Film-Tech Forum ARCHIVE: Rotating Xenons? Pro or Con?

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Posted by Michael Rourke (Member # 1142) on 04-11-2002, 11:25 PM:

I was taught to rotate at half life, and then some time later I was told that it really doesn't matter. Then again some time later I was "strongly advised" NOT to rotate bulbs. Then I read on this site from various operators that they have bulbs going 6,000 hours with 5 rotations mixed in. Who is right? I notice also that bulbs don't have the nipple on the envelope anymore, is this to discourage rotating?

I ask because I have been having tons of problems with my bulbs since I stopped rotating, plus we switched from Osram to ORC (not happy), and I have had problems with bulbs fusing to the negative end clamp on my Christie SLC's.

I am trying to gather enough evidence against ORC to get my superior to make another switch either back to Osram or to Christie xenons. I have already printed out the ORC Xenon bulb review on the site, and some testimonials would help too. Thanks.

Posted by Ian Price (Member # 14) on 04-11-2002, 11:31 PM:

I never rotate my lamps. Please refer to the previous thread titled Lamp Rotation

Posted by Paul G. Thompson (Member # 655) on 04-11-2002, 11:49 PM:

Michael, if the bulbs are fuseing on the negative end, I would highly recommend that the collar be tightened in accordance with the manufacturer's recommendation upon installation of the bulb.

It might be a good idea to inspect that area perodically to make sure they are tight.

If the bulbs are turning black, I would rotate them at half-warrenty life.

Posted by Michael Rourke (Member # 1142) on 04-12-2002, 12:04 AM:

I replaced all the negative end clamps (even those that weren't fused to a bulb) and all the cathode leads as well.

I was told not to overtighten the socket head allen on the clamp or the bulb would fuse, but then when I took my reoccuring problem to Christie they told me to really wrench down on that screw.

Thanks Ian for informing me of the related post, I promise to use the search feature in the future.

Posted by Paul G. Thompson (Member # 655) on 04-12-2002, 01:34 AM:

Yes....heavy current flow through a loose or snug mechanical connection will cause plenty of heat. It'll get hot enough to weld itself to the other part.

Anytime a bulb is changed, the critical parts should be examined for evidence of pitting or overheating. If this condition exists, you can tighten things down until you are blue in the face, only to find later that the situation has gotten worse.

The parts that show overheating and pitting should be replaced. If the parts are not available, at least clean them up if at all possible. Lousy mechanical connections will probably void the warrenty.

Posted by Don Sneed (Member # 955) on 04-12-2002, 04:27 AM:

I have been told not to rotate a bulb, some manules say it is not needed.....I say "YES IT DOES" .... I tell everyone we install for to rotate the bulb 1/4 turn every 500 hours to burn the anode & cath. evenly, if you don't the bulb will flicker due to the anode & cath. burns unevenly which will cause the flicker, at 500 hours, turn 1/4 to prevent this....even bulbs that starts to flicker, by turning 1/4 or even a little bit more in most cases after a couple of days the flicker will be down to a minim or gone, if that don't work, turn a wee bit more, agin after a few days it should be back to normal, not in all cases but the majority will work it out & start to burn evenly..now of course this is only for the Horizontal lamps not the vertical, there is nothing that can be done about those accept to change them....by doing this rotating, you can get 3,000 to 6,000 hours easly from the bulb.....

Posted by John Pytlak (Member # 331) on 04-12-2002, 07:23 AM:

Rotating a horizontal xenon lamp usually does help to even out the electrode wear and the blackening of the envelope as the lamp ages.

Electrical contacts need to be tight. Any resistance at the contact will cause a voltage drop and heating, and may "weld" the contact.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

Posted by Mark Gulbrandsen (Member # 72) on 04-12-2002, 09:14 AM:

With me it depends on if there is someone at a given location that is capable of rotating a lamp correctly or not. I service a number of locations that do not have anyone with sufficient ability to do this correctly. At these locations they leave them alone and do not rotate them. At other locations that I do have rotate lamps they don't seem to get any more or less hours out of them than the locations that do not rotate them. We sell only Ushio(Christie) lamps and the high quality of these lamps may have alot to do with that. Typically we see at least 4000 hours from a 2kw lamp, although I don't reccommend it. I have a number of customers that are adamant about changing them at the end or rated life which is 2500 hrs. One thing I do reccommend is to rotate larger lamps starting at 3kw every 500 hrs. Typically, one can get 2K hours from a 2.5K or 3K lamp this way.
Mark @ GTS

Posted by Pat Moore (Member # 380) on 04-12-2002, 09:45 AM:

I tend to come down more on Mark's side of this. Experience has taught me that there is no hard & fast single answer to the question.

The theory of rotation and why to do it is fine and logical. But I hear a lot of reports about unstable arcs and increased arc waver after rotation, especially when that's done at half-life. Supposedly you can run the lamp at a higher current, near its maximum for a few hours, and the arc will generally settle down. I've seen instances where that does work and others where it doesn't.

I like the quarter-turn at quarter-life idea a little better. I like rotating the lamp if there is obvious darkening of the quartz on the top-half of the envelope a little better than that.

The best for me is if: a) the lamp arc is not wavering, and b) the quartz is clear, then don't fix what isn't broken. The lamp is "happy", let it run.

I think Mark's statement about the capability of the booth staff to do this and monitoring the results is probably the most important factor.

Pat

Posted by John Pytlak (Member # 331) on 04-12-2002, 12:51 PM:

Pat:

I agree with your concerns. But if electrode wear/sag has progressed to the point where simply rotating the lamp compromises performance, it's obvious that the wear is uneven. Perhaps the solution would be rotating on a more frequent schedule?

Hard to argue with the point that many theatres today do not have anyone on staff that have the knowledge and skill to properly and safely rotate a lamp, and then readjust the alignment for optimum light output.

BTW, are lamp mount shims available to allow a 90-degree rotation? Are they normally supplied by the lamphouse manufacturer, or the lamp manufacturer?

Posted by Darren Briggs (Member # 1071) on 04-12-2002, 01:00 PM:

Well I run 2k lamps and rotate them every 500 hours, I was taught this and the theory behind it sounds good to me. If a lamp gets to 2500 hours and starts to flicker, doing the rotation normaly cures this.
After 3000 hours, the next time they flicker I replace them, as I would rather not have too lose a show due to a xenon going out and refusing to re-strike. So in a single projector screen running on average 4 shows a day, I get 6 months from a 2k OSRAM.

Darren

Posted by Bernard Tonks (Member # 809) on 04-12-2002, 01:16 PM:

I’m a great believer in rotating bulbs after 1000 hours, average life on a 2Kw was 2500 hours.

Yes Osram always supply a washer to enable a 90 degree rotation.

Posted by Scott Norwood (Member # 30) on 04-12-2002, 02:53 PM:

As another data point, I recently replaced a 2k Osram XBO which had just begun to flicker at about 3800 hours. It had not been rotated at all. This was in a recent-vintage Strong Highlight-II console with excellent ventilation. There was some uneven blackening, but the image on screen had looked fine up until that day.

On the other hand, at another theatre, it is rare to get more than 2000 hours out of the same Osram 2k bulbs in older Christie lamphouses (the ones they made in the late '70s/early '80) with somewhat questionable ventilation.

Posted by Michael Rourke (Member # 1142) on 04-12-2002, 05:51 PM:

To the guys that rotate every 500 hours: How many screens do you run?

I don't know if I could keep up with all that bulb maintennance with 11 screens, especially since 4 of those screens weren't being run by projectionists for 7 years and need a lot of work.

I was taught to have the "tit", "nipple" whatever at 3:00 or 9:00, and then rotate at half life. I was told NEVER to have the "tit" at 12:00, and I was never told about increasing the wattage after rotation. Like Brad, I am just running as close to 100% of the bulb wattage from start up to finish, but I think the ORC bulb aren't fans of this method and have yet to wow me with prolonged performance.

Posted by John Walsh (Member # 168) on 04-12-2002, 05:56 PM:

At the risk of repeating myself (and others) good ventilation makes bulbs last longer. We're doing about 800cfm on even 2K lamps, and getting great life; easily paying back the price of bigger ducts and fans required. For a problem lamp, experiment by asking your HVAC guy to install the largest fan allowed, and track bulb life.

Posted by Paul G. Thompson (Member # 655) on 04-13-2002, 04:00 AM:

John, there is no question about it. At the Stanwood Cinemas, we are burning 3,000, 4,000 and 4500 watt xenons in the Christie Consoles.

Don't ask me why so many different wattages for a 5-screen theater.

As I was rummaging through some old bulbs, there was a clear 4500 watt and a clear 3000 watt lamp sitting in the pile. I noted one 4500 watt lamp was pulled after 6,600 hours. The 3,000 was pulled after 3500 hours.

The remaining bulbs had well over 4,000 hours on them. Only two looked real bad, probably because they were operated out of parameters. When looked the booth over before we took over, I noted that one of the 3000 watt lamps was being operated at 125 amps.

One of those bulbs was from that lamp.

Now, the lamp exhaust......they are belt-driven with a 1/2 (maybe 1/3) horse motors. When they are all running, it sounds like a Diesel Locomotive rumbling through the booth. That's how big they are. The proof is in the pudding.

Oh, by the wey - they are Christie bulbs.

The draft at the console stacks is almost strong enough to suck your hand in. The duct work from the lamphouse to the fans are 12 inches in diameter. Very impressive cooling for the consoles.

Actually, I like the Christie Consoles, but as for the projectors, well.....that's a different story.

Posted by Mark Gulbrandsen (Member # 72) on 04-13-2002, 07:29 AM:

I suspect that some here are not aware of an important improvement in Xenon bulbs that was madeabout 5 years ago. This was the addition of a getter to attract the vaporized tungsten rather than let it deposit on the inside of the quartz envelope. This is the reason that lamps do not darken as much or nearly as fast as they used to. Like Paul, I ahve seen many a lamp go twice its rated life with no darkening at all. Thanks to the getter this can happen, before that many of us were pulling out lamps that were pitch black.
I visited a theatre not long ago in that had not changed, or touched its lamp in about 7 years. Yea, it was pitch black, and it had a 1/8" deposit of coal dust on it from the old coal heating system that was still in use, but it was still plugging along. Fortunately there are not may operators that are this ignorant, but you run into them now and then.
Mark

Posted by Ken Lackner (Member # 1002) on 04-13-2002, 10:22 AM:

I don't understand what you mean by "getter." Which part of the bulb is it?

It is our company policy not to rotate. I do believe the theory behind this is that the arc has found a spot where it likes to burn. It is happy. Rotate the bulb, and you scew that up. Does that make sense? I think so.

Some people I know also said they were taught to put the nipple at 3:00 or 9:00. Why?

Posted by Richard Fowler (Member # 893) on 04-13-2002, 10:51 AM:

The "getter" is a trap in the bulb to "get" loose particles that burn off the electrodes instead of ending up on the quartz tube. The nipple being at 9:00 or 3:00 lessen the chance that particles get trapped in the small nipple area and overheat the quartz.
Richard Fowler
TVP-Theatre & Video Products Inc. www.tvpmiami.com

Posted by Paul G. Thompson (Member # 655) on 04-13-2002, 12:16 PM:

Some getters were basically a small charge of gun powder or something that will go "boom". There were others, too. Some were fired by RF energy. Some were fired by electical current. The idea was the ignition of the getter would burn up any oxidizing impurities inside a vacuum tube, such as oxygen.

But it does not sould like the same type of getter Richard speaks of.

Posted by Rick Long (Member # 213) on 04-13-2002, 01:24 PM:

I haven't heard the term "getter" since the vacuum-tube days.

With limited manpower and a large number of screens to service, we don't often get out to perform routine service (at least the way it should be done) as often as we should, especially in out-of-town situations.

A manageress/projectionist in one of these locations asked me if I would change 4 of her 6 xenon bulbs for her. She was quite capable of doing it, but hey, since I was there anyways... She informed me that these four machines had not been changed since she was at the theatre, and had no idea as to their age.

I replaced these bulbs. Although they were dark on the top (obviously never rotated), the screen light wasn't that bad, and had very little, if any flicker.

In one of the lamps i found a xenon bulb record sheet. It had been filled out by a former union projectionist I know. I checked the serial number against the bulb I removed. Sure enough, this bulb, an Osram XBO 2500 W/hs, had approximately 7500 hours on it. Same with the other three lamps.

I attribute this not only to adaquate ventillation and quality Osram bulbs, but Strong switching rectifiers as well.

Posted by Brad Miller (Member # 2) on 04-13-2002, 04:17 PM:

Personally I get great performance out of xenons by just putting them in and letting them go. When I was working at the Chinese, Joe had shown me 2000 watt lamps that had ran 7500-8000 hours that still looked fantastic on screen. Before I left I had taken some out that had 8500 hours on them and still looked excellent! Those bulbs were still outputting great light on screen and there was no darkening of the envelope at all nor flicker.

I think it boils down to cooling, the quality of the xenon itself and the power supply driving the lamp. Nothing beats a Christie lamp in a Christie console. When working with other brands of lamphouses, I have been able to greatly improve lamp life just by increasing the CFM of the exhaust. Switching to Christie lamps helps too, but boost the exhaust and you'll probably be very surprised.

On a related note, even though this thread is specifically asking about rotating xenons, do be sure and take a good hard look at your lenses. I work 2 nights a week at the Galaxy and our scope images are incredible. However, our flat presentations make me want to run and hide. This is because we are using those damned Magnacom zoom lenses for flat!!! These things suck up light, resolution and even produce dark corners that is NOT the bulb being focused down too much. I brought in a regular 35mm lens a couple of years back and did side by side comparisons in the turret and the difference was like comparing 16mm to 70mm. Maybe Regal will fix this once and for all. (Hint, hint) Anyway, check your lenses (clean them too, of course), as well as the reflector and port glass if you are getting poor light on screen.

Posted by Pat Moore (Member # 380) on 04-13-2002, 05:17 PM:

John -- by "shim", I assume you refer to a washer that would be used on "HTP" style lamps, right? I think washers are normally provided by the lamp manufacturers for 180-degree rotation. "H" and "HS" styles can usually be positioned at about any angle. The "HTP" Christie styles I'm not sure about -- I think you need a washer to rotate them.

Brad -- interesting comment on the Magnacoms as a light eater. They were usually fairly efficient in my experiences with them. The theory was, of course, to use them with longer focal length prime lenses that generally had better depth of field and light throughput compared to fixed focal length prime lenses of the day.

Are the screens they are in using vertical masking? What's the prime lens they attach to? The dark corners might indicate some vignetting, which might be the Magnacom attached to too short a prime lens without the proper adapter to "close couple" it.

Don't get me wrong -- the newer fixed primes are generally a much better option, especially the PLUS lenses. The instances where I'd use a Zoom Converter (new version of the Magnacom) with a Prime lens are fewer.

Pat

Posted by Richard Fowler (Member # 893) on 04-13-2002, 05:28 PM:

There are many new lenses available, such as the Schneider Variable Prime lenses and more steps of focal length available that make most situations with a Magnacom not neccessary...unless you are using a lens slider instead of a turret or the Bauer projector many UA houses had in the 1970's which had a rotary turret but had the same prime and the "turret" had a Magnacom and an Anamorphic....retired many of those with other brands of projection equipment, with a great improvement of light and image quality.
Big Sky buys Kinoton and Prevost projectors to hang on their console plus supply a platter to create a package.
I am a great believer in good ventilation and we supply, when required, booster fans on consoles we supply since we have seen some very poor HVAC in many cinema projects. On rebuilt equipment packages we generally improve the ventilation on the orginal equipment. Air flow on the bulb seals have to stay within a specified range for long bulb life. In the early 1970's I was hired by a lamphouse manufacturer ( to be nameless )to fix scores of units where the air flow through the unit was unbalanced to the point that the rear bulb seal was overheating due to air starvation.
Richard Fowler
TVP-Theatre & Video Products Inc. www.tvpmiami.com

Posted by Brad Miller (Member # 2) on 04-13-2002, 09:46 PM:

Pat, to give you an idea of what's going on, we need 37.5mm lenses in virtually EVERY house, with I think only a couple of exceptions, which I believe should be 42.5mm and 32.5mm (it's been awhile since I checked it). The Magnacoms we have are older 80's vintage and are just horrible for this scenario.

A few years ago I took up a 35mm lens of mine and placed it in the scope position on the turret of a couple of projectors and flipped back and forth. While my picture was a bit too big for the screen, even with the extra magnification my lens was substantially sharper and brighter...and this was not me being picky. To keep the picture from hitting the lens barrel, whoever set up the lenses had to use an appropriate focal length prime lens so that the Magnacoms were as compressed as much as they could possibly be. Otherwise the picture is literally a circle. Still though, the clearance is so tight that even illumination in the corners is impossible. I'm not sure if the lenses have close couplers on them or not, I know we have them on our scope lenses, but I'd have to check the flat.

While I do agree the newer versions of Magnacoms are much better, this is just not the right way to do it. We have one house in the complex that runs with a fixed lens and that flat image is fantastic, despite top masking being in all auditoriums. And of course, ALL of our scope images are great.

(Just imagine how great flat films through a zoom attachment look with a 4500 watt xenon onto an 80 foot screen! )

Posted by Paul G. Thompson (Member # 655) on 04-13-2002, 10:09 PM:

Brad, is there a possibility that part of the problem might be the f-stop of the lense being way out of porportion with the f-stop of the mirror?

The reason for me throwing this question out here is because at this theater in Anacortes where I am now, we didn't have any vignetting until a bulb blew. It wanged the mirror so bad, it was junk. I sent you a picture of that mirror last month some time.

I temporarly replaced the Super-Lumex with an ORC XH series lamphouse, and I had no vignetting. When I replaced the mirror in the Strong and placed the unit back into operation, still no vignetting, except I had to re-trim the scope aperature about .001 inches on the sides. With the old mirror, I tried just about everything in the books to eliminate the vignetting.

Correct me if I am wrong, but I have heard that the f-stop of the mirror and lense should be as close as possible.

As per example, a 500-watt Kneisley has such a fast mirror that it seems impossible to get rid of a hot-spot on the screen when it is sitting behind a 35mm projector. Would a faster lense correct some of this problem? I am under the impression the f-stop of the lense should match the f-stop of the mirror as close as possible.

I have a lot to learn here....... Thanks

We need a "Lense 101" seminar in the tip section of FT.

Posted by Richard Fowler (Member # 893) on 04-13-2002, 11:56 PM:

Brad,
both Schneider and ISCO have lenses in the focal lengths stated...time to make the Magacoms into a paperweight

Richard Fowler
TVP-Theatre & Video Products Inc. www.tvpmiami.com

Posted by Steve Guttag (Member # 268) on 04-14-2002, 12:35 AM:

Since Brad says the image will get a circle as the magnacom is pulled out, then there is not a close coupler on the magnacom, as it should be...I don't see any light eating issues with magnacoms used correctly, nor image problems. But if you are using a Magnacom, you will generally get better results if you have a curved screen.

I have also found that Magnacoms do not perform equally across their range and depending on the geometry of the your screen system, it is better to favor nearly pulled out, nearly pushed in or somewhere in the middle. I would not dismiss Magnacoms out of hand though. They are not necessarily the best choice in all situations either.

Give a Flat or nearly flat (1/20) screen a standard fixed focal length lens will normally be the better choice, if you can get the image out of your projection system.

In some instances, I've had to use the little known .52X magnifier by ISCO...it comes in a type "F" for flat field (also the shallow curves) and a type "C" for deeper curves. One thing that baby will do is push the focal point forward and also not eat any light (it is a large and expensive piece)...for pictures, check out the Indianapolis IMAX 3D in the gallery here...there is a picture of the Norelco projector with it (a white lens cap is on it).

The new Zoom Converter type "S" has a much larger exiting element than the older Magnacoms so even short lenses will not have a vignetting nor light problem.

Steve

------------------
"Old projectionists never die, they just changeover!"

Posted by Brad Miller (Member # 2) on 04-14-2002, 01:23 AM:

Steve, I've never seen a Magnacom that didn't eat at least some amount of light. I'll agree that later models are better, but are you implying that using a close coupler will bring the light output up to the same level when using a fixed lens? I don't buy that. My 35mm lens looked spectacular when I did my side by side comparison. (Yes I know a close-coupler will help in the corners, but I'm speaking specifically of the light in the center of the screen in reference to Magnacoms eating light.)

The story I got from one of the techs who did the installation as to why we have all of these Magnacoms was that the wrong fixed lens sizes were calculated and when it came time to open and the installers found out the fixed lenses did not fit the screen that there was a mad panic of grabbing at zoom add-on lenses and older, longer focal length lenses that were laying around to get the theater open. According to the manager, some of the screens could only run scope films for the first couple of months because of this.

Adding to the craziness, apparently upon opening they burned a print in one of the large auditoriums on a 6000 watt bulb and the entire picture was shaking from the blower on the lamphouse. The solution? A smaller blower and 4500 watt lamps from that day forth. I installed the exact same make/model console last month at a theater with a much smaller screen using a 6K xenon and had no problems whatsoever. For reference we are speaking of the Christie SLC-45.

Posted by Steve Guttag (Member # 268) on 04-14-2002, 09:02 AM:

Going with a close coupler could very well increase your light output on the magnacom. If the image is approximatly the size of your exiting aperture of the magnacom, then think of the exiting lens as an f-stop iris. Pushing the rear lens closer will reduce this and place the picture in the middle section of the lens elements, typically the better resolving part.

Close couplers are not expensive...give it a try.

Steve

------------------
"Old projectionists never die, they just changeover!"

Posted by Pat Moore (Member # 380) on 04-14-2002, 09:41 AM:

I'll side with Steve and stick with my previous thoughts. Again, I've not seen the Magnacom's be "light eaters", especially if they are properly coupled with lens focal lengths they are designed to work with. The new Zoom Converters are much better than the old Magnacoms. It's more like newer technologies are more light efficient. Generally (emphasize "generally"), I would prefer a fixed prime lens instead of a prime coupled to a Zoom or especially to a Magnacom, but there are a lot of instances where Zooms are an excellent tool and can actually be a better choice. Curved screens are a great example.

Yes, if I take a Zoom Converter, properly coupled to the correct prime lens and compare it to a fixed focal length lens of the same resulting focal length, the light levels will be very close. Not too many years ago the combination would have been brighter and more uniform on screen than the single prime, but improvements over the past decade and especially in the last couple of years with prime lenses has changed that. I think there is still a place for Zooms, though, in some applications and have had great results with them. Does that mean I'd put them in every theatre? Nope.

Brad, sounds like there are application and/or coupling problems in your example. The true Magnacom didn't like working with a prime lens below 70mm (I think), and it needed close couplers to do that. Otherwise you will see vignetting and probably light loss as well. The Magnacom is nominally a 65% magnifier, so coupled to a 70mm lens the resulting focal length is around 45mm. To get to 40mm or below, they are coupled to 60 or 65mm and that's probably where the problem lies. If it's a late 80's installation, who knows what might be in there.

Like most things, a Magnacom is just a tool that functions fairly well if it's properly used. Newer tools and technologies do tend to be better, if properly used.

Pat

Posted by John Pytlak (Member # 331) on 04-15-2002, 10:03 AM:

Pat Moore asked: "John -- by "shim", I assume you refer to a washer that would be used on "HTP" style lamps, right? I think washers are normally provided by the lamp manufacturers for 180-degree rotation."

Yes, I meant the lamps that have the screw-in base. Didn't know if they came with shims/washers to allow 90-degree rotation increments.

Posted by Pat Moore (Member # 380) on 04-15-2002, 04:35 PM:

John -- I haven't seen washers for 90-degree rotation from anyone, no. Osram was the obvious one I first remember, and it allowed 180-degree rotation. I'm not sure what other manufacturers like Ushio might provide, if anything. Most of the warranty policies I've seen require 180-degree rotation, so that might be all there is.

Most systems will allow orientation of the lamp as desired, as long as they are not the "HTP" style cathode.

Pat

Posted by Wes Hughes (Member # 981) on 04-15-2002, 04:51 PM:

I have done many experiments with different makes of lamps and I get the best performance out of lamps when I DO NOT rotate them (3K and under).

Posted by Will Kutler (Member # 770) on 04-16-2002, 09:12 PM:

To me, rotating a bulb makes common sense in that it can help keep the tungsten electrode on a horizontal plane. But one thing that I have noticed on this thread is manufacturers instructions. If I remember correctly, Christie does not recommend rotating bulbs in their lamphouses.

Posted by Frank Angel (Member # 248) on 04-18-2002, 03:23 PM:

Has anyone worked with the new Schneider Variable FL lens? I know they were designed specifically to correct minor variations where the available focal lengths won't match the aspect ratio exactly. The adjustment will fix that so you don;t have to crop. But here's my thought, does the lens have enough of an adjustment so that you could use it to function for 1.85 and 1.66? Would it have that much FL range? It would be a boon to art houses to be able to buy one lens and use it for both formats. But then, what's the difference between this and a zoom lens? And wouldn't the Variable lens have the same disadvantages of a zoom....slightly less light transmission and resolution than a fixed focus?

Frank

Oh,and as for rotating xenons....I once worked a drive-in and we had rotating carbons.

Posted by Richard Fowler (Member # 893) on 04-19-2002, 12:34 AM:

The Schneider VPL lenses work within a limited range which is great for trimming for keystone errors et cetera but not enough or practical(due to the lens lock function and allen wrench ) to go between formats. The image quality is equal to a prime, hence "Variable Prime"
name. There are some zoom + integrated prime lens available which we use for rentals which have 15 - 20 mm range but the image is passable.
Richard Fowler
TVP-Theatre & Video Products Inc. www.tvpmiami.com

Posted by Pete Naples (Member # 761) on 04-19-2002, 10:04 AM:

What Richard said! I've used some of those Schneider variables too. They are not designed to cover more than one format, but to allow you to tweak the image size to get the aspect ratio on screen perfect.

Posted by John Pytlak (Member # 331) on 04-22-2002, 08:07 AM:

Pete said: "...allow you to tweak the image size to get the aspect ratio on screen perfect."

Yeah! A person who "cares about composition" to "Do Film Right":
http://www.kodak.com/country/US/en/motion/newsletters/notes/spring2001/pytalk.shtml