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This topic comprises 2 pages: 1 2
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Author
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Topic: Barco light sensor
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Jay Glaus
Expert Film Handler
Posts: 123
From: Pittsburgh, PA USA
Registered: Dec 2010
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posted 04-26-2015 06:07 PM
I was touching up the alignment on my 32B today, and noticed something strange. I was watching the alignment chart on communicator, and as the bulb is on, it will be reading 10.50 Ft/L, and without really touching anything will plummet to 8.00 within a second. Then, eventually, it will come back up. I know sometimes the arc can wander and you can have a slight flicker, but I would have to believe a sudden drop of slightly over 2 Ft/L would be noticeable to the eye.
The other thing I thought was strange, was a few times it plummeted, no matter what adjustment you made, it really didn't change it until it decided to come back up. I honestly do not believe the brightness is changing as much as it is the number on the sensor. The bulb is fairly new, and i cannot really see any flicker.
I ended up aligning the bulb off my eye, because the number on communicator began to bounce so rapidly, it basically became useless. I tried closing and reopening communicator too, and rebooted the machine once. I'm sure the alignment isn't great, but it will get me through the night.
I don't have a light meter, but I know somebody who does. He's going to bring it out in a day, and we are going to try to align the bulb using an external light meter. I even tried making a new calibration file for the light sensor, on the assumption that i was getting 10 ft/l on the screen. Even though the calibration file would be incorrect, I wanted to see if it would still bounce with a new file, and it did.
I believe the light sensor in that 32 is going. Does anyone else agree?
Thanks, Jay
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Steve Guttag
We forgot the crackers Gromit!!!
![](http://www.film-tech.com/ubbmembers/268e.gif)
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 05-02-2015 01:57 AM
That is not entirely correct. Christie uses a "target number". It is just not referenced to any particular fL reading. When I install a Christie projector, I set up any desired light loc calibrations I may need and name them appropriately. That is, if I want a 14fL Flat and a 14fL scope...I'll manually set the light to 14fL and then label the setting something like FLAT14fL and set the lightloc to that number. Likewise for the Scope format (and on down the line for any/all lens zoom or anamorphic settings). So while the Christie will not read out in fL (you can "calibrate" its sensor for ONE format, that is indeed inaccurate) you can set up as many suitable lightloc calibrations that are as accurate as your light meter. The projector will keep the lamp at that level to the best of its ability (and potentially to the lamp's detriment if allowed to go over 100%)
For sure though, Barco has everyone beat on the lamp calibration thing and they let you have it read out in fL with reasonable accuracy (not taking into account the optical items after the sensor...i.e. screen, port glass).
THE most worthless sensor is NEC's. It too is just a number but it has no basis on anything, including brightness. Setting for the highest number often doesn't mean the brightest or most even picture. That said, NEC will, like Christie allow you to "mark" your desired setting, save it, recall it and use "Feedback" to account for lamp aging. From what I can tell in my limited tests, it seems to lock onto your settings pretty well.
What Christie really beats the others on is lamp alignment. What a pleasure that thing is...it gets you 95-100% there and it does it pretty darn fast on the series 2 projectors. Barco's automatic lamp adjustments (if you buy the rather expensive upgrade) is horrendously slow (15 minutes or so) and is hit/miss at best on the alignment and seemingly never gets it 100%. That said, Barco is the clear winner on manual alignment...the lamp adjustments combined with the "green dots" makes it rather quick and accurate. NEC is the clear loser there with the most sloppy lamp adjustment that seemed to copy Christie's old "H" series lamp adjustments...with all of their failings.
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