Film-Tech Forum ARCHIVE: laser or reverse scan LED to read old variable density mono?

This is topic laser or reverse scan LED to read old variable density mono? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Brian Dooda (Member # 3941) on 05-20-2007, 12:39 PM:

Is one better for reading variable density and older mono tracks? I work in an archive and we are still holding out with exciter bulbs because we have a large collection of older mono prints. The past few years too many cyan tracks have come through and its time to compromise. Booth restrictions don't allow for penthouse readers and we are not in a position to change projectors from our Century SA's.

Posted by Stephen Furley (Member # 1277) on 05-20-2007, 12:55 PM:

I've run a few VD tracks on red lasers, and they sounded ok to me, but others have reported problems. I have no experience with reverse scan readers.

What do you mean by 'Booth restrictions don't allow for penthouse readers'? Are you talking about physical restrictions, e.g. insufficient height to fit them in, or some srt of pollcy rections, e.g. fire regulations for handling nitrate? Is there really no way you could do this, as having both types of readers would seem to be the best option in your situation.

Posted by Gordon McLeod (Member # 33) on 05-20-2007, 03:04 PM:

A Black and White VD track should have no issues with it other than possibly noise since the high freq response is so extended
There have been some colour VD tacks that may have issues

Posted by Brian Dooda (Member # 3941) on 05-20-2007, 03:27 PM:

The restrictions are physical as we certainly don't have the ceiling height for 6000' reels and a penthouse and probably don't have room for 2000' and a penthouse.
-Brian

Posted by John Hawkinson (Member # 1135) on 05-20-2007, 03:51 PM:

I thought the recommendation for this situation was to go with BACP's reader that supports both red LEDs and IR LEDs, so you can swap if need be.

Not that I've seen people do this, but I've always wondered if you can't offset the penthouse and the upper reel arm, e.g. the penthouse is in front of the reel arm, rather than under it, so the film comes off the reel, runs forward to the penthouse, and then back to the projector.

--jhawk

Posted by Scott Norwood (Member # 30) on 05-20-2007, 04:22 PM:

See the pictures of the Museum of Fine Arts in Boston. They can fit 2000' reels and penthouse readers by tilting the upper arms back behind the penthouses. That might be an option if the lamp exhaust isn't in the way.

The issue with the BACP option is that the reader needs to be re-focused when switching between IR and red LEDs (though this is what I am planning to do in my home screening room, since I don't mind having to re-do the A-chain once in a blue moon).

Posted by Sam D. Chavez (Member # 1841) on 05-20-2007, 04:46 PM:

Scott,

The amount of difference in focus is very small and is considered by most to be of no consequence.

You can optimize focus for one or the other. If you can stand the tedium, you can split the difference, but I have a number of customers who set for the Red and are OK with being very slightly out of focus on the odd occasion of running on the IR LEDs.

Posted by Steve Guttag (Member # 268) on 05-20-2007, 05:04 PM:

Sam,

I have found the focus difference to be more than small. That is, if you are flat out to 12KHz on one(+/- 1dB)...don't expect it to even get to 8KHz on the other. Now some may feel that being flat on the red reader will be good for modern tracks and being out a bit on older tracks will hide their noise since tracks before Dolby had questionable HF response since the systems of the day really didn't do very well above 8KHz anyway.

Posted by Lindsay Morris (Member # 1430) on 05-21-2007, 04:29 AM:

Well, my ears maybe deceiving me but when I run a compilation of cyan, Hi magenta and older VD tracks I really cannot pick any difference... apart from the obvious poorer freq response of the VD stuff.

At the outdoor the Century has been converted using the ACL laser unit and I maintained the capability of running white light if ever needed by leaving all the original exciter stuff in place.
I modified the exciter bracket the ACL laser is mounted on so that I could break the incoming exciter DC power and send it thru a 3 term adjustable regulator unit to give a precise and stable supply to the laser. Then at any stage I can slide out the laser unit on the holder and slip in the white light backet back in should ever I need it.
Every session at the outdoor features an old Newsreel which are often VD or older VA tracks and those are just run in mono. Even some of the older OZ classics I have recently run have sounded fine on the laser and I did not have to go back to white light at all.

In my home screener which uses an RCA 1050 head driving a Super Standard projector head (not Simplex but an Aust made head from South Australia and long since out of business).
I use the screener primarily to check my first reel complation of News and trailers plus first couple of reels of the feature I am about to play (on 6000 footers as trying to fix stuff ups at the outdoor is a pain on the Eprad MUTT reaching over the spools trying to find and fix outa frames etc... much easier on the bench at home BEFORE the public see the error).
The RCA 1050 I modified with a Lumiled running at about 800mA and it works fine and to test that I made up a reel of all sorts of tracks of everything I could find... mono, stereo, VA VD... you name it whatever I could find I spliced together and let it rip and had a listen.
The processor is NOT a cinema processor but a domestic NAD 910 and it is smart enough to switch to mono for mono stuff and into stereo as needed. Apart from the obvious change between mono and stereo the sound quality seemed much the same on all track types. If I switched off the L & R and Surr amps and just let it go on Centre only the only difference I could hear was a little distortion coming from the older tracks... some of the stuff I was using was also a bit shrunken etc and very splicey.
I just optimised both machines for Cyan and what comes goes thru that and is pretty hard to pick any difference.
So would not really worry much at all apart from running mono as mono and probably like I have to do on the Eprad Starlet I use manually switch between mono and stereo tracks as needed.

Posted by Richard May (Member # 2627) on 05-21-2007, 08:25 AM:

We just ran a festival with prints as far back as 1920. Some were variable density. We had no problems at all with our reverse scans readers.

Posted by Steve Scott (Member # 630) on 05-21-2007, 08:43 AM:

I've heard a few older density tracks played with our Kelmar LED, to no ill effect.

Posted by Steve Guttag (Member # 268) on 05-21-2007, 10:24 AM:

The biggest thing I've noticed from some density tracks is "whomps" at each edit (the sound system should be high-passed for mono anyway...but unless they are magenta colored, there were no problems I've noticed.

The worst offenders of red readers are colored tracks, particularly in the Dolby A era. In fact, a good one to use to hear the ills is an original DTS Buzz and Bill reel from 1993/1994. They have horrible cross mod distortion on a red reader.

Steve

Posted by Scott Norwood (Member # 30) on 05-21-2007, 10:35 AM:

Steve/Sam--assuming that both the IR and red LEDs are available, should one use the IR type for showing everything except for cyan tracks, or should the red LED be used as the "normal" type except for tracks that sound bad with the red reader?

Posted by Richard P. May (Member # 3598) on 05-21-2007, 12:18 PM:

Speaking from a restoration lab standpoint, there is no problem running density tracks with red LEDs. We are using Kineton readers, and much of our work involves printing from original density tracks. They play perfectly well.
The one problem that can occur is a color print with a density track. If the print is processed conventionally, with hi-magenta color in the track, it will filter out much of the red LED light, resulting in either very poor or no sound. I was told this happened recently at the Alex Theater in Glendale CA, running "Desk Set".
For the most part, when a restoration is done, a new track negative is made. This results in a modern VA track, so no problems.

DM

Posted by Steve Guttag (Member # 268) on 05-21-2007, 07:23 PM:

That all depends Scott...if you run the red reader with a low current to prolong the LED life, you will inherently also increase the noise of the system since the solar cell is sensitive to the IR spectrum. Thus if the IR and the visible red LED are driven to the same lumen levels, the signal will be stronger on the IR system which will need less preamp gain and thus less noise in the system. As such, an IR reader will be superior for all tracks that are not optimized for red light (all except cyan or high-magenta). Due to how the light leaves the LED and goes though the film, both types of LEDs will be noisier on damaged film than a traditional white light system.

A big plus in IRs favor is that it is VASTLY more stable than the visible red LEDs...which still vary from batch to batch greatly. IRs tend to stay at a nice level for a very long time.

Steve