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Discussion Starter · #1 ·
I recently received the ISCO II lens for my Nec lt150 projector. After several hours of trying to adjust the attachment last night, I still have what I would describe as massive pincushion distortion, especially on the top of the image, and slightly on the side (the bottom is straight).


I realize that AVS and some others had warned about this distortion (and indeed the instructions with the lens indicate that some distortion is inevitable), however, I was led to believe that the distortion is very slight, and can be eliminated from view by overprojecting the image 1/2" (drmyeyes had stated as such).


I would like to know how I can reduce the distortion and whether the intensity of the distortion may be a function of the projector I am using (i.e. could it be that the lt150 and ISCO II may not be compatible?). I'm hoping it's simply my technical inexpertise.


I have already contacted Alan and Jason at AVS and they have been extremely helpful in their response. I was wondering if anyone else has encountered a similar problem with an ISCO II and lt150. Or if there are any other suggestions or "tricks" that might help optimize the lens. Thanks.
 

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I have an ISCO I with a DILA. The tilt of the lens moves the pincushion from top edge to bottom edge. Also with the ISCO I, the longest throw you can get is best. I am at approximately 2.0.


------------------

Jim Nissen
 

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I can't imagine that the lens won't work with this projector. Try sitting the lens in front of it, loosening the set screws, and tilting the lens until the distortion is least. Depending on the angle to your screen and the offset of this particular projector, the lens may wind up looking like it's not aligned with the projector's visual axis.

Until you get more facile adjusting the lens, you can set the lens and projector on a common adjustable shelf, and change the height of both together by raising or lowering the front of the shelf, avoiding having to realign the lens at different projection distances.

The whole process only takes a minute, when I move the projector back to fill my 2.35 screen.

 

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I too have an ISCO-1. Make sure your exit image is as small as you can get it. Zoom *out* all the way(making a small image),then center exit image on the ISCO. This will take care of much of the distortion.


Jaime
 

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JFreeman,


I also have the ISCO I, but I have played briefly with the ISCO II, and found (at least with the D-ILA) that the pincushioning was minimal, but of course "minimal" is a perception, based on expectations.


The ISCO lens should be as close to touching the projector's internal lens.

The main adjustments for pincushioning are first centering the lens, by turning on the projector and adjusting the lens height and right-left orientation relative to the internal lens. Then (and this is a big one) adjusting the up/down-side/side pitch so that there is a balance of the of pincushioning on all sides.


Then on the back collar of the lens there is a slider adjustment with a locking button that alters the rotation of the lens. This adjusts the sides to be mostly up and down, but also affects any tendencies for one corner to distort more than the others.


Rather than trying to set the top or bottom exactly flat, it's important to balance the pincushion between all four sides, as having one or two perfectly straight edges will push out the distortion on the other sides, looking worse overall.

Plus, once you get it centered, it's easier to do smaller fine tuning adjustments.


I don't know the LT150 in particular, but even though the D-ILA does have zoom capabilities, it has a large lens which is normally an issue with external lenses, and the ISCO II is larger than the ISCO I lens, so it should work with your projector.


-Dean.


[This message has been edited by Dean McManis (edited 06-12-2001).]
 

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Jfreeman,


I wonder if the relatively short throw ratio (1.63) of the LT150 that is the problem. This means the image expands relatively rapidly and it may just not fit within the ISCO's diameter.


Have you gotten anywhere with this? I have a personal interest, as I want to do an RP installation, and the shorter the throw the better.


Thanks


------------------

Noah


[This message has been edited by noah katz (edited 06-21-2001).]
 

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Discussion Starter · #8 ·
You may be right. I still have not been successful in minimizing the pincushion distortion to acceptable levels. I had a guest from the forum over at my apartment a few nights back and he commented that he had seen the ISCO II used with a Seleco 200 (which has a long throw lens) and that there was hardly any distortion.


It appears that the only way to solve my problem is to mask off the screen for both 1:78:1 images, as well as 2:35:1 (the pincushion is very annoying on letterboxed images). I have not done this yet, but plan to this weekend. If that fails, I may have to give up on the ISCO II, since I happen to rather like the lt150.
 

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Hi,


Is it possible that any of you with the ISCO I lens

could post some pictures of the projected image, so one can see how much the picture is distorted as I am considering buying one :)


Thanks,

Thomas.
 
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