Barco 32B Focus issue

[Jay Glaus]

Hi guys,

Been racking my brain at an issue I’m having on my 32B. I used to have a razor sharp picture. On the green preview screen, the text was so sharp that you could have sliced salami on it. Lately it has not been quite so sharp.

It’s not a scheimflug issue, already tried that. It’s perfectly even. Cleaned both sides of lens, cleaned port glass. It’s barely noticeable and honestly probably the only person that is going to notice it is me. But I know what it used to look like.

there is a very slight soft edge around the text. So slight in fact that you don’t even notice when you are into the actual preview or movie, only on text. I’m just trying to figure out why I can’t get a perfect razor sharp focus on it anymore.

I’m running an In-vision lens that is 8 years old. Only thing I notice about it is when you duck around the front of the machine, there is a slight haze in the lens. It’s not in the front element, it appears to be the element behind the front. I wouldn’t call it foggy, it’s not that bad. It just looks every so slightly hazy. This machine has run a 7kw bulb for almost all of its life and I’m thinking perhaps the heat of the beam is finally taking its toll on the lens.

Anyone have any ideas or think that could be it?

[Leo Enticknap]

Scheimpflug would only be a possibility if the soft text was softer on some parts of the screen, but not others. If the softness is uniform from top right to bottom left, and vice-versa, then the Scheimpflug (focus uniformity) is OK.

I'd suggest hooking a wifi access point to your management LAN, then standing right next to the screen with a laptop and moving the focus back and forth. If you simply can't get it razor sharp at its sharpest point then either, as you suspect, tens of thousands of hours of a 7kW bulb throwing all that heat and UV through the light path has taken its toll on the lens, or something is out of whack in the light engine (prism?).

Have you checked the convergence? Likely not an issue, because if you're judging using the "Focus Green" test pattern, then you're only seeing the output from one DMD, meaning that converging all three won't affect it. But a convergence test pattern might reveal soft focus on one of the colors but not the other two, which would suggest a light engine problem rather than a lens problem.

Alternatively, do you have another screen, also with a B series projector, that you can swap a lens from, to see if the fault moves? If so and the fault moves, that would confirm your suspicion that your lens has gone bad.

[Jay Glaus]

Leo, I’m suspecting the lens. I actually have a spare lens in the booth that’s never been used I’m going to try at the end of the night. Convergence is spot on. Touched it up about two months ago and checked it last night. I’m really leaning towards that haze in the lens being the culprit just barely making some edges soft.

[Leo Enticknap]

At the risk of stating the bleedin’ obvious, remember to do a home and return after putting the spare lens in (this was hammered into us at Barco school: home and return every time a lens is swapped). If the spare is the exact same model as the suspect lens and you don’t see fhe softness, that’s pretty conclusive: a bad lens. If you do, the problem is likely upstream in the light path.

[Jay Glaus]

Update... so I put the new lens in. Yes, the lens did make things sharper. I’m sure that old lens took some decent heat over the years. But I think I have a deeper issue, when I put the focus pattern up I noticed my Scheimpflug is out.... again.

Here’s the whole timeline of when my problems started with this machine:

Opening weekend of Halloween Kills, on Saturday I noticed when I started my convergence was way out. The opening scene where it says “OHIO”, in white looked horrible. Friday night it was FINE. That night I converged the machine. While I was doing it I noticed my bottom left corner was out of focus, so I Scheimpfluged it and remade my screen and lens files. After that I had a beautiful and sharp picture.

About a week or so later, I noticed it was just a hair out of focus. I just chalked it up to maybe I hurried a little making the lens file so I touched it up and re-saved the lens files. I was certain this time it was perfect. I even threw the convergence pattern up and double checked, convergence was still spot on. I’ll also point out I had no format changes. Everything at this point has been Scope. The lens has not been told to move at all.

Last night when I started the show, everything looked great, part way through I got a call that the picture was out of focus, and it was. It was fine when I started!!! That is when I tried to focus it and couldn’t get it as sharp as it used to be, but I did get it better. And when I saw the haze on the lens I started thinking lens. Again, still no format changes.

Tonight, I put the new lens in. I did get it sharper than it was, but when I was checking it I saw something that made my heart sink. Scheimpflug is out again. It’s not unwatchable, but I have no where near the uniformly focused image I had before. I don’t understand it. I tightened everything up when I was done doing it last time. I’ve Scheimpfluged many a machine before and never had an issue. It should not come out that fast. Convergence is still spot on.

I don’t understand what is going on with this machine. All my problems started the night my convergence went out. Any ideas for me?

[Steve Guttag]

It's tough to figure out why it suddenly changed. The lens could certainly have aged and with repeated hot/cool cycles of a 7KW lighting system, I can easily believe that elements within the lens have moved a bit (Schneider lenses of the film era were notorious for getting loose elements).

As for migrating Scheimpflug, well, the Barco "B" lens mount (for the S2 projectors) was not their finest hour, for sure. It is shock mounted from below, which allows for the lens mount to tilt/skew. Their first correction of this was inadequate (put a set of ball bearings at the top to ride on the assembly as it focuses. Unfortunately, this became the "standard" mount. With the very heavy InVision lens, it will let the mount sag and, depending on your lens, it could set up a harmonic resonance that lets the lens bounce because you now have a heavy overhung lens and the ball bearing assembly fighting one another with a near equal force. Barco makes/made a kit part number R9856618 that uses a linear bearing at the top of the lens mount that prevents sag yet allows for precise focus adjustment. This will improve the "B" projector's overall focus because the lens will no longer be able to vibrate, which can show up as a softer focus too.

For whatever reason, Barco gets obstinate about their issues. This is one of them where what they are shipping remains problematic though they offer an improvement! (The other biggie is their signal backplane connectors that are notorious for having more connectivity/noise issues than anyone else's and hence more reseats than anyone else).

The upper lens guide you WANT to have looks like this (this is a cartoon artist's conception version):

BarcoLensStabilizer.jpg


What you likely have is this garbage:

BarcoOldLensStabilitizer.jpg


BTW. If you are running a 7KW lamp, you'd be an ideal candidate for switching to laser. Either with an LLU kit or moving to the SP4K series. 7KW lamps combine expensive with short life (compounding the expensive part). Lasers will age things less (less heat, no UV), cut your electricity way down and also end the perpetual lamp changes. I'm not big on switching to laser for machines under 4KW but for 6KW and up, it can make a lot of sense. We have a drive in that runs a 6.5KW lamp and due to their short season, I can't make the cost justification for the laser upgrade (they only use 1 lamp a year...they could run over 10-years before hitting an LLU upgrade...give or take electricity)...but if yo are doing multiple swaps of lamps a year, then it would make sense.

[Leo Enticknap]

Whether or not the LLU route makes sense is also informed by the age and condition of the rest of the projector. If it's done 30-40K hours of 7kW lamp on time then the backplane, cards, fans, and light engine will also have been on the receiving end of all that stressful heat cycling, and all you would be replacing is the light source. A drive-in I service put the Appotronics laser upgrades into both their DP2K-32Bs in February, their main motivation being to boost the light level. They also negotiated new light engines as part of the deal, conscious that these projectors were 8-9 years old at the time. However, they have still had to contend with all the non-light source maintenance issues that you'd expect with projectors of that age, including a new backplane on one of them recently.

[Steve Guttag]

Shoot...I change out backplanes regularly and, fortunately, they are not a high price part (relatively speaking). I would absolutely recommend a light engine cleaning/refurbishment. Cinionic does have a program just for that. If it is done as an RX, it can be a rather dramatic improvement as most will not notice the day-to-day decay of such parts. As to the LLU...we found that if one does it on year 6 or 7, you can make the argument a bit better...however if the lamp size is large, then that age can shift up a bit since the lamps (and electric) costs are so dramatically higher than say the 2KW range (the most cost effective lamp). Cinionic also offers extended warranty up to 13-years when a LLU is installed.

[Leo Enticknap]

Backplanes are not an expensive part, but they do require a tech to swap out (major disassembly, so this is not a job that one of the theater staff would be able to do in 99% of cases). The risk of one failing and a Friday or Saturday of shows being lost while a tech gets to the site should be taken into account when deciding between upgrading a Series 2 projector to laser, and buying a new Series 4. The theater's location is something to factor in. If it's a 10-plex situated 20 minutes' drive from the service vendor's shop, that's an entirely different proposition from a single screen drive-in in Dead Skunk Junction, ND, with a bare minimum of two days for a tech to get out there.

[Jay Glaus]

I’ll check the lens guide, but I’m pretty sure I have the bottom one. I’m wondering if my mount is getting weak and starting to sag. In all the years I’ve had this machine I’ve never had an issue with focus or Scheimpflug. Other than a sagging mount, I can’t see how else Scheimpflug would be coming out so quickly.

Maybe simply swapping that lens was enough to move it out more.

If that is it, in theory, I’m hoping replacing that guide would be enough to fix my problem, and I’m not needing a whole new lens mount.

[Jay Glaus]

Or am I misunderstanding that to get that better guide I have to replace the entire lens mount?

[Jay Glaus]

Also as far as laser goes, sure I’d love to. My issue is my projector is too close to the patrons. From my understanding the code is 15’ away from anyone, and people walk right in front of my projector about 6 feet in front of it. I’d have to raise my booth up a little to make this work, maybe add a half of a floor up. I’m still toying with the idea of how to make it work and lose the least amount of spaces possible.

[Steve Guttag]

Installing the better upper stabilizer does not require changing any other parts at all. It's a bit of a PITA (particularly the first time) because you are working in a space where you can't quite get your fingers or tools in and you are going to have springs and things wanting to shoot all over the place (fall down into nooks). You also should have a disposable allen key because one of the acorn nuts is to be removed and that allen key is working against a thread locker (its not a big key so it can get bent in the process). We've changed out quite a few. There is a whole "groove" to it all (moving the lens mount forward and inward as you get various parts in the best position for removal/retrieval. Having long needle nose pliers to hold onto a spring or acorn nut can go a long way to not having to look for it later.

The first one...allow 1-1.5 hours...the second one should go in under 30 minutes.

[Jay Glaus]

I’m going to order one. I’m praying this fixes it and my headache ends. It was making me start to question my sanity.

[Steve Guttag]

It won't hurt, that's for sure. I forgot another item that I recommend. it isn't essential but it sure ensures that one gets things situated correctly. It is a torque driver. The torque specification is .25Nm +/- .05Nm. And, you are setting two screws to this amount and if they are not set identically, it will apply uneven pressure to the linear bearing. I use a Wera 05074770001. It is probably more than you will want to spend for just 1 system. I did my first ones without it but found it required a bit of "touch" to get the torque just right on the two screws so that everything ran smoothly and was rock solid.