Film-Tech Forum ARCHIVE: Adjusting Focus

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

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Posted by Ian Bailey (Member # 1752) on 01-14-2005, 06:18 AM:

I find adjusting focus the hardest thing in operating a 35mm projector.The problem I have is knowing the best spot in the projected image to look at when trying to adjust focus.I realise now that this problem would not be as difficult if i had top quality lenses but at the moment I have to be content with what I have got.Any suggestions here would be very helpful.

Posted by Brad Miller (Member # 2) on 01-14-2005, 06:30 AM:

*Get a pair of binoculars and use them to focus on the grain. (Be sure and focus the binoculars on the performations of the screen in a bright area first though.)

*Try and hit optimum focus off-center right. That will put you not at the edges of the frame, nor at the center. Generally that's a good target to achieve uniform focus on most setups.

Posted by Jeremy Fuentes (Member # 2135) on 01-14-2005, 06:51 AM:

Or you could just focus it the best you can, ask 5 people if they think its focused, and if 3 out of 5 think its focused, then that should be good enough. [thumbsup]

Posted by Thomas King (Member # 2745) on 01-14-2005, 07:34 AM:

In my experience, one man's focus is another man's blurry mess. I suppose that's where having a non-flat focus comes in handy; you can tell one guy to look at one side of the screen and another guy to look at the other!

Posted by Bill Enos (Member # 440) on 01-14-2005, 05:41 PM:

A rock thru and back to focus on a bright scene will give excellent results without binoculars. The old guy who trained me in the booth said that if I needed binoculars to focus, somebody else should do it.

Posted by Phil Hill (Member # 371) on 01-14-2005, 06:20 PM:

Gosh Jeremy, that sure would work! Especially with all the drunks and dopers around... "Yesh, huld it! Pefleck!"/"Kewl dude, duh colurs R sharp, K!"

Brad has the best solution.

Posted by Scott Norwood (Member # 30) on 01-14-2005, 07:58 PM:

I like to focus on closeups of peoples faces, since there's lots of detail that can be seen if the image is properly focused, and faces are almost invariably photographed in proper focus. With modern film stocks, it's impossible to see grain from the booth without binoculars.

Posted by Peter Mork (Member # 1336) on 01-15-2005, 04:17 AM:

Especially good if Clint Eastwood is in the movie. Failing that, I like tree bark or stone walls.

Posted by Pete Wolla (Member # 1581) on 01-15-2005, 09:38 AM:

i was wondering if the projector is off center (as in running one projector from a change over converted to a platter)will that greatly affect the focus side to side. also what would affect the focus from top to bottom of the screen. i try focus off lettering but it seems to vary by screen position

Posted by Peter Mork (Member # 1336) on 01-15-2005, 04:50 PM:

Projector position doesn't matter that much, as far as focus goes. Where problems arise is in the gate - the "staging area" so to speak, where a tiny variation in the distance from film to lens makes a big difference. There are lots of reasons why you might have problems - anything from crud on the runners to misalignment of the trap - hard to diagnose from here, but removing the trap and cleaning it is a good place to start. Sometimes the solution to problems like this is to add shims (spacers) under the runners to change the angle of the film plane. I've done it, but it takes a lot of trial and error.

Also, maybe you just need better lenses.

Posted by Gordon McLeod (Member # 33) on 01-15-2005, 07:21 PM:

peter said "Projector position doesn't matter that much, as far as focus goes"
sorry that is dead wrong especially with short focal length lens

Posted by Pete Wolla (Member # 1581) on 01-16-2005, 07:26 AM:

thanks for the input i do clean the runners every show (only 3 per week)it may well be the lenses.

Posted by Ferdinando Innocenti (Member # 2477) on 01-16-2005, 11:20 AM:

Where I have a remote focusing device, I use a simple RF receiver connected to the turret and a transmitter I hold in my pocket. When I need focusing, I can go just near the screen to have the best focus as possible.

To have the best focus installing the lenses, I think it’s really important lens-shifting, to correct the wrong position of the projector.

Ciao
Nando

Posted by Kevin Markwick (Member # 2698) on 01-16-2005, 05:27 PM:

Someone told me years ago that you should always focus on the actors eyes as this is where the audience naturally concentrate
their attention.

It's always worked for me.

Posted by Steve Guttag (Member # 268) on 01-16-2005, 10:19 PM:

Sorry, Bill. I think whom ever told you that (if you need binoculars to focus you need someone else) is an idiot. It all depends on the theatre...if you have huge screen a mere 50-feet away...you shouldn't need assistance.

If you have a 20' tall screen 100-feet away...you would need extraordinary eyes to properly focus that.

Binoculars are a tool (or s screen-scope on a Simplex) which can give you a much better result than just the naked eys. With binoculars you can focus down on the grain of the film.

Anyone that has done serious darkroom work has used a focusing apparatus that amounts to having a microscope to focus the enlarger precisely on the paper and that is right in front of you. It is all a matter of how precise you are trying to be.

Steve