Film-Tech Forum ARCHIVE: Laser Lens upgrade for Holmes portable

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Posted by Ken Layton (Member # 133) on 11-15-1999, 11:00 PM:

I was looking thru the physical specs of the Smart/CPI Laser Lens unit and it looks like the Simplex version should fit once all of the exciter lamp assembly parts are removed.

Then with a stereo solar cell it should able to give a nice stereo sound output to a processor.

Posted by Kelsey Black (Member # 126) on 11-16-1999, 01:29 AM:

I use the old exciter bulbs in my projectors (Century and Motiograph.)
I've been tinkering off and on for the past few months with trying to develop a "$5 solution" to a red light source. I've tried high brightness LED's, and I have attempted to use laser diodes (salvaged from laser pointers.)
I haven't had any success yet, although I have only hreally tested high brightness LED's (the brightest I've come across are 15000mcd) but even with that light level, I cannot get enough light through the slit to achieve anything even remote to Dolby level.
I haven't really tested with laser diodes as the last one I had got fried by my "regulated" power supply (oops) and shortly afterwards on a different project, the power supply was destroyed (yeah, I wish I had a schematic for it.)

Unfortunately, now that I have come across another laser pointer, and believe I have a good power supply, I am moving in less than 2 weeks, and will be forced to abandon my efforts in this. Has anyone on here made any such attempts?

on a different subject, I have come across a few Cyan dye soundtracks. the first one that caught my eye was "The Story of Us" in which the soundtracks on all formats faded out almost completely towards the reel change at the end of reel 2. and clearly, it was printed in cyan dye, much like the high magenta soundtracks are.
Since then, I have been able to pick out which prints are with cyan, magenta, and "standard" soundtracks.
So, while I was screening this print, I paid particular attention to the soundtrack at this point, and to my amazement, the faded out cyan soundtrack was just as clear and noise free as any other point in the movie. however, I would not have liked to run this print with the old sound system we had on this projector, as it had no type of noise reduction whatsoever.

Posted by Gordon McLeod (Member # 33) on 11-16-1999, 09:08 AM:

The five dollar solution faces too problems

1 enough brightness to achieve dolby level
2 Even slit illumination

The latter is a problem on most of the Laser scanner type
They typically have a bell curve like response to slit illumination
The Jax light so far has been the best econo solution

Posted by Bruce McGee (Member # 131) on 11-16-1999, 10:13 AM:

Is this "cyan" upgrade going to cost me more than my whole projector cost? If so, I guess I will be sticking to the old back-up lights.

One minor point:

These machines (Holmes) are 50+ years old. There are alot of them around, according to my E-mails, so, why is everything out the roof price wise?
The way things are going, I will never find magazines for my second machine.

I am getting tired of 20 minute shows, then an intermission while I rethread....

Is anybody here living in an under $100,000 house like me? I bought mine in 1986 for $16,000. It is appraised for 89,000 now. It has 1000 square feet of space, fully A/C'd, rewired, replumbed, roof, etc. One room is dedicated to the film collection. The rest of the house is not.

The point I am trying to make is this. I is poor! I am selling off a bunch of 16mm school projectors as quickly as I get them checked and lubricated, but it doesent go far with 35mm. I have one hi-dollar 35mm feature, and the rest are average stuff. I got lucky with accessories. $50 splicer, $90 electric rewind (in 16mm-paid $60 for the 35mm shaft)
My job is slowing for the winter, so money will be tight. Anybody (or all) in this mess? Oh yeah, I aint married, so no 2nd income to help out.

I love this hobby, but prices are insane. This is why I use Sony junk! When I got it, I worked for SEARS and got a good discount!

I'll stop now.

Posted by Stefan Scholz (Member # 147) on 11-16-1999, 12:04 PM:

Cyan is a problem, mention the factors even light distribution and enough light output in total. JAX is a solution, but still is listed at 500+ $, more than affordable for private use. Somebody running a commercial theatre can easily affor this.
I remember having seen cyan tracks on WW2 films, in 16 more often, than on 35. Photoelectric cell were coated with a red paint, and the system worked. Trying to use a red filter on your bulb, as I understand, will not work properly. You would have to use a bulb of approx 1kWatt rto gain sufficient light output.

I have seen a solution with a standard 3mW laser diode at Technicolor labs, they had a standard 1950's type Phillips Cinema soundhead, where they focused the beam onto the slit lens, and claimed it works quite oK. Maybe you'll have success with your laser pointers.
Most reasonable laser diodes with slit lenses have anything but even light distribution. The converters which give even distribution are available from special companies supplying the medical and telecom field, and I have had a list featuring prices in XS of $ 1k per lens. We have been quite satisfactory with a standard line generator laser (8 degrees line) from Vector Technologies, which had illumination uniformity of approx 1.5 - 2 dB.
Disadvantage: about US 600+ without barrel or mounting. Laser claas 3A, which normally means, that you have to built a lighttight enclosure around your projector, which shuts off the laser, the moment you attempt to open the enclosure. So this solution may not be legal... but works. Compared to tungsten bulbs the noise floor is about 12 dB higher, but otherwise, using monochromatic light, you pick up less scratches from the film.

My brother, working in mediucal laser engineering at our medical university, told me about a possible $ 50 solution, but so far never came over with his knowledge. As soon as I know, I would tell about it.

Posted by Kelsey Black (Member # 126) on 11-16-1999, 12:37 PM:

Actually, I have never used any filtering of any sort in conjunction with the exciter bulbs.
This is a small town theater that is barely making it, so we do not have the "commercial theater" budget. heck, I have a hard time trying to get the manager to be willing to spring for some film guard (no, I don't have media cleaners... and I'm hoping to get one off of ebay, so anyone out there reading this had better not bid against me! haha!)
But since I got my first (and last) bottle of film-guard, the stuff is in my blood... so it's something that I *must* have. (no brad, it's not chemically addictive)

I have a fair amount of experience with lasers, as I have been building them and working with them as a hobby for years. the only *good* one I have right now is a 10mW He-Ne, which I wouldn't part with even *if* I could fit the laser head in the soundhead.

so, my point is, a Jaxlight is out of the question.

And yes Bruce, there are even some theaters that are on a tighter budget than you are.
The theater itself is probably only worth no more than $150k especially considering that most of it isn't up to code (no fire sprinklers, emergency lighting, etc.) and it is in such shape because the "landlord" will not do any of the repairs, upkeeps, etc. necessary, and also IN THE CONTRACT. It would be so nice if someone could buy it outright from them and properly maintain and manage it. *hint* *hint*
so anyways, the current managment is probably going to dump the operation on some poor unknowing soul as soon as I leave (I'm the reason we still have equipment running) and then the whole thing is going to go under. Meanwhile, I need to find a job that pays well where I am moving to. If anyone out there is in west Salt Lake City area (Magna especially) please let me know, especially if you can get me a good job projecting or doing tech work. *sigh*

now back to your regularly scheduled mundane posts.

Posted by Gordon McLeod (Member # 33) on 11-16-1999, 05:56 PM:

The natural colour films all had cyan tracks for which a theatre had to use a selineum sulfide cell (green dot) and a red dyed excitor
The $600.00 for a jax light amortised over a year is probably costing less than the operattional cost of a xenon lamp. The bottom line is that in a bout a year there will prbably be no choice if a theatre wishes to exhibit 1st run product. It is still less than the cost exhibitors had to fork out in the fifties to get anamorphic lens.
The other option is the 150grand dlp

Posted by Bruce McGee (Member # 131) on 12-20-1999, 11:57 PM:

Kelsey: I have gotten several replies like yours. I should consider myself lucky to have all that I have and consider myself fortunate to have discovered the web and linked-up with all you people.

Its too bad that the job slows this time of year. BUT, It IS nice to work a little less during the Holidays....

Merry Christmas to everyone, and have a happy new year!

Posted by Jeff Stricker (Member # 224) on 12-21-1999, 07:04 PM:

I've been tinkering with using an ultra bright red LED on a simplex SH 1000 soundhead. It appears that the small point source of light of the LED is too small to be correctly imaged, thus creating the uneven slit illumination on the film. I guess the optics are designed to image the entire exciter filament.

Since this is just a low budget home tinkering project, I'm thinking of making the LED more opaque by doing something to make the plastic appear cloudy. Of course this will scatter the light and make less light available.

Oh well. Merry Christmas and a happy 2000

I've been enjoying all these great posts ... a great source of info to this beginner and frustrated tinkerer.

Posted by Bill Purdy (Member # 202) on 12-22-1999, 10:29 AM:

I know that people are getting tired of the whole "Dye Track" subject, but for those who want to know a little more about it, we have posted a piece on our website ("Why Dye Tracks?") that may help your understanding.
http://www.componentengineering.com/nftechupdate.html

This is may help you to understand why your well meant experiment wasn't successful.

------------------
Bill Purdy
Comonent Engineering

Posted by Ken Layton (Member # 133) on 12-22-1999, 10:58 AM:

It would be nice if Component Engineering or Kelmar came out with a reverse scan kit for the Holmes and DeVry portable 35mm projectors. At the very least, I think that Ultra-Stereo could make a JAXLITE for these machines.

Posted by Jeff Stricker (Member # 224) on 12-22-1999, 06:24 PM:

Bill, thanks for the post and link to the dye track article. That gives me a much better idea of the amount of red LED energy that is required to do the job!

Posted by Bruce McGee (Member # 131) on 12-23-1999, 12:12 AM:

One more question:

Are there really enough of the Holmes and DeVry projectors out there to warrant the costs of designing a laser system for these machines? Are many Holmes still in service in theaters? DeVry's?

Is their running speed as smooth as "real projectors?" Or am I just concerned for nothing?

I've read some real horror stories here about digital!

Posted by Bill Purdy (Member # 202) on 12-23-1999, 10:37 AM:

You are correct. The problem is largely one of economics. There are just not enough potential sales to justify the development costs.

As for the Holmes, I had a pair of these rascals many years ago and I did modify one of them to take a good "solar cell" by milling out a little pocket in the casting on the right side of the trap. Then I made a little bridge piece onto which I had cemented a mono raw cell (with RTV). However, I never worried about the exciter. Why couldn't someone remove the old socket and cobble together a mount from somewhere else that would accept a Jaxlite?

I know even less about the deVry, but I did once try to make a holder for a stereo cell but had to abandon the project because the slit lens was one intended for a 16mm projector and therefore would never have scanned the full 35mm track. Were they all that way? I don't know.

It's a tough problem, I know, and we have all recognized the need for an inexpensive solution, but it doesn't seem to be in the cards. From my conversations with Jack Cashin of USL, I have some idea of how much his Jaxlite has cost him not only in dollars, but in frustration as well. How about an LED manufacturer who agrees to make your design and then can't be bothered with a mere quarter million dollar order?

------------------
Bill Purdy
Comonent Engineering

Posted by Ken Layton (Member # 133) on 12-23-1999, 11:06 AM:

My vote then would be for ALL soundheads to remain with good old reliable exciter lamps. To hell with cyan.