Film-Tech Forum ARCHIVE: Dichroic Filter or Cold Reflector?

This is topic Dichroic Filter or Cold Reflector? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=004656

Posted by Greg Mueller (Member # 17) on 03-12-2003, 06:57 PM:

I'm setting up to run some 3D and the instructions I have say...."Be certain that your lamphouse has "cold" reflectors or dichroic filters installed"....
I have a Super Lume-X lamphouse. Do they have "Cold Reflectors"???
The reflector is new. There are no filters

Posted by Jack Ondracek (Member # 1466) on 03-12-2003, 07:02 PM:

It is if it came from Strong. If it's an Ultra Flat re-do, it isn't.

Posted by Paul G. Thompson (Member # 655) on 03-12-2003, 07:18 PM:

I concur with Jack.

Posted by Greg Mueller (Member # 17) on 03-12-2003, 07:53 PM:

How do you tell?
Pics of the lamphouse in question at
http://www.muellersatomics.com/alignotron.htm

Posted by Sam Hunter (Member # 1119) on 03-12-2003, 07:58 PM:

Cool reading Greg. I don't have an answer but I have a question. Where does one find an Align-O-Tron?

I performed a search and found my answer. I forgot that Greg invented the device.

[ 03-12-2003, 10:15 PM: Message edited by: Sam Hunter ]

Posted by Richard Fowler (Member # 893) on 03-12-2003, 08:00 PM:

As seen from your photos you have a "cold reflector" due to the gold color of the reflective surface....as long as you do not have gold flecking near the arc ball position of the reflector, it should work well.....a dichoric heat filter in the douser area, angled properly, would give you more insurance.
Richard Fowler
Kinoton America Inc.

Posted by Darryl Spicer (Member # 711) on 03-12-2003, 08:08 PM:

Yes you should be able to use that type of reflector with no problems. We used that type years ago for 3D. Now the dichroic filters may be the glass reflector type where the ulta violet light passes thru the reflector to prevent loss of light output. It could be a filter placed in front of the light that magnifies the light output I have seen these but was never sure what they were called.

Posted by Phil Hill (Member # 371) on 03-12-2003, 08:33 PM:

Greg: Yes, that is a "cold" reflector. Are you using a single or dual projector setup for 3D? If duals, make sure that the reflector color temperatures are the same. If not, it would look OK after awhile, but would be a total PITA when the show is over and you try to look at things without the glasses! It's always best to match them as if it was a "change-over" theatre.

>>> Phil

Posted by Greg Mueller (Member # 17) on 03-12-2003, 09:42 PM:

It's a single projector. Side by Side anamorphic. I've got the original lens for projecting and a Silver Screen on the way from the great white north (MDI)

Sam send me a note off line

Posted by Fred Georges (Member # 505) on 03-12-2003, 09:51 PM:

Dear Greg, You've got a cold mirror but, at 1K it wouldn't make any difference. Those StereoVision instructions really only start mattering at 2K & above and it's to protect the polarizers from burn up from the UV. The Marks Polarator & StereoVision Mirror box "fit" the AAII quite well for over/under. If you're doing side by side "House of Wax" etc. You can rig a much superior lens set up then the Stereovision all in one with those old B&L cokebottle Scope lenses they use. If you do it right you'll want to collect nothing but 3D. It's that much fun. [Cool]

Posted by John Pytlak (Member # 331) on 03-13-2003, 07:07 AM:

The dichroic coating on the reflector is there to remove the INFRARED (heat) energy from the light output of the lamphouse, usually with a "cut" for wavelengths greater than about 750 nanometres. As Richard notes, an additional dichroic heat filter that mounts in the beam and reflects the IR to a heatsink is added insurance for larger lamps.

It's also a good idea to remove the ULTRAVIOLET energy from the light, as it can cause dye fading after thousands of runs. Century used to have a "UVIR" filter that mounted behind the shutter.

Here are some tutorials on dichroic interference filters:

http://www.ocli.com/pdf_files/products/dichroic_coatings_uv_vis_apps.pdf

http://www.ocli.com/pdf_files/products/gen_info_infrared_filters.pdf

http://www.spie.org/web/courses/videos/vid97ose.html

http://www.broadwaypress.com/PDFs/LTSpdfs/LTSchpt09.pdf

Posted by Gordon McLeod (Member # 33) on 03-13-2003, 09:13 AM:

Those small 1K's can still ruin polarizers just as badly as bigger lamps Do not project white light through the system for any extended length of time

Posted by Fred Georges (Member # 505) on 03-13-2003, 03:40 PM:

[Eek!]

Whoops! Got my UV's & IR's mixed (Too much Bourbon). Thanks John for the correction. Assuming that this is the StereoVision one piece with anamorphic attachment. The polarizers are sandwiched between the adjustable prime & the Scope lens. As such the polarizers are much more prone to Heat damage then the front loaded mirror box attachments. I've never experienced Heat damage to the Mirror box type polarizers at anything under 2K but, yes I never run the lamp with a clear gate through them.

Posted by Greg Mueller (Member # 17) on 03-13-2003, 03:49 PM:

It's the backup lens "combiner" from StereoVision. One thing that is interesting is how to mount the StereoVision/backup lens separate from the anamorphic. Both have to be adjustable independently. I'm thinking a long 4" (dia) adapter, with setscrews at either end, since it has to go into a lens collar on the DP70 anyway

Posted by Gordon McLeod (Member # 33) on 03-13-2003, 10:17 PM:

The original split lens had a thumb nut that allowed the back split lens section to be rotated independently of the anamorph is the black tube was what the lens mount clamped in place
Also there is a set of bristol splines on the side that can modify the convergance if necassary

Posted by Greg Mueller (Member # 17) on 03-13-2003, 11:33 PM:

I now have two StereoVision lenses one is model 3518/.415 with a sticker on it that says "This Side Toward Operator". The orientation of the sticker would make this a side by side unit. I can find no thumb screws or any other adjustments on it but the black tube does come unscrewed, leaving an inner black tube.
The other has smaller lenses on the film end and it's sticker says the same thing but by it's orientation would make this an over under. No thumb screws etc on this one either and the black tube does not come undone

Posted by Gordon McLeod (Member # 33) on 03-14-2003, 09:41 AM:

If there isn't a thumbscrew there may e a set screw on it to lock down the back section

Posted by Greg Mueller (Member # 17) on 03-14-2003, 10:01 AM:

Here's a couple of pics I snapped of the two lenses. You can see the black labels that say "This side towards operator" The one on the left is the Side by Side and the one on the right is the Over/Under

Other side

Posted by Darryl Spicer (Member # 711) on 03-14-2003, 01:28 PM:

The over under lens adapter was used so you didn't have to use the mirror boxes wasn't it? We didn't have one of those for our over and under presentations back in the 80's. you just had the mirror box that attached to the flat lens. Didn't those also fill the screen properly were the mirror boxes never did?

Posted by Greg Mueller (Member # 17) on 03-14-2003, 01:41 PM:

"... The over under lens adapter was used so you didn't have to use the mirror boxes wasn't it?..."

I have one of those Paramount kits too and I think that the Paramount Over/Under film had a bigger line between the top and bottom picture so the mechanical interferance of the mirror box (where the mirrors come together) wasn't a problem. I think the earlier over under had a tiny line in between so the split lens was needed. I could be wrong.

Posted by Gordon McLeod (Member # 33) on 03-14-2003, 01:48 PM:

The number on the lens was the seperation .387 .425 etc
there were many different seperations on the over under stuff
The Paramount box did the best job of any and coud be used when flipped on its side with a compact serries anamorph to do excellent side by side. Also the paramount unit allowed for keystone correction of the overlap.
One problem with all 3d systems that are single film is that there is always overshoot that has to be masked off

Posted by John Pytlak (Member # 331) on 03-14-2003, 02:30 PM:

3D "Over-Under" format is specified by SMPTE 257-1998: for Motion-Picture Film (35-mm) - Stereoscopic Prints with Vertically Positioned Subframes - Projectable Image Areas

This standard specifies the maximum dimensions of the film image area intended for projection from a 35-mm motion-picture film using vertically positioned subframes for stereoscopic projection, and the placement of this area relative to the perforations and the reference edge of the film.

http://www.smpte.org/smpte_store/standards/

Posted by Greg Mueller (Member # 17) on 03-14-2003, 02:58 PM:

Unfortunately I don't have that publication. Is there a place to view it on the net? Do you know what year that was written/adopted?

Posted by Gordon McLeod (Member # 33) on 03-14-2003, 03:13 PM:

It was a standard that few followed I have loops for almost every 3d title since most did their own thing

Posted by Greg Mueller (Member # 17) on 03-14-2003, 05:14 PM:

I lust after your film loops

Posted by Michael Schaffer (Member # 1204) on 03-14-2003, 08:12 PM:

quote:
Where does one find an Align-O-Tron?
I performed a search and found my answer. I forgot that Greg invented the device.

Actually, Kinoton Germany already had a very similar alignment device. I broke the news to Greg at ShoWest [evil]

He broke into tears and said he hadn`t known about it at the time he designed the align-o-tron.
I thought about it for a moment, then decided I could belive him. After all, many of his posts suggest he has no idea what is going on in other parts of the world [Razz]

(Note I put a Graemlin here to underline the sarcastic/humourous nature of the post. I am also wearing the Mueller`s Atomics T-Shirt while I am writing this.)

The part about the Kinoton device is actually true. Still, I think the align-o-tron is a very clever parallel invention (seriously).

Posted by Fred Georges (Member # 505) on 03-15-2003, 02:08 AM:

Dear Greg, If you use your mirrorbox instead of the combiner lenses (Those lenses eat sooo much light and aren't exactly "High Rez") You won't fret the lack of alignment loops. I've found it's best to adjust to the actual film being played. I use a reel of the film to be shown and tweek to it. I've found that even with the proper loop you'll end up doing a touch up. The Paramount Mirror box IS the best to use for side by side as you can use the best glass before it and, you can fold both images into each other with minimal reflections and, as Gordon pointed out, keystone correction & the easiest to change polarizers. It made my experiments between linear & circular polarization a snap. But, the two easiest to use for over/under are the StereoVision mirrorbox and the Marks Polarator 2. The StereoVision is super easy to tweek on the fly and some of those pictures (Comin at Ya & Jaws 3D) don't maintain consistent over/under convergence over their length and do require adjustment. [Big Grin]

Posted by Gordon McLeod (Member # 33) on 03-15-2003, 09:41 AM:

I often use a reel with credits and align the verticle seperation until they over lap then use the loop to set the depth
Friday13th has probably the worst constant changing of verticle septeration with metalstrom coming a close second

Posted by John Pytlak (Member # 331) on 03-15-2003, 10:18 AM:

quote:
Unfortunately I don't have that publication. Is there a place to view it on the net? Do you know what year that was written/adopted?

SMPTE Standards are copyrighted materials, so you need to purchase them for a copy.

http://www.smpte.org/smpte_store/standards/

The CD-ROM is a good deal for any service organization, as you get all the standards, recommended practices, and engineering guidelines for motion picture, with a license to share among five users:

http://www.smpte.org/smpte_store/standards/cd_standards.cfm