This is topic Xenon lamp alignment in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.


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Posted by Matthew Taylor (Member # 2310) on 04-02-2005, 07:23 AM:
 
I'm hoping you can help me. I have got my small Cinemaccannica CX-450 working reasonably well with my Prevost P70. I'm certain I could squeeze some more light out of it with better alignment though.

The facts are this; I don't have an 'alignotron'. I don't know the optimum distance between the lamp and the gate.

To the best I can without the correct tools, how can I;

a) align the lamphouse in relation to the projector both vertically and horizontally (the lamphouse is sitting on bits of wood at the moment)

b) best focus/align the mirror once the lamphouse is in the correct position.

I have looked at the archives and seen the 'string method' mentioned but found no reference to what it actually is.
 

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Posted by Darryl Spicer (Member # 711) on 04-02-2005, 12:37 PM:
 
I guess you could try to project the light to the screen with out the lens and make sure that the dark spot is as centered to the screen as possable then try and focus the light with the scope lens in placefor the brightest picture with just a bit of darkness in each corner of the screen. Making sure the light is evenly spread.
 

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Posted by Gordon McLeod (Member # 33) on 04-02-2005, 12:44 PM:
 
Cut out two disks that are the diameter of the ens mount
and puch a pin hole in the dead centre (for this to work they have to be accurate)
remove the lamp and in the cntre of the mirror is round tube
look through the two pinhole to align the lamphouse so that the centre of tat tube is in line ith the pin holes then install the lamp and make sure it is visible on the same axis that will get you in the ballpark

The original method for these was with steel rod and dummy lens
 

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Posted by Jacek Dejnarowicz (Member # 3062) on 04-03-2005, 05:01 AM:
 
The optimum distance between the lamp and the gate depends on your mirror and lens. The lamp need to be at the first and the gate at the second focus of the mirror. And finally the size of focused light beam must be equal aperture of the lens.
I don't know if it's clear cause of my weak english. I think the best way is to find specification of your lamphouse.
 

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Posted by Darren Briggs (Member # 1071) on 04-03-2005, 08:03 AM:
 
You can also focus the lamp on a wall by pointing the lamphouse at a wall, to ensure you have the mirror and xenon perfectly aligned. then mount the lamphouse on the projector ensuring that the image of the xenon is bang in the middle of the screen, or using the method using string works well.
 

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Posted by Greg Mueller (Member # 17) on 04-03-2005, 10:49 AM:
 
Matt
If you send me a picture of your set up, maybe I can help you figure it out.
 

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Posted by Matthew Taylor (Member # 2310) on 04-03-2005, 05:08 PM:
 
Thanks Greg, I will do. It may take a couple of days because I have to borrow my brother's digicam.
 

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Posted by Gilbert Travin (Member # 2138) on 04-04-2005, 07:03 AM:
 
Matthew ;

You can use a laser pointer ... to align film gate and lamphouse.
then you can align projector axis with screen axis. But the "great" problem with Prevost is to adjust correctly the turret because there are too many adjustments of the turret (I believe 3 adj. : lock position, 35/70 translation and each lens ...) : this operation will be long.

If your mirror is designed for 16 mm operation, you will have "dark" zones on the two sides of the screen, especially in 70 mm .

Good luck !
 

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Posted by Gordon McLeod (Member # 33) on 04-04-2005, 09:25 AM:
 
The CX450 and CX900 are basically a 16mm design and a beam diffuser is required in the snood to expand it to 35mm
 

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Posted by System Notices (Member # 2357) on 09-13-2006, 06:42 AM:
 

It has been 526 days since the last post.

 

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Posted by Marin Zorica (Member # 1716) on 09-13-2006, 06:42 AM:
 
Good subject in topic, so I won't start another topic, I just gonna ask something.
Can anybody tell me a distance from center of lamp to gate???

I using 900W vertical lamp with 350mm diameter mirror, bur mirror isn't problem because i have original holders for lamp and mirror conected together, I just must set that holder to lamphouse!
 

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Posted by Monte L Fullmer (Member # 2797) on 09-13-2006, 10:27 PM:
 

quote: Marin Zorica

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Can anybody tell me a distance from center of lamp to gate???

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quote:

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You would have to check what are the requirements for the lamp house used with your machines..

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quote: Gordon McLeod

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you would have to find out who did or make the conversion and ask them

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hmmm...I thing flying to moon is simpler to do than that

I figured out stuff, distance from gate to center of lamp is 71cm, and from lamp to mirror is 10cm!
 

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Posted by Eric Robinson (Member # 2966) on 09-15-2006, 01:43 AM:
 
For a parabolic mirror, all rays of light emitting from the focus reflect off the parabola and travel parallel to each other.

Since this is true, if one were to shine a laser pointer into the mirror at a perfect angle such that the vertical angle would not vary up or down and the horizontal angle would not be off to the left or right, one could shine the laser pointer into the reflector at any part of any surface and the light from the laser would bounce to the focus point of the parabola.

If one were to mount a thin protrusion centered in the parabolic reflectors rear hole whereby the protrusion would extend into the reflector a sufficient distance, one might see the light from the laser at the focal point. One could then reasonably estimate where the arc of the bulb should be with respect to the reflector.

This is just a theory of mine. Does anyone agree or disagree with this idea?

Or maybe flying to the moon might be easier
 

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Posted by Greg Mueller (Member # 17) on 09-15-2006, 12:27 PM:
 
Here's how I recommend it be done
http://www.muellersatomics.com/alignotron.htm
 

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Posted by Charles Greenlee (Member # 3856) on 09-16-2006, 12:18 AM:
 
Wonderful tool, not that I should ever have to use one as a lowly projectionist., but if/when I get up to sound tech. something like that may come in quite handy.
 

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Posted by Frank Angel (Member # 248) on 09-19-2006, 10:20 AM:
 
It sure would be nice if the pedestals themselves would have alignment adjustments so they can correctly (and EASILY) align the lamphouse dead-center with respect to the trap. You can futz around with mirror all you want, but if the lamphouse isn't sitting true center, then all you will be doing is trying to correct for that initial misalignment.

Seems to me something as so primally important as the lamphouse position as it sits on the pedestal should have adjusting rods so that they can be as easily manuvered as the adjustments on the mirror.

I guess this is less of an issue when dealing with an integrated console, eh?
 

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Posted by Steve Guttag (Member # 268) on 09-19-2006, 11:22 AM:
 
Frank, Good pedestals DO have proper lamphouse adjustments. In fact, I'll get a lamphouse on a pedestal aligned far better than a console to projector any day. Most consoles suck in this manner.

Examples of pedestals that have lamp table adjustments include Century and Ballantyne (still available...called the 2500B). Simplex only offered limited adjustment on theirs and I don't like using them as a result.

Steve
 

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Posted by John Pytlak (Member # 331) on 09-19-2006, 07:59 PM:
 

quote: Eric Robinson

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For a parabolic mirror, all rays of light emitting from the focus reflect off the parabola and travel parallel to each other.

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quote: Steve Guttag

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Simplex only offered limited adjustment on theirs and I don't like using them as a result.

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