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I recall that a Scandanavian company had developed an automatic focusing device for 35mm film projectors that optimized focus by using a CCD camera to view a small portion of the screen image and adjusted focus to maximize fine detail in a fourier transform of the image data.

Steve

About using binoculars to check your focus: How do you know your binoculars are in focus!?

You should be able to focus the binoculars on the screen perforations.

In commercial theatres the situation is often ALL the reasons you guested at, and then some. A projector can't focus itself. Or if the guy who eventually is sent up after a complaint is not trained to know what to actually look for when focusing, it can be a worthless exercise. We all assume because we have been doing it for years that focusing self-explanitory. But just think of the process you go through when you focus. If you reallly think about it, it's fairly complex. You are looking for specific visual elements that are easy to judge. It isn't just a matter of twisting a knob and guessing at it. But guaranteed, that's pretty much all some concessions kid will do. And an element that can't be ignored here is the person's eyesight. How good or how bad is it? I know plenty of people who don't wear eyeglasses or contacts who have very poor eyesight. It may be one of these who is sent up to the booth to fix a focus complaint.
For many years I have worn an Olimpus Binocular around my neck almost all of the time I am in the booth; it's the best way to focus. Using them makes focusing a piece of cake and there is never any question when you are in -- it is like you are standing 5 feet from the screen. Doesn't matter how good or bad your eyes are. I only need these, however when I an in the smaller venues. In the big 2500 seat house, my XLs have focus scopes -- they are mounted on the side of the lens holder and you look down into it and you see a portion of the screen magnified -- a sort of built in monocular on each machine. Bet you guys haven't seen that in awhile. Why they are not part of every projector design is a mystery.

Barring a focus scope on every projector, they at least should have a pair of binoculars in every booth and teach those booth attendents to use them when they go up to correct a soft picture that a seeing patron has complained about.

Frank

Every FIVE minutes the movie must be checked in every auditorium for focus and sound anomalies. We would not tolerate anything less!! The exception of course was that projectionist may take the time necessary to allow for proper threading and starting of shows and breaks/ lunch etc. If there was no break or a movie to thread...then they would HAVE to pace around the auditorium every FIVE minutes. Along with booth checks we also had a policy of physical auditorium picture/sound checks to say that projectionists were expected to enter an auditorium every 1/2 hour or and double check the picture and sound quality from the perspective of the movie goer. This practice worked tremendously. Theater managers were able to record or log less presentation complaints throught the chain as a whole. Thank God for hard work paying off!!!!!

As far as a simple problem as focus however, the movie patron should note this once a complaint has been made to the management.
Proper focus occurs when the lens is at the critical distance to the film <or focal point>. In my chain I would teach this method to focus.

Since the focal point is a critical distance....a projectionist must go from one extreme of unfocus passing the focal point and reaching the other extreme of unfocus. In this way and only in this way can one trully notice when the picture goes from bad to good to bad again making it easier to notice the true point of best focus. Then he/she can trully make a note as to when the picture was at its best possible point of focus. A move goer should notice the picture get out of focus....pass the best point then get out of focus again only to return to the correct spot. Psychologically this tells the movie goer that a TRUE effort has been made in attempt to focus the picture.
I have had great results with this simple method and thus complaints have greatly decreased as a whold. Lastly, I feel projectionists must be tested periodically as to what good focus looks like....The notion that perfect focus is obvious to everyone is taken for granted to much and is part of the problem. Do projectionists really know what great focus looks like? Sometimes it remains to be verified and I have run into this quite more often than I would care to admit. I happen to be 20/300 in my right eye....and I would bet that I can achieve better focus than your typical projectionist anyday. Sad isn't it? For me or for the projectionist? HAHAHA!!!

For the record, both my eyes are around 20/350, but are corrected to 20/15 with gas-permeable contacts (20/15 is "better" than 20/20 for distance -- razor sharp).

Where I used to work, we had a ceiling-mounted D-ILA projector in a large multi-media demo room. It had remote-operated focus. The best method of focusing for me was to stand very close to the screen and get the individual pixels as sharp as possible.

Some might argue that you should slightly DEFOCUS the digital projector, so the pixel pattern is not as obvious.