Film-Tech Forum ARCHIVE: Barco 23B picture shaking after lens replacement

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Posted by Michal Matys (Member # 8614) on 03-26-2018, 09:34 AM:

Hi all,

I have recently swapped lens in two Barco 23B projectors. The lens I was using before, was 1.2" 1.45-2.05. New ones are 1.2" 1.25-1.83.

New lens is much "longer and bigger" than the previous one, I do not know how this could be related, but after the lens replacement, there is a visible shaking of the picture when displaying test pattern.
I have swapped pump with other projector, most of the fans, turned off the exhaust fans with no help. I have also checked the lens holder, the lock nuts for scheimpflung adjustment are tightened, everything seems in order.

My question is, did any of you ever experience this? What was usually cause of picture shaking in your Barco projectors? Maybe this is coincidence, but since it is related to two projectors where the same lens was installed, it is strange. Dont know how the lens could affect this tho.

Thank you
Michal

Posted by Marco Giustini (Member # 4544) on 03-26-2018, 10:28 AM:

Yes, this is common with Barco B machines. It is the way the lens mount is designed.
Make sure your Scheimpflug (I love this word!) is fully tightened - but make sure you know what you are doing if you play around it!!

B's lens mount feature an antivibration spring/bearing at the top. Make sure the bearing actually touches the mount and the spring is set for maximum pressure. You will need a headtorch to confirm whether the bearing fully touches the metal.

Also try decoupling the extract fan from the chassis - just hold it a few mm away from the chassis with your hands should work but make sure you do it safely, wearing safety equipment at all times.

If nothing works, you may need the new "enhanced" stabilising device that replaces the basic bearing at the top of the lens mount. I've also seen a unit requiring a whole new lens mount as the lens was literally wobbling in its socket when fully fitted.

Posted by Steve Guttag (Member # 268) on 03-27-2018, 06:58 AM:

I've found that using the InVision lenses often will result in an image shake. Depending on the projection angle and outside stimuli (vibrations), you will see a substantial image movement.

Barco sells a lens stabilization kit that will substantially address the problem. Why they have not incorporated it into production still escapes me. The current system, as described above merely puts downward pressure on the lens mount but still allows unrestricted lateral vibration as well as pitch variations as the lens moves fore/aft. The improved upper mount applies a linear bearing like the ones on the bottom of the mount that effectively restricts the lens mount from vibrating laterally or pitching. It can only move in/out for focus, as it should.

Posted by Alan Gouger (Member # 543) on 03-27-2018, 10:42 AM:

"Moving Image Technology" offers a nice solution.

http://www.movingimagetech.com/product/lens-stabilizer/

Posted by Jerry Axelsson (Member # 3175) on 03-27-2018, 11:16 AM:

Instability in the exahust fan of the Barco projector causing the longer lens to move more than the previous one?

Posted by Mark Gulbrandsen (Member # 72) on 03-27-2018, 11:21 AM:

LOL! You never have this kind of issue wiith any of the NEC's, granted scheimpflug is a lot bigger pain to do on them.

Mark

Posted by Sean McKinnon (Member # 612) on 03-27-2018, 02:19 PM:

Your right Mark, you only have the issue where after the projector has warmed up for 20-30 minutes the entire focal plane changes and you have to refocus the image.

Posted by Brad Miller (Member # 2) on 03-27-2018, 02:40 PM:

I would highly question that MiT lens stabilizer. And what exactly happens when formats are changed and a lens rehome is performed? I'll bet damage happens to the lens mount.

That is probably only useful for those "premium" ( [Roll Eyes]

) screens with no masking that only have one lens setting and all lens files are removed from all macros.

Posted by Sean McKinnon (Member # 612) on 03-27-2018, 03:07 PM:

There is much debate on whether it causes artifacts or not but you can use resizing to move the image on the chips instead of moving the lens not that it makes the "lens stabilizer" a good idea.

Posted by Kirk Futrell (Member # 5006) on 03-27-2018, 03:43 PM:

According to the MiT website :

The lens is supported by non-marking nylon transfer balls that allow the lens to continue to rotate and move in and out for focusing and zooming.

If installed properly it seems like it shouldn't cause a problem.

Posted by Mark Gulbrandsen (Member # 72) on 03-27-2018, 09:30 PM:

quote: Sean McKinnon
Your right Mark, you only have the issue where after the projector has warmed up for 20-30 minutes the entire focal plane changes and you have to refocus the image.

Then you're definately doing something wrong! 334 NEC's installed and no issues like that at all. Many S2 NEC are now 7+ years old. The Invision lenses do not work in them! They only work correctly in the 3200 and 3240.

Mark

Posted by Steve Guttag (Member # 268) on 03-28-2018, 07:33 AM:

Don't forget about the 20% of your light you flush away when using an NEC or the complete lack of lens accuracy with the NEC (repeatability). Then again, Mark, I fail to see when one is seeking help with a product of brand A, you feel the need to bring up brand B. It isn't a solution or help, it is just dickish. Suffice to say, whatever brand product one has or likes, there are the good points and the bad points. What is dumb about the "B" series Barcos is that THEY HAVE THEIR OWN SOLUTION but fail to use it.

Posted by Mark Gulbrandsen (Member # 72) on 03-28-2018, 09:17 AM:

I disagree Steve and the fixes offered for the Barco are childish at best. Where is the manufacturer and why havent they stepped up to address the issue properly themselves?

Mark

Posted by Steve Guttag (Member # 268) on 03-28-2018, 10:23 AM:

What do you disagree with? Little of what I said is matter of opinion. I agree that Barco should have addressed this issue, especially since they have a proper solution.

Posted by Brad Miller (Member # 2) on 03-28-2018, 01:36 PM:

quote: Kirk Futrell
According to the MiT website :

The lens is supported by non-marking nylon transfer balls that allow the lens to continue to rotate and move in and out for focusing and zooming.

If installed properly it seems like it shouldn't cause a problem.

Again, what happens when the lens is rehomed??? Every manufacturer's lens design needs their version of rehoming every once in awhile. Image shift on the DMDs won't stop that.

Posted by Sean McKinnon (Member # 612) on 03-28-2018, 02:22 PM:

You can say that Mark but we have other NEC installs without this issue. Of course you can say every manufacturer has a bad unit now and then but then again we have many many barcos with no lens issues either.

Posted by Steve Guttag (Member # 268) on 03-28-2018, 03:02 PM:

BTW, the part number for the improved upper lens stabilizer is R9856618

Posted by Sean McKinnon (Member # 612) on 03-28-2018, 03:42 PM:

FYI- Barco has also changed the procedure for seating lenses. Apparently too many people were having a hard time seating the lens properly before engaging the locking mechanism so now they are advising to close the locking lever then slide the lens in until it "clicks" in. [Roll Eyes]

Posted by Marco Giustini (Member # 4544) on 03-28-2018, 05:23 PM:

that's not new in my knowledge, Sean, I was taught that many years ago. Still, I have seen myself mounts where the locking mechanism had gone loose and the lens itself would wobble if grabbed from the front and pushed around a little.

Posted by Mark Gulbrandsen (Member # 72) on 03-29-2018, 11:20 AM:

quote: Sean McKinnon
You can say that Mark but we have other NEC installs without this issue.

I wish I could claim some of my sites had that problem, then I could do some service calls!! Another hint: The 3200 and 3240 use an entirely different lens positioning system than the 1200 and 2000 use.

Mark