going to get a different look there.

Note, the steadiness of the projector does not affect the flicker or brightness, but it does improve image resolution as you eye will see more detail rather than using persistance of vision to morph an unsteady image into a soft appearing one.

Double shutters are another means to increase blade velocity. By adding the second shutter (counter-rotating) you double the linear velocity of the blade. This is most often used to increase light output. By making each blade smaller (less blade, but same radius), you effectively increase the "open" time so that the average light level is increased. The disadvantage to this method is that the center of the image is the last to close and first to open...as such, it will induce a hot-spot. I find they also tend to have a bit of a pulsating light to them as well.

Steve

Posted by Mark Gulbrandsen (Member # 72) on 10-24-2007, 06:56 PM:

Steve,

The bow tie was obsolete well over 10 years ago on the P35GP machine and I don't know of a single one still being used although I do have a box full of them. is I will grant you that the conical is much faster cutoff than the bow tie... but lets compare apples and apples and not mislead everyone here. Compare the now ages old and still current single blade Christie shutter and the Simplex conical shutter and you'll find the cutoff angles almost identical as well as the light efficiency of each.

Also the diameter of the cone of light you are cutting off has as much to do with efficiency as does the distance from the film plane. You can cut a smaller cone of light much faster and be able to use a smaller cutoff blade and so on and so forth... Sorry, I can't get around the laws of physics but if you can please enlightn us on how you do it.

Thanks,
Mark

Posted by Sam D. Chavez (Member # 1841) on 10-24-2007, 07:45 PM:

If anyone were to read this post a few years down the road we will all look mighty silly arguing about this while D-Cinema takes over.

The main advantage of the Simplex is the closeness of the shutter to the film plane. This makes for a more precise light cutoff (I.E. the shadow of the blade is in focus with the film plane) vs. Century and way less chance for stray light to get around the shutter. This is similar in effect to projectors with apertures close to the film plane vs. those further back. The aperture shadow is much fuzzier or the transition from black to white take s more room on a Century vs. an XL?

I doubt even the double speed shutter Christie is as efficient as the XL or the DP70, but as long as we are playing this how many angels can dance of the head of a pin sort of discussion, someone who knows how should do the theoretical and practical efficiency tests.

Posted by Mark Gulbrandsen (Member # 72) on 10-24-2007, 09:44 PM:

The published figure for the DP-70 is 54%. As for the other two its pretty simple and not very confusing although neither projector has an actual published spec... But to get the same efficiency as the Simplex Christie sped their shutter up and it is closer to the film by 50% than the Simplex shutter. Anyone here that can't see what they did to make up the difference is blind as a bat!

Mark

Posted by Sam D. Chavez (Member # 1841) on 10-24-2007, 10:05 PM:

As I remember, this projector had a reputation as a light sponge.

The bronze gearbox also could not stand any heat so the next step in a long line of fixes was to eliminate the gearbox with the twisted belt and essentially the same bow tie shutter with pretty low rotational speed. Somewhere along the way it went to a one wing shutter to improve the output.

All else being equal, the Christie should put out as much light as out beloved DP70, but we know it does not.

Posted by Mark Gulbrandsen (Member # 72) on 10-24-2007, 10:45 PM:

You and Steve seem stuck discussing things that haven't existed in the Christie world for over a decade.

Mark

Posted by Sam D. Chavez (Member # 1841) on 10-24-2007, 11:31 PM:

Like I said, the whole topic is absurd, like who makes the best wagon wheel.

It is very hard to forget a projector that had such humble beginnings and has so much to be humble about.

Posted by Bryan M. Montgomery (Member # 4412) on 10-25-2007, 01:28 AM:

Lose the baffle, or keep it? Is it possible to get a consensus?
I have already moved the baffles to the rear of the L-bracket like you said Mark, and they still make contact at times.
One thing I forgot, I only have this problem with our projectors mated to 3K lamphouses. They are the only fussy ones.

Posted by Monte L Fullmer (Member # 2797) on 10-25-2007, 04:14 AM:

Interesting that you still got 'shutter ping' coming from that moving. Wonder, if that baffle then is warped to where the leading inside edge is so warped that it's pinging the face of the shutter still.

When you took it off, did you have to straighten it some?

Posted by Mark Gulbrandsen (Member # 72) on 10-25-2007, 07:38 AM:

Not only can that baffle warp but so can its mount and the entire back plate that the mount goes onto as well as the shutter housing... humble schumble oei vie! Its not really as common on newer machnes but the plague with the old black ones since none of those castings were heat treated.

Posted by Steve Guttag (Member # 268) on 10-25-2007, 08:15 AM:

Do you have water cooling, by any chance? Those cooling tubes on the Simplex get routed over the intermittent and come VERY close to the shutter.

As to Christie...I've been in a single complex, doing studio screenings and had mix of both shutters.

Mark, you seem to look at the things that interest you and ignore the rest. The Simplex shutter cuts the aperture nearly square...the same can not be said of non-conical shutters, period. While, yes the smaller cone of light that Christie is cutting does go towards their efficientcy, I have yet to find that the single-wing Christie is as light efficient as either the DP70 or the Simplex...but more on the order of Century. However, as the shutter moves closer to the film plane, the shutter also moves into the focal point of the lens and will have a more pronounced flicker to come with it...you can even see it with Simplex as compared to Century...that is Simplex has a pulsation to its image that Century does not.

As to DCinema...sure it is coming in at the moment but it does not negate the issues of film in the present day. I, for one, am still installing mostly film systems with video augmentation.

Steve

Posted by Sam D. Chavez (Member # 1841) on 10-25-2007, 10:33 AM:

I'm not so sure the pulsating is due to the closeness of the shutter to the film. It's there, but why is not proven.

Posted by Monte L Fullmer (Member # 2797) on 10-25-2007, 01:05 PM:

only time I see that pulsation is if the bulb focus is a bit too close ..and the pulsation is really noticable on the end credits.

That tells me to back the bulb up a bit to where the light just begins to dim on the screen.

Posted by Bryan M. Montgomery (Member # 4412) on 10-27-2007, 01:47 AM:

You guys are killing me... [Confused]

Posted by Monte L Fullmer (Member # 2797) on 10-27-2007, 03:33 AM:

[Big Grin]

Welcome to Film-Tech! You get tons of information here.

Posted by Steve Guttag (Member # 268) on 10-27-2007, 08:16 AM:

Sam, I'll conceed there is no study that out and out proves a pulsation that relates the shutter to aperture...however, it certainly passes the "duck test." Find a shutter in close proximity to the aperture and the image will generally have a pulsation. I am rationalizing that the shutter is closer to the focal plane and is therefore being observed opening and closing. I don't see this same thing on Century projectors where the shutter is notably farther away and creates more of a dissolve.

Monte, the pulsation we are referring to is not the same as an over focused lamp...every Simplex XL or later exhibits it (as to Christies). It is most easily perceived on end credits (white letters on black backgrounds). Haven't you ever played "name the equipment?" Go into a theatre you are unfamiliar with to watch a movie and predict what they are using by just using your eyes and ears watching the movie...after the show...see if you were correct. Some projectors have "tells" and Simplex, Christie and Century definately have them. Likewise with speakers...they may look alike on an analyzer after tuning but I can tell you when I'm hearing an EV DH1 compression driver rather quickly. Likewise with the various digitals...I still find it unsettling that I like the sound of SDDS the best overall.

Steve

Posted by Mark Gulbrandsen (Member # 72) on 10-27-2007, 09:34 AM:

quote: Steve Guttag
Mark, you seem to look at the things that interest you and ignore the rest.

Steve, Thats hardly the case... If you read back you'll see that I agreed that the bow tie Christie shutter was a problem and does flicker. However I tend to live in the present(at least on my customers behalves) and not in the past which as far as the Christie you seem to be best at. Christie uses and has now for over 10 years a double speed single blade shutter and not a bow tie version. If you have customers with GP machines and haven't been converted to single blade shutters do them a favor and do so, its an inexpensive conversion and image quality goes from a 5 to a 9.5. The flicker problem of the bow tie shhutter is why they went to the single blade version and it got rid of all the annoying flicker problem. At least for myself I have but one P35C single blade shutter machine left running and gobs of 35GP's that have all been converted to single blade if they didn't have them.

Also, Your claim of the shutter cutting the aperture squarely stands with no proof of relationship to light efficiency, in fact I'll say it has way more to do with velocity then the angle of attack. If you look at the DP-70 shutter blade which is also VERY close to the film plane it is clearly the highest velocity blade of the bunch you'll find that it cuts the aperture somewhat diagonally but it still is the most efficient mechanically based shutter with a published spec of 54%.

Another interesting projector with an annoying flicker problem was the Motiograph AA. Either its double or single shutter versions both had a similar flicker problem. Motiograph even admitted this but was never able to do a "fix" for it because they thought the problem lie in "lost Motion" in the 21 pair gear train. Interestngly both the AA versions used drum shutters that ran at the same velocity. The double shutter was abandoned both because it didn't do anything to get rid of the flicker and it was difficult as hell to replace the double shutter bearings.

Mark

Posted by Steve Guttag (Member # 268) on 10-27-2007, 09:58 AM:

Mark, all the single blade shutter did was reduce the flicker (and double the velocity which improved efficientcy)...it did not eliminate the flicker. I don't live in the past but certainly work with much that is in the past. I tend to put in most of the latest and greatest too. I'm dying to meaure the new Kinoton Premier shutters...they look to be substantially more efficient than 50%! Their improvements come from a faster intermittent allowing a shorter closed time. The blades are just over 80-degrees.

Posted by Mark Gulbrandsen (Member # 72) on 10-27-2007, 11:31 AM:

quote: Steve Guttag
I'm dying to meaure the new Kinoton Premier shutters...they look to be substantially more efficient than 50%! Their improvements come from a faster intermittent allowing a shorter closed time. The blades are just over 80-degrees.

Oh come on... thats not anyting new... Premiere my ass. Nothing more than a high speed pull down, perhaps based on the Kodak starwheel patent combined with a narrower shutter. High speed stuff has been around since the 50's. Although you already know you will more than likely along with alot more light on screen see much improved image definition.

Donno why you see flicker on P35's... I certainly don't and we have many P-35's on small and huge screens running in excess of 16fl. Even the customers agree on ones that I converted... that the flicker is gone.

Mark

Posted by Monte L Fullmer (Member # 2797) on 10-27-2007, 01:33 PM:

quote: Steve Guttag
Likewise with the various digitals...I still find it unsettling that I like the sound of SDDS the best overall.

AND,what's interesting, is that I fully agree with you on this one.

When I used to work in a megaplex, we had 3 houses with SDDS, and I would always use this format over DTS and SR-D which were also included in the soundrack.

Granted, the compression rate with SDDS was higher than DTS, yet lower that SR-D, but somehow SDDS just had the dynamics and sound quality better than the other two, which I don't know what it was.

Yes Steve, I also agree with you on how one can tell which machine is used when visiting other cinemas due to that "telling" since each has their own personality.

I want to add a small comment in here that I've been noticing at my theatre since this topic of flicker is on our minds: I've got the PR-1050's, ran Century SA's, plus ran P35s with the single wing shutter and what's a bit interesting is that with all three, this flicker issue is basically there since we are watching the picture on the screen in the save viewing angle as the projected image (kind of looking behind the projected image), yet when we go downstairs, obviously, we're at a different viewing angle and don't notice that flicker as much.

Also, maybe some people are more keen in seeing those 48Hz pulses of light than others, where in theroy, our brains absorb that frequency of light pulses into one - like with me with CRT computer monitors: The default 60Hz refresh rate drives me insane due to the flicker where I make sure that I've changed the setting to the higher 75Hz refresh rate.

-Monte

[ 10-27-2007, 03:27 PM: Message edited by: Monte L Fullmer ]

Posted by Louis Bornwasser (Member # 3063) on 10-27-2007, 03:18 PM:

deleted by Louis--off topic

Posted by Mark Gulbrandsen (Member # 72) on 10-27-2007, 06:52 PM:

Monte,

I think what you're trying to say is that different people perceive the flicker differently and that is very true indeed. I still haven't noticed any flicker to write home about out of either P-35GP with the single shutter, a Simplex X-L, or the DP-70... @ 16fl relative I perceive them to all be about the same.

quote: Monte L Fullmer
The default 60Hz refresh rate drives me insane due to the flicker where I make sure that I've changed the setting to the higher 75Hz refresh rate.

Its funny that you bring this up because the 60 hz refresh rate actually drove a neighbor friend of mine to have attacks and she would convulse and then pass out. It was only when one morning that I was talking to her over the phone and she mentioned she was doing some work on the computer and she stopped cold in the middle of the cnversation... and I heard the phone hit the floor. I hung up and called the ambulance right away and they got there just in time. Changing the refresh rate on her monitor to 75hz stopped the convulsions.

Mark

Posted by Monte L Fullmer (Member # 2797) on 10-27-2007, 07:08 PM:

Thx Mark..now I can see where this is all coming from since the key in this whole side topic discussion is the 16fl light output, not so much of shutter structure and operation - where I came up with that end credit flickering if the bulb is too close - you back off the bulb, light output decreases and the flicker becomes less noticable..

Thus, the magic forumla in this whole disussion is to get as much light on the screen and less noticable flicker to go along with it..

(guess why IPC designed the Hi-Speed Intermittent assembly for the Simplex XL to allow some of that formula to be solved.)

Maybe why this is another reason for the immense desire for digital projection ... nice 20plus Fl, and no flicker.

-Monte

Posted by Mark Gulbrandsen (Member # 72) on 10-27-2007, 07:29 PM:

No, Digital projection spec is actually 14fl. If you go over the prescribed 14fl you wash out the blacks and lower the overall image contrast dramatically. The average human eye is very suceptable to seeing the 48hz flicker from a film projector when the light level is between about 18 to 20 fl.

Mark

Posted by Steve Guttag (Member # 268) on 10-27-2007, 08:24 PM:

The Kinoton premier machines are electronic intermittent...so not likely to be based on anybody's starwheel.

Like you said though...I'm looking forward to measuring the improved light AND the improved image resolution. I just took deliverly of 6 machines...4 are 35/16s and 2 are 35/70s. Two of the 35/16s will also be virtual 3-wing machines up to 25fps so those should look really fantastic.

Perhaps I am more senstive to the flicker than others...just like single chip DLP...they are downright annoying to watch. As for film projectors...I just don't like the Christie look...sorry...it has improved immensely over time in both picture and sound but still leaves a lot to be desired in my book.

Steve