Film-Tech Forum ARCHIVE: 2000ZX light output

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Posted by David Stone (Member # 4846) on 03-10-2011, 04:23 AM:

Hi Guys,

Can you increase the cuurent on individual channels without a technician with a laptop connected to the 2000ZX. Is there anyway of getting into the system.

Also do you suggest to have Lamp LOC on auto increase so each time you select it, it maintains the same light output as the bulb ages.The technicians in OZ seem to turn this function off.

Finally should the light output drop off as the projector ages. The techs here say this is normal and will drop off at least 10% each year as it degrades

Cheers,

David.

Posted by Brad Miller (Member # 2) on 03-10-2011, 01:41 PM:

The ZX has a web GUI, but if you are not a certified technician giving you access to it could cause a lot of EXPENSIVE problems and failed shows. You need to get with your tech for the answer to that questions.

Yes the ZX can automatically increase power to the bulb to continue to meet light levels, but this is a horrible idea. It will kill the life of your lamp by constantly pushing it harder and the Lite Lock function can actually overdrive your lamp without you realizing it and cause it to explode. Your techs are smart to disable it.

Light dropoff as the lamp ages is a fact of life. However it is much more significant than 10%. This is why when equipment is being spec'd for an installation, ridiculous numbers such as "this projector is good for screens up to 105 feet" are nothing more than marketing bs. Sure with a super duper 7000 watt lamp with 0 hours on it burning at 120% power and a really high gain screen without any port glass can do it, but it is NOT realistic and will only serve to produce terrible presentations. Calculations should be made before the equipment is even purchased what the light will be at more than 50% use on the bulb to ensure spec can still easily be achieved.

And this is not Christie-specific. The info above applies to all projectors.

Posted by Dave Macaulay (Member # 813) on 03-10-2011, 06:34 PM:

Christie's lamp-loc and Barco's CLO are great if you have the right lamp. Brad's point about lamp selection is important, if your lamp is running at 90% or more when new to hit the target screen illumination then it's going to max out pretty soon. I think 75% power or so to make the 2D spec with a new lamp is ideal, running lower power will cause trouble and this should get your target illumination for most of the lamp life. Barco will not overdrive the lamp much with CLO enabled, I think Christie is the same with a max current level for whatever lamp is installed.
Using these automatic systems should ensure you have the screen lit as close to the specs for 2D and 3D as you can get (realistically you're going to be too bright at minimum power on 2D where you have a lamp with headroom on 3D). As digital rolls out we'll be seeing more 2D only systems where the lamp sizing will be much simpler.
If you just set manual power levels for each format your light will unavoidably drop as the lamp ages. Cinemas with light meters and the expertise to use them are rare.

Posted by David Stone (Member # 4846) on 03-10-2011, 08:23 PM:

Hi Brad & Dave,

Thank you for the advice.

The 10% fall off in light I refered to was not the xenon, but the light engine itself. The techs downunder say you should expect this to degrade @ 10% per year as well as the natural fall off the bulb ?

I use a CDXL30 bulb, REALD Z screen, 1500watts 2D W/S, 1700watts 2D C/S, 2500watts 3D W/S, and 3000watts 3D C/S.

65' throw, 32' scope picture.

Do these settings sound usual, or maybe there is an alignment problem.

I did use a CDXL30SD, but it would drop out regularly as 2D W/S would run only 1100 watts
Cheers,

David.

Posted by Brad Miller (Member # 2) on 03-10-2011, 11:21 PM:

Hi David,

You're killing your bulb turning the current up and down between flat and scope. It is bad enough you are turning it up and down between 2D and 3D, but going to such an extreme between flat and scope is asking for early failure.

Posted by Chase Pickett (Member # 5975) on 03-11-2011, 02:51 AM:

quote: Dave Macaulay
if your lamp is running at 90% or more when new to hit the target screen illumination then it's going to max out pretty soon. I think 75% power or so to make the 2D spec with a new lamp is ideal

My home office decided to use a smaller bulb (4200w) in a Sony on a screen 105' wide where we were using a 5000w bulb for 35mm. Needless to say we had to run it at 100% when the bulb was new. Then they wondered why the bulb exploded at 680 hours. (700 hours was the warranty limit) Now we have a christie in there with a 6000w bulb running at 75% when new [thumbsup]

Posted by Marco Giustini (Member # 4544) on 03-11-2011, 02:55 AM:

What is the right procedure then? If your 3D system has a light efficency of 10/15%, either you drop the lamp current, or you end up with 30+ FL in 2D!

Why don't manufacturers install a mechanical iris inside the projector for adjusting light? Then the lamp could be burn happily at its rated current, increasing its life.

Posted by Steve Guttag (Member # 268) on 03-11-2011, 07:11 AM:

You can also change lamps between 2D and 3D. If you have side masking...USE AN ANAMORPHIC...yes they cost money but you only have to buy them once. The increase in light is significant (about 23%).

-Steve

Posted by Tim Asten (Member # 4051) on 03-11-2011, 08:24 AM:

Nobody seems to have answered Davids question regarding light loss from an ageing D-projector. Is this true? 10% per year seems rather a lot. [Confused]

Posted by Marco Giustini (Member # 4544) on 03-11-2011, 05:13 PM:

Steve

Not arguing the anamorphic subject, but why not install an iris in every digital projector? Anamorphic or not, wouldn't it be a better way to control light?

And, as far as I know, using an Iris would increase contrast ratio as well!

Posted by Steve Guttag (Member # 268) on 03-11-2011, 05:31 PM:

The Iris you speak of would likely be back in the lamphouse area, not in the lens...in the lens would jack the price of each lens way up. With an IRIS you are driving the lamp okay at all times but you are always driving it high.

With an anamorphic, you lower the lamp demands for ALL formats...in that Scope's light requirements are much closer to Flat's. With an iris, you are lamping for your worst format (scope) and throwing that light, electricity, lamp costs, away. With an anamorphic, you just use a smaller lamp or use less electricity at all times.

And for 2D/3D...change the lamp. If you have a Barco, then you have lamphouses...the lamphouse has a board on it that stores the lamp info...as such, as one swaps between the 2D and 3D lamp, the hours and operating range...etc are kept up. Since it is pin registered it need not be aligned one a simple 2D/3D swap...only when a new physical lamp is replaced.

As for lumen output decay within the projector over time...I don't think anyone has really published what that is. One would also have to attribute the source of the decay. That is, is it the reflector of the lamphouse, section, the light pipe, folding mirrors, imagers, prism...etc. Then compare those loses to those of the port glass or the screen itself (and color correcting for its aging). It will be real hard to pinpoint that the projector is losing say 10% of its light just due to aging...there are too many factors...including the environment that the projector is running in.

-Steve

Posted by Paul Mayer (Member # 355) on 03-11-2011, 06:45 PM:

I thought anamorphics were not allowed under the new DCIP specs. Nothing that modifies the shape of the pixels, or something to that effect. Or am I thinking of something else?

Posted by Brad Miller (Member # 2) on 03-11-2011, 07:08 PM:

I am not a fan of the whole "change the lamp" theory. Anytime a lamp is touched, you are killing some of the life. This is why I have found over many years that even rotating the bulb shortens the lifespan of a bulb.

3D makes this whole issue of getting great bulb life a huge mess. [thumbsdown]

Posted by Steve Guttag (Member # 268) on 03-11-2011, 08:12 PM:

Anamorphics are NOT excluded from DCI spec. Source content has to be square pixels. And the "scaling" is not to have visible artifacts...which is subject to interpretation. What IS in the DCI spec is that an Anamorphic (or other aux lens) is used, it has to be accomplished automatically without human intervention.

As for changing the lamp...this is a case where Barco's lamphouse system prevails over the others...one does not "touch" the lamp on a lamp change...just pull the whole lamphouse and put in the other one.

I have mixed views on rotating lamps. If the projection angle is steep, rotating the lamp will do wonders for helping its life. I've also found that some of the high-brightness lamps with VERY large anodes benefit from rotation.

In general, however, I agree with not rotating lamps.

Without changing lamps, however, it is impossible to get a good light balance between 2D and 3D...there is just too big a difference in the light requirements.

One thing I forgot to mention previously regarding the iris theory...if the iris is not in the lens, then you don't benefit in contrast or focus...you just piss away the light.

-Steve

Posted by David Stone (Member # 4846) on 03-12-2011, 01:13 AM:

Hi Brad,

That you for your help. I will pass your comments onto the Techs and have them service the system again asap. They only did a complte annual service on Jan 31.

Cheers,

David.

Posted by Marco Giustini (Member # 4544) on 03-12-2011, 01:05 PM:

I am with Brad about the lamphouse. I do agree that it would be the best idea, but this is not the case in the real world, where the average projectionist is a curse for the equipment they are suppose to look after [Smile]

And looking at the issue with real world eyes, I doubt cinemas will all go for anamorphic just to save lamps or to give the best presentation both in 2D and 3D. A mechanical Iris (as you said in the lamphouse to save money, I agree) would be cheap to implement - I reckon.

Why not installing an Iris as default, and leave to the exhibitor the best (and more expensive) option of the anamorphic?

I agree that driving the lamp high all the time is a waste of money, but at least the presentation would be optimal all the time. At present cinemas are forced to show over-bright 2D picture.

Posted by Steve Guttag (Member # 268) on 03-12-2011, 04:33 PM:

Marco...by your own argument (cheap exhibitors won't buy the anamorphic)...also rules out the iris. And, from what I've seen, they, by and large, just don't have the right light levels...Scope is under lit if Flat is properly lit.

If you don't vary the light output and you don't do anything to equalize the light, you have can't have proper light for both formats.

Again, Barco's lamphouse solution would work for 2D/3D since the only person "aligning" anything is the person that replaces the lamps themselves. it isn't high skill to change the lamphouse.

-Steve

Posted by Kris Verhanneman (Member # 5562) on 03-13-2011, 05:17 AM:

And how would you proceed when they program you
14h30 2D screening 16h15 3D screening 18h15 2D screening ... 20h 3D screening ... ?

Asked the same question to our technicians when they installed our first 3D dolby screen.

Posted by Marco Giustini (Member # 4544) on 03-13-2011, 06:53 AM:

or in a fully automated booth like Brad's.

If the Iris is as expensive as an anamorphic, then you may be right! About the light output, the idea was to design the system bearing in mind the less efficient format (Scope, 3D) and then adjust the iris for other formats.
You could also adjust the rectifier power to save energy, and have the Iris to help when that is not enough.

Posted by Steve Guttag (Member # 268) on 03-13-2011, 06:56 AM:

You could do it with the Barco lamphouse.

But what we really need is the lamp-turret with up to 4 lamps (FLAT/SCOPE 2D/3D)...or just 2 Lamps and an anamorphic (my preferred way). If you have constant width screens...then just the 2-lamp turret would be sufficient.

-Steve

Posted by Marco Giustini (Member # 4544) on 03-13-2011, 07:51 AM:

Lamp turret?? You mean multiple lamps in a lamphouse?

I'm afraid I have to disagree this time.

Posted by Kris Verhanneman (Member # 5562) on 03-15-2011, 09:33 AM:

I think the real solution is way different ... available one day I hope.
Replace the Xenon lamp by a laser light source.
That way you can adjust more your light output to the needs of your screening.

Posted by Marco Giustini (Member # 4544) on 03-15-2011, 06:32 PM:

Can lasers be adjusted in brightness?

Posted by Carsten Kurz (Member # 5396) on 03-15-2011, 06:39 PM:

Yes, they can. What's more interesting about lasers and 3D: Lasers have a very small etendue - they do not need mirrors and the like. In consequence, you can easily 'stack' laser modules for increased brightness.
You might have two or more laser modules in a future 3D machine, both (all) being used for 3D, or only one of them for 2D (switched on alternately between shows to balance wear).

There are some dual- or even quadlamp business/E-Cinema projectors with UHP lamps, but that system is quite expensive and complicated to build (even with these smaller lamps) and the light output is still compromised. Usually the largest benefit is automatic lamp switchover in case of failure.

- Carsten

Posted by Marco Giustini (Member # 4544) on 04-11-2011, 01:14 PM:

Back to the 'keep the right light in 2D' topic, how do cinemas using 10-18% light efficient 3D systems can achieve 14FL on 2D these days? If you have 60FL in 2D at 100%, how do you lower the light on screen to reach 14FL, in the real world?

Posted by Steve Guttag (Member # 268) on 04-11-2011, 02:14 PM:

If you have Barco...change lamphouses...quick.

Others typically have the light vary (hard on the lamps) and you can't get it to come in properly on both.

-Steve

Posted by Carsten Kurz (Member # 5396) on 04-11-2011, 02:57 PM:

Well, first of all, it's not so bad to have more than 14fL in general. There's no flicker as with 35mm, so there's no penalty with more light (except energy cost).

One should probably swap lamps between 2D and 3D. However, swapping bulbs so often is another risk. Best is to use a 3D system with a better light effciency.
Or, if you have enough screens, dedicate one or a few to 3D only and always run it on max brightness. Dual projector 3D is another (expensive) option. Currently, I don't see the ideal solution to that problem.

- Carsten

Posted by Marco Giustini (Member # 4544) on 04-11-2011, 03:17 PM:

Steve

I am wondering what happens in the real world. Barco will not allow to power your lamp less than 50-ish% if I am not mistaken. If you have 60FL at 100%, you can achieve 30ish at 50%.
As Carsten pointed out, it's not so bad. But I was wondering: any ways to achieve the DCI standard 14FL on a 3D projector (without replacing anything) these days? Sure, you can do it if you have a RealD-XL, but what about the other systems?