Film-Tech Forum ARCHIVE: Focus Issues

This is topic Focus Issues in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Chase Pickett (Member # 5975) on 05-07-2011, 12:15 AM:

Ok I'm not sure what I'm missing here, but here are all the equipment specs. Strong Millennium with a Highlight 2 console. 5k bulb, and ISCO optic Ultra Star cinemascope lenses. The print playing in this house is Thor (scope.) So what may be the cause of the top 1/4 of the screen looking like a shit smear, while the rest of the image is perfectly in focus? Other than cleanliness, a cracked lens, proper bulb focus, Throw distance set incorrectly, or a mis-timed shutter? All of which check out. It's also worth noting that the print is shedding like a Motherf***er, but the bands aren't too old or too tight. The Bulge in the film as it is entering the front of the aperture looks as normal. I also don't think it could be a film issue as all of the trailers, snipes, and reels of the feature are like this. Any help would be MUCH appreciated.

Posted by Randy Stankey (Member # 64) on 05-07-2011, 12:50 AM:

Does the problem still occur when the flat lens/aperture are in place?
If so, you have eliminated the lens as the problem.

Can you bring the top part of the picture into focus at all? Adjust the focus so that the bottom blurry but the top is sharp? (Or mostly sharp.)
If so, you have eliminated the turret, focus mechanism and general gate alignment.

A shedding print often indicates misalignment in the gate. If you inspect the film with a magnifying glass can you see scuff marks or damage on the film?

Are your studio guide rails properly tightened and correctly aligned?

Is your film shoe properly installed and aligned to the trap?

Remember, the image of the film is inverted with respect to the screen. The bottom of the picture on the film, as seen from the operator's perspective is the top of the image on the screen. Therefore, look at the part of the film at the bottom of the aperture. I'll bet the film is bulging in the gate.

It could be because your studio guides are not parallel such that they are closer together at the bottom than they are at the top.

Also, the trap and the intermittent sprocket need to be precisely aligned.

All of this can be checked with a trap alignment gauge or a steel ruler.

Don't forget to look at your intermittent pad shoe.