Film-Tech Forum ARCHIVE: Failsafe doesn't like B&W film

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Posted by Peter Mork (Member # 1336) on 04-15-2007, 11:31 PM:

About eight months ago we swapped four of our old failsafe/cue detectors for some Component Engineering FM-35s, the type which use an infrared beam to detect film presence and motion. (The ones they replaced were the primitive foil-strip-makes-contact-with-ball bearing variety, and if you've ever been stuck with those, you know how unreliable they are.)

Am I happy with the change? Yes and no - among other things you sure gotta keep the infrared thingies spotless or they won't see the film, and you can't just run a Q-tip over them; you must unscrew the mounting and pull the optical assembly out to do it well enough to work again.

But leave us not get into a rant. Here's the latest wrinkle: last week for the first time I ran black and white film through one of these, and it wouldn't accept it. As soon as the color trailers passed through, the "presence" light popped off and the automation shut down as though there were a film break. Nothing I could do would make it recognize the film, and I had to run each show of that print by manual override. Nuts!

Tried it with a different piece of film; an old B&W trailer: same problem. But it has no trouble with color prints. Tried it on the other FM-35s and they ran it without complaint.

I should also note that on two of the four units including the cranky one, the "motion" light never comes on yet the film runs anyway. Automation is a Kelmar 2035. (Come to think of it, why do you even need a "presence" detector - if the film is moving it is by definition present, no?)

I see nothing in the manual that suggests there's any way to do a sensitivity adjustment on these, so what do you recommend?

[ 04-16-2007, 12:43 AM: Message edited by: Peter Mork ]

Posted by Frank Dubrois (Member # 3042) on 04-16-2007, 12:46 AM:

We've had several B&W films and never had a problem with our Component Engineering FM-35's. Perhaps it might be in your automation? As far as cleaning goes, we really don't have to clean them at all. I think in 4 years, I've cleaned two of them, but that was because I was trying different things to solve a problem (which dirty sensors were not it). I find it hard to believe that its the FM35's.

Posted by Chris Slycord (Member # 4239) on 04-16-2007, 12:56 AM:

The point of the presence sensor is to not allow the projector to start when nothing is in the projector; namely, when the presence sensor fails.

And it's entirely possible for your film to be noticed as moving by the motion sensor but not properly aligned so that the presence sensor fail. That way, it avoids having a misthreading.

Posted by Frank Dubrois (Member # 3042) on 04-16-2007, 01:03 AM:

Perhaps the older B&W trailers and film is on a different kind of stock than the new film/trailers?

quote: Chris Slycord
And it's entirely possible for your film to be noticed as moving by the motion sensor but not properly aligned so that the presence sensor fail. That way, it avoids having a misthreading.

I'm not quite sure I understand that. How can film be noticed as moving if film isn't detected as present? If the film isn't sitting correctly on the rollers of the FM35, it won't be detected. Step 1 is to detect presence, step 2 would be to wait for motion. If step 1 isn't satisfied, then I don't think the failsafe will allow itself to even look for motion.

Posted by Peter Mork (Member # 1336) on 04-16-2007, 01:05 AM:

quote: Frank Dubrois
We've had several B&W films and never had a problem with our Component Engineering FM-35's. Perhaps it might be in your automation?

How so? Far as I can see, the automation only does what the failsafe tells it to.

quote: Frank Dubrois
As far as cleaning goes, we really don't have to clean them at all. I think in 4 years, I've cleaned two of them, but that was because I was trying different things to solve a problem (which dirty sensors were not it). I find it hard to believe that its the FM35's.

That's interesting, because I've several times had them fail to detect film at all, and solved it with a good cleaning.

These were used units, by the way, and I'm starting to wonder if the guy who sold them to us didn't just fob off a bunch of returns.

Posted by Frank Dubrois (Member # 3042) on 04-16-2007, 01:11 AM:

Ahhh....used. Well, in that case, its very possible that they are bad. We have had 3 of these items decide to work one show, then completely stop working the next. Its rare, but it has happened. The only reason I pointed out your automation is because I assumed the FM35's were new and didn't cooperate well with your automation. Knowing that they are used, I would suspect them. It would be odd that they work fine with color film though. How many do you have and do all of them dislike B&W film, but work ok with color?

Posted by Monte L Fullmer (Member # 2797) on 04-16-2007, 01:21 AM:

a more simplier reason could be that b/w stock isn't as reflective (absorbing the LED light) as color stock is being that the emulsion for B/W stock is almost a non reflective in nature whereas the color stock emulsion is more of a dull sheen reflection in nature.

Try this trick then - put a layer of clear tape across the emulsion of the B/W stock for the sensors to pick up the reflection of the LED emission. See what goes here then.

good luck - Monte

Posted by Frank Angel (Member # 248) on 04-16-2007, 01:36 AM:

I don't work with automation very often and then only the old electro-mechanical type of sensors, but just out of left field, let me ask, since the system reads reflectance, does the manufacturer specify if the sensor wants to see the emulsion side of the film or the base? Seems to me, the base would have much more of a fixed reflectance value than the various kinds of emulsions between types of film. Obviously that sensor is seeing (or not) a marked difference between the color film and the b&w. There probably wouldn't be nearly the kind of marked difference between the two different types of film if the sensor were "looking" at the base side. Could it be as simple a fix as threading it flipped?

Just a thought.

Posted by Pete Naples (Member # 761) on 04-16-2007, 01:38 AM:

Peter,

Were those FM35 new?

Years ago I came across this issue with them, basically the earlier FM35s are blind to true B&W film, there is an easy cure, you swap the IR Emitter/Detector head for a new one. IIRC the newer type have a blob of red paint easily visible to the operator. CE were doing them as an exchange for a small charge.

Posted by Chris Slycord (Member # 4239) on 04-16-2007, 01:42 AM:

What I was getting at is that the motion sensor could easily be just detecting that there is something moving past but that the presence sensor determines that the film is properly aligned in the roller.

Like in our projector it can fail because the sensors got dirty. But if I just turn on the motor and let it continually go, it sometimes still notices motion but not the presence.

Posted by Peter Mork (Member # 1336) on 04-16-2007, 02:48 AM:

quote: Pete Naples
...basically the earlier FM35s are blind to true B&W film, there is an easy cure, you swap the IR Emitter/Detector head for a new one. IIRC the newer type have a blob of red paint easily visible to the operator.

Ah, sounds like you may have nailed it. No, they were used and of unknown vintage. I will check for that paint blob - where is it exactly?

Posted by Pete Naples (Member # 761) on 04-16-2007, 04:42 AM:

A picture is worth a thousand words.

Excuse my rather crude effort with MS PAint, but I think you'll get the meaning.

Posted by Steve Guttag (Member # 268) on 04-16-2007, 05:20 AM:

The sensors AND the groved roller ar changed in the updated version. Make sure it has the red paint spot on the sensor. Compre the groved roller to the ones that work okay. You will see that the newer ones have larger slots and the end of the groove is chamferred. All of this helps the sensors "see" the film better.

Posted by Brian Long (Member # 2964) on 04-16-2007, 10:30 AM:

Peter,

Both Pete and Steve are correct. We upgraded the optical sensor and roller because of the black and white film stock. Please note that you must use the new roller with larger grooves when using the upgraded optical sensor.

The part number for the optical upgrade kit which includes the upgraded optical sensor and roller is FMPU-35. If you contact our office, we can get these out to you as soon as possible.

Thanks,
Brian

Posted by Pete Naples (Member # 761) on 04-16-2007, 11:13 AM:

Steve, Brian.

Yes, now you mention it I remember there being a new roller as part of the upgrade kit! I last dealt with these about 10 years ago, I can scarcely remember what I did yesterday, so it's little wonder I forgot that little detail.

Posted by Peter Mork (Member # 1336) on 04-16-2007, 04:59 PM:

Thanks, guys. I will check it next trip in. ("Good German", the B&W print that caused the trouble, was moved into a different house so it's no longer a pressing issue.)

I mentioned in passing above that in two of our four FM-35 equipped setups the "motion" lights never come on but the film runs anyway. Why would this be? I think they were installed properly. The LEDs could have failed, but come on, that never happens.

Posted by Scott Norwood (Member # 30) on 04-16-2007, 07:32 PM:

Hi, Peter.

For what it's worth, we have FM35s at the Embassy (vintage 1998) and they work fine with B&W prints (we had the "Mafioso" reissue recently). They don't seem to have dirt issues, either, and generally work quite reliably. I can't remember the last time there was a missed cue.