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Author Topic: Focus/anamorphic test films? Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 05-06-2008 03:33 AM                        quote: Brad Miller making sure the projector is absolutely level via the flat lens before even considering making an adjustment to the astigmatism on the scope lens. How is the best way to achieve this? Is it good enough to just use the scope spherical lens or another longer focal length lens with a new and uncut 1.85 plate and assume the rectangle of the plate is true so then you can level the rectangle image you see on the screen either by a level or actually measuring the image placement. Or is there any place on the projector head that if you put a level you can get a reading that has enough "resolution" to get it perfect?  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 05-06-2008 10:46 AM                     You run PA35 through the flat lens and adjust it to your masking (the masking of which is easily verified with a level or tape measure). Since you are a changeover house, be prepared to intentionally skew the level due to keystoning, which at this point you have to eyeball it. Somewhere in the last few months I posted a lengthy set of instructions on how to setup and align a turret. I don't remember where it was though.  |  IP: Logged Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 05-06-2008 11:53 AM                        AFAIK, And I could very possibly be wrong but I always thought that after you de-focused the scope attatchment and then brought the horizontal lines into focus that you were focusing the prime lens, then when you brought the vertical lines into focus with the attachment you were focusing the anamorphic?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 05-06-2008 11:59 PM                     Frank, Ideally (and it is where I START)...you level the projector and then run a high precision target like 35PA (Schneider's test film will work too). If the lines are symmetrical on the screen and follow the masking, you are done. However, often you will find that is not the case. You then need to check the level of the drapes (masking) and if possible, get those fixed. If that is not immediately available, you will need to delevel the projector so the image is even and symmetrical on the screen. People's only point of reference are those maskings so absolute level is less important than having the image look right. I'm not saying one should gloss over getting everything level...that IS the proper way. Your eyes will play tricks on you, especially on multiple projector installations. Often you are above the center line of the screen so your keystone will be skewed...that is, the lines at the top of the screen will seem much more in keeping with the top masking than the bottom of the screen. The opposite would be true if you are projecting up hill. I use PC-Cine adapters almost exclusively to negate all of this in single lens machines. Many turrets will also allow one to shift the lens a bit (how much differs by manufacturer). Century offers lateral adjustment on their single lens machines and Simplexes may be adapted (or ordered) with the 35/70 upper lens guide to allow lateral lens shift. What ever you do...do NOT use the aperture plate as your guide...there is no guarantee as to how that hole was cut and what reference it has. Some plates are machined and will have more precise holes...others are stamped and "you get what you get." As to focusing anamorphics...Some Euro machines (Cinemeccanica comes to mind)...would put the anamorphic on a swing away attachment that would allow focusing as Louis describes. However, from his discription, Brad's and my techniques are pretty identical. Note, in the current 35PA target, there are for oval/circles...they should all look like circles when the twist of the anamorphic is set correctly. If you have astigmatism problems in your eyes...you may have difficulty using them but they are a tell-tale sign of how well you got it. Schneider's target also uses a mixture of ovals and circles. Schneider also super-imposed a grid to indicate relative keystone. Steve  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 05-07-2008 07:26 AM                     quote: Steve Guttag Ideally (and it is where I START)...you level the projector Hopefully not with any ole level... I highly reccomend the investment in a sensitive machinists level such as those made by Starret. These types of levels are the only ones sensitive enough to put any meaning to the term level. Mark  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 05-07-2008 08:49 AM                     I level the machine using the flat lens against a line relative to the stage floor since that is what the audience sees as a level surface or the auditorium ceiling  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 05-07-2008 10:40 AM                        Gordon, funny you should say that -- just a couple of weeks ago we were in the process of rerigging our side masking track and legs and I was trying to get the legs to hang straight, i.e., at a perfect right angle to the top and bottom masking. I used a laser level, then used a water level. When the instruments said it was perfectly perpendicular, we'd go back in the orchestra amd eyeball it -- it looked slightly off. We'd set it to look good by eye, and the instruments would say it was off. I went back and forth like this, eye and instruments and finally I got fed up and asked four other guys to help decide and when we agree with what we all said looked perfect, I set it by that. I went back to measure, and the levels said we were off. Too bad. It has to look good, not instrument accurate. The only explanation we could come up with is that perhaps the geometry of the top and bottom curve of the screen (it has a slight perspective curve) and the curve of the proscenium had some affect on the perception. Sometimes you just have to trust your senses.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 05-07-2008 11:52 AM                     quote: Mark Gulbrandsen I highly reccomend the investment in a sensitive machinists level There is definitely quite a bit of confusion here. I am with Steve that being level with the screen is of most importance on an alignment. A physical level is simply not needed.  |  IP: Logged

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