Film-Tech Forum ARCHIVE: C/S Image not in Middle of Screen

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Topic: C/S Image not in Middle of Screen

Ian Bailey
Master Film Handler

Posts: 317
From: Nambucca Heads, Australia
Registered: Jun 2003

posted 12-26-2003 05:40 PM

Hi Guys
This is my first Post(the first of many).I am new to Film-Tech and new to the industry(1 year).I am an owner,manager,film handler,Box Office person,choc top maker,cleaner etc etc.I congratulate the Film-Tech boys on a very informative and helpful site.
We have very similar gear in two of our auditoriums(both auditoriums are the same size)-Simplex 35 model 1050 projector with TU2000 turrets.The only difference being the C/S lens-one has a 1.8 scope lens and the other has a 1.7 scope lens(both have the same anamorphic).Since taking over we have never been able to get as sharp focus with the 1.7 lens as we can with the 1.8 lens,and from what the staff have told me this is a problem they have always had.I purchased an SMPTE Test Pattern loop and ran it through the 1.7 lens and found the image to be central on the screen in W/S but a fair distance of to one side of the screen in C/S.The aperture plate was obviously never cut very well as the image can be seen on the top and bottom masking and on the side masking which the image tends to be pointing towards.The way I see it as the C/S image is not central on the screen we will always have trouble getting sharp focus.Any ideas on how i can improve this situation?-due to my lack of experience I have not been game enough to swap the lens complete with each other to see if the fault is in the lens.

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Adam Martin
I'm not even gonna point out the irony.

Posts: 3686
From: Dallas, TX
Registered: Nov 2000

posted 12-26-2003 06:26 PM

I'm sure others will be along shortly to tell you how to adjust the lens offset on that particular turret.

Check this page to learn how to properly focus anamorphic lenses. Be sure to check out the other items in the Tips Warehouse as well.

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 12-26-2003 10:42 PM

Your turret is out of line and assuming you don't have issues with seeing the edges of your aperture on screen, whoever cut the plate doesn't know how to do it properly. I am going to give you basic instructions on the assumption you are authorized to do this and have a general knowledge for this.

STEP 1:
Remove the aperture plate.

STEP 2:
Remove your flat lens.

STEP 3:
Turn on the projector and xenon. You should see a "bullseye" on the screen that is centered. If not, you need to adjust your lamphouse so that it is. (Read the manual)

STEP 4:
Put your flat lens back in and run the PA-35 test loop on screen. Make sure you can focus plenty far in and out in both directions with the focus knob. If not, you need to loosen the lens in it's mount and physically move it until you can. Otherwise you could be running a film one day that is embossed and find you run out of focus control.

STEP 5:
Is the projected image level? If not, adjust your console so that it is.

STEP 6:
Take a brand new aperture plate and put it in. Verify with both lenses you don't have any spill over onto the masking. You may need to make some adjustments (described below).

STEP 7:
Run your PA-35 loop with the flat lens in place. At the top of the turret there is an allen wrench bolt that adjusts your "up/down". Line this up so the aperture has equal amounts of shadow at the top and bottom.

STEP 8:
Now remove the aperture and rack your framing control until the picture is centered vertically. Be extra picky about the PRECISE vertical position.

STEP 9:
Between the two lenses are two screws you can turn with a short flat headed screwdriver. Adjust the one closest to the lens until the image is centered left to right.

STEP 10:
Flip to scope and adjust the up/down and left/right controls WITHOUT touching the framing control! (Note: the scope up/down allen screw is at the bottom of the turret.) Get them perfect to the masking in all directions. Do note that you may need to loosen the lens in it's mount and physically rotate it so that it is level. (Often installers don't physically level the console so the flat is crooked and the scope ends up being skewed. Tip - it is easier to make a loop out of a scope trailer that has side matting for a flat movie and to ensure those vertical "pillarboxed" lines are straight vertical than it is to use the PA-35 loop and check to make sure the horizontal lines are perfect.) This is also a damned good time to set the focus on your anamorphic. Doing so after you cut a new aperture plate can screw up the sides of your freshly cut plate. Adam posted a link to it above.

STEP 11:
Put the scope aperture back in and verify that you do not have any bleed over into the masking.

STEP 12:
Remove the aperture and flip back and forth several times to make DAMNED SURE you have things perfectly centered vertically and horizontally. I mean it, flip back and forth several times.

STEP 13:
Cut your new aperture. This is a whole different book.

Bear in mind these are basic instructions and does not get into things like whether your lateral guide rollers are properly centered or things like using a laser to make sure the turret is truly square to the aperture. Those things are absolutely a job for a tech, but since I see so many theaters where the turrets are not properly adjusted BEFORE the apertures are cut, I figured I would list the basics here.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 12-26-2003 11:11 PM

It is better to align the centering of the framer with scope lens in as the top and bottom is easier to centre
Level the console with the flat lens so that horizontal lines are parralel to the top and bottom masking
Switch to scope and adjust the anamorphic so crossed lines are at right angle
Then go and cut the plate

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