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As you move focus, does the focus point sweep across the screen? If so, the film is not perpendicular to the optical axis of the lens. Check the gate and lens mount alignment.

If the focus point spreads out from the center as you rack focus, the film is cupping in the aperture. Try adjusting gate tension, and be sure the film path through the gate is not misaligned or "pinched". Another factor here may be excessive radiant energy or hot spotting in the gate. If the focus improves as you reduce power, heat is likely involved.

Focus will be more of an issue with very short focal length lenses, especially those under about 40mm, because they have less "depth of focus". If you have plenty of light, consider a lens with a smaller f/number or internal stop to get better depth of focus. The newer lenses from Schneider or Isco usually have much better field flatness than older or off-brand lenses. If your lens is over 20 years old, use it for a paperweight, and get a lens of modern design.

If the problem is only in scope, be sure you have adjusted the distance ring on the anamorphic adapter to minimize astigmatism. See the "Focusing Anamorphics" section in the Film-Tech "Tips".

Ideally, you should be able to resolve 80 line pairs per millimetre in the center of the screen, and about 56 in the corners. Anything less than 40 lp/mm is unacceptable.

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Loosen the studio guides and shove them as far apart from each other as they will go, then tighten the screws back down.

It could be anything...

It can be your lamphouse alignments (less likely but certainly has caused what you describe).

The film is getting pinched in the trap (studio guides, are likely as is crud built up between the guide(s) and runner).

Poor grade lenses, particularly on short focal lengths. If the problem is only on one format, say Scope, then you are closer to your problem. Setting a scope lens is often misunderstood...the Tips section here on Film-Tech tells an excellent way of setting the distance ring. If you are using B&L anamorphs, you have to constantly tighten/loosen the locking ring AS you adjust the distance ring so as to make it just snug until you find the best setting; then tighten securely.

While changing the gates/traps over to the SA style is certainly an option and they will project the film better, it won't necessarily fix your problem. And as others have stated, it can be a bit pricey. Off of the top of my head, you would need the trap, gate, trap bracket, and light shield.

Steve

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Yes. I have done it to one of the very troublesome H heads in one of our booths. The only thing that will be required to do will be to cut new aperture plates, as the SA trap seems to have a slightly different centerpoint in the aperture plate slot.

" Other than the new kelmar turrit conversion kit that I hear good things about, how much would new or used parts cost to convert it?"

A new gate/trap assembly, complete with one undersize flat aperture plate cost us about $700. You will also need an SA-style light shield for behind the gate and aperture plates for any other formats you intend on showing on that machine.Used should be much less, and I am not sure of the Kelmar turret kit's price.

Good Luck!

Aaron

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