ISCO ultra star - red - In pursuit of sharpness - A tutorial

[dr5chrome]

So I have been in the photographic field since 1985. My work in shooting has been mostly still. My only experience with cinematography has been numerous cinematographers who shoot film for an art service I provide, in its 22nd year as a service. 

I am making a transition back to shooting after putting my cameras down in 98. I got the strange idea to use anamorphic lenses  for a shooting project by studying old projection lenses adapted for still shooting... So here I am. In all my years I had no notion of anamorphic [guess you can teach an old dog new tricks].

Scouring the web is how I ended up here. Thus far it has been trial and error. This project requires Sharpness!  The 1st lenses I bought were ISCO. 

To shorten the story, I picked up a RED ultra-star. My research indicated that this lens was the sharpest [Modern anamorphics are out of my price range]. 

My tests indicated a sharpness issue with this scope. Was it just like that? Image samples online indicated no, It was a tack sharp scope.

There was a post some years back on the KOWA and focus tweeking, but the ISCO red wasn't the same and I could find little info online to service these scopes. 

For normal cine use I suppose my scope was ok, it was just out of focus. This condition was bothersome for me. I could find no one to provide the information I needed to adjust this scope, nor could I find anyone to service it. 

After a few off the cuff replies, someone replied by email that the rear element might need adjusting, then went on to another discussion. I took this brief comment seriously, because I never heard it before. I am mechanically inclined, so I took the risk and dismantled the scope. The following is that adventure. My dangerous tinkering was successful and I post it here in case it helps someone else with the same problem - this info is not on this forum that I could find.

First I took the front focus ring off. It is held in my a few small screws in the focus tube. Be careful when you slide the tube off. There are a small springs and ball barrings. 

 

The focuser dial is held in by a large retaining ring with a set screw. The focuser ring screws down off one of the brass guide plates. NOTE - The focus issue was not in this location on this scope, but should one need to put new grease in you would simply unscrew where the small guide brass plates are.

I am fairly certain that  focus issues with this ISCO involves the rear element alignment. This was the case with my lens.

On the rear there are about 5 small set screws. Loosen them all up, but don't take them totally out [very small - easy to lose]. When loose the rear element holding dial becomes free. I discovered that this rear element is very critical in the focus, of not just this scope but likely most if not all scopes. The rear alignment is very critical for focus. [Ill assume that when manufactured this setting is dont on some fancy divise to set the focus.] 

At first I thought I might have ruined my lens until i realized that the placement was very crucial. Be sure you have a small screwdriver in hand with your camera on live-view, and make sure your adapter clamp is the kind you can slide the scope off easily.  With the rear element loose, move it very slightly. Put it on the taking lens w/live view. Taking it on and off moving it either direction until the sharpness is tack-on. Set the closest set screw when the live view is sharp. Remove the scope and tighten the other set screws - Reassemble the scope.

 

I hope this helps someone out.  Thanks for reading.  Dave Wood

[Henchman]

This is how you you do it on the gold Isco as well. 

What I dud was leave about an inch gap between the taking lens and scope. Just enough so I could get a, toothpick in one of the holes on the rear element. And I slightly turned it.