Film-Tech Forum ARCHIVE: Isco Optic Lenses

This is topic Isco Optic Lenses in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Joe Morris (Member # 1553) on 01-13-2003, 10:52 PM:

I have some Isco-Optic lenses for my screens, and I am having problems with focus and picture. I have an Isco-Optic Ultra Star Cinemascope lens with a flat screen. I'm having problems focusing the entire picture. It will either focus the top or the bottom, but not both. Also, when I play certain scope trailers, I get curved edges to my picture. I have run SMPTE film through my projectors time and time again to try to get them to focus and adjust correctly, but simply cannot get them correct. Any suggestions as to what the problem could be?

Posted by Joe Morris (Member # 1553) on 01-13-2003, 10:55 PM:

I've checked my projection angle and everything, the sides of the picture when playing trailers appears like this ) (

Posted by David Favel (Member # 1125) on 01-13-2003, 11:08 PM:

In the tips section there is an excellent piece on this subject. Try that first

Posted by Daryl C. W. O'Shea (Member # 1303) on 01-13-2003, 11:10 PM:

Just during trailers?

It would make sense if the sides were like this / \

Posted by Bill Mantz (Member # 754) on 01-13-2003, 11:23 PM:

I had that problem before but not with the sides of the scope trailers out of focus. Check the tension bands they might be to tight.
When ever the replace the tenstion bands this usully occurse

Posted by Paul G. Thompson (Member # 655) on 01-13-2003, 11:26 PM:

I never had any trouibles with ISCO lenses. Check your lamp alignment.

Posted by Mark Gulbrandsen (Member # 72) on 01-14-2003, 12:05 AM:

I never had any trouibles with ISCO lenses. Have your eyes checked! [Wink]

Mark

Posted by Joe Morris (Member # 1553) on 01-14-2003, 01:35 AM:

Believe me, I've double checked EVERYTHING. I've replaced the guides, checked the SMPTE, checked the level of the projector, and it still comes out ) (

Posted by Daryl C. W. O'Shea (Member # 1303) on 01-14-2003, 01:38 AM:

You say just the trailers?
How about the feature?
What formats?
Every lense or just one lense?
Did somebody try to take apart the lense?

Posted by Joe Morris (Member # 1553) on 01-14-2003, 01:44 AM:

Both trailers and feature. I have two Isco Ultra Star HD's on two screens and two Isco Ultra Star's on two more screens. I don't have problems with the flat lenses, but the scopes have curved sides, and curved tops and bottoms. It's the wierdest thing I've seen. I've never had a problem adjusting a lens before these.

Posted by Brad Miller (Member # 2) on 01-14-2003, 02:09 AM:

Ask your staff to see if someone has a digital camera that they could take a screen shot of this effect and upload it here so we can see. I really don't think this is a lens issue either. Isco makes damn good lenses.

Posted by Joe Morris (Member # 1553) on 01-14-2003, 02:12 AM:

I will take pictures of the effect and post it so you can see it. Is there a difference in lenses for curved and flat screens?

Posted by Steve Guttag (Member # 268) on 01-14-2003, 08:03 AM:

Have you focused your lens properly ? That is...run RP-40 with the anamorphic distance ring set to infinity...use your projector's standard focus knob to focus just the horizontal lines . Then use the anamorphic's focus ring to bring the vertical lines into focus.

Next...what is the focal length of your lenses? The lens wants a constant throw and a flat screen will not provide that exactly...it is normal for a slight pincushion on a flat screen. Scope is more noticable since it is more extreme.

If you are using an integrated anamorphic lens, it is going to yet nastier still...all of the integrated anamorphics use 4-element anamorphic sections (with the exception of the 3 different sizes of ISCO blue star integrated).

Steve

Posted by Pat Moore (Member # 380) on 01-14-2003, 11:59 AM:

Joe; Steve has the best suggestion -- start from scratch and focus the anamorphics as he describes. There should also be a small instruction sheet that came with the lenses describing the practice.

While Integrated Anamorphics aren't my favorite thing, I have never seen an ISCO pincushion an image like you describe. Are you sure the screen is physically flat? Sure sounds like something else is off-kilter here.

Pat

Posted by Kenneth Wuepper (Member # 1174) on 01-14-2003, 09:10 PM:

Hello Joe,

I am really confused here. I am under the impression that you have 4 screens. I understand that all of the flat images are fine although they are from two different style flat lenses.

ALL four scope images are pincushioned as you describe. Are all of the scope lenses identical?

Are these lenses a prime element with a spacer and then the scope (Anamorphic) adaptor on the front?

I have only seen this effect once and it was because the spacing tube was too long for the focal length of the prime lens. The proper tube restored the image. This would be especially true of short focal length prime lenses when used with too long a coupler.

What focal length are the scope primes? What focal length are the flat lenses?

KEN

Posted by John Walsh (Member # 168) on 01-14-2003, 09:15 PM:

Jut guessing, but exactly how far is the )( ? What dimensions do you see at the center and at the top/bottom.

Could someone have screwed the wrong prime lens on to an anamorphic adapter?

Posted by Joe Morris (Member # 1553) on 01-14-2003, 09:49 PM:

I will take pictures of my lenses, and also a picture of the scope trailers so that everyone can get an idea of what's going on.

Posted by Gordon McLeod (Member # 33) on 01-14-2003, 10:50 PM:

Since you are in Strongs home turf maby Pat or some one could drop over and have a look [evil]