Film-Tech Forum ARCHIVE: Align-A-Tron 101 - How to use with a Century/Monee Turret?

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Posted by Matt Close (Member # 996) on 02-04-2003, 02:38 AM:

I am shortly to receive my Align-O-Tron from Greg, and my mind is dancing with the wonderful improvements I hope to make .... however.... I got to thinking, with a Century/Monee turret system (The one currently pictured in Brad's 'Strong Turret Tips' thread) and all it's various adjustments, how could you 'really' be sure that your lens holder is in true 'square' alignment with the centre of the film-trap? Surely you would have to check this before even starting to play with lamphouse alignment... yes?

As far as getting a centre spot to aim at, most suggest using a aperture plate with a hole .... but how do you know the aperture plate holder is adjusted dead centre? .... I thought of perhaps threading up some PA35, guessing the up/down position and aiming for that ..... but neither of these methods would account for all the turret/lens holder adjustments.

How could I be sure the centre of the laser is aiming 'squarely' at whatever centre marker I choose to use? i.e. How can you be sure the lens holder is perfectly perpendicular to the film plane? I may be able to place the laser spot on the centre marker, but it could originate from anywhere.... and with the short range involved, I doubt I would be able to see any elliptical spread in one direction..... so, the mind boggles. Perhaps I am a complete dumbass, and there is a dead simple way to do this ..... if so, don't flame me guys. [Big Grin]

Posted by Mark Gulbrandsen (Member # 72) on 02-04-2003, 03:23 AM:

Just make sure the stops for the aperature plate are set to allow you to be in the center of the range. This should give you enough adjustment range to allow you to bring things in properly after geting back to ground zero. You would need to have a precision drilled aperature plate made by a machinist for this purpose. Not too hard or time consuming to manage. The hole just has to be dead center...this plate would be considered a precision gauge after its made....so treat it as so. I've yet to see a factory aperature plate thats dead center....
I made a pinhole apreature for Simplex's that works pretty well. After re-alignment, its usually a piece of cake to get things on the screen looking good. Don't however be too upset if you find the lamphouse to projector alignment is not even close when you use the Align-O-Tron. Also, keep in miind that its not perfect either, the spot is not round!. It gets you very close, but is not using the actual focal point of the reflector as the ultimate refrence point...meaning that you may still have to fudge a bit. If you have access to a USL PSA light meter you'll see what I mean!!
Mark

Posted by Matt Close (Member # 996) on 02-04-2003, 03:41 AM:

The aperture plate has adjustable stops too ..... so the plate itself could be drilled as accurately as you like, and still be mis-placed by the holder it sits in .......

BUT, the main point I am interested in is how to be sure your lens is really perpendicular to the film plane

Posted by Manny Knowles (Member # 1171) on 02-04-2003, 12:26 PM:

I have wondered about this also. Would the little diamond in the middle of the PA-35/RP-40 test film be of any use here? How accurately placed are those crosshairs?

(Right now I use a pinhole aperture plate for my Kelmar traps.)

Posted by John Pytlak (Member # 331) on 02-04-2003, 01:24 PM:

SMPTE RP40 specifies the placement of the center target diamond in section 4.10 - Location on film and tolerances: "The center of the test image shall be within +/- 0.001 in (0.03mm) of the center of the projectable image area specified in ANSI/SMPTE 195."

Of course, framing adjustment of the projector affects the vertical centering.

Posted by Matt Close (Member # 996) on 02-04-2003, 06:27 PM:

Well ... I am thinking the PA35 is going to be more the go for me ..... but I will mark a blank aperture plate with a dead centre vertical 'line' using a metal scribe, so I can adjust framing to that.

In those surreal, blurry moments between being asleep and awake this morning ..... you know what I'm talking about [Wink]

...... when I seem to have some of me best ideas, I had this one. I haven't played with lasers very much, but what if I polished up a blank aperture plate? .. Would it be reflective enough to reflect the laser back so I could see where it was aimed.....then adjust the turret's locked position to send the laser back on itself? If that were possible to do, I should then have the turret parallel with the film plane, and be able to adjust the lens mount, and turret stop positions to line up with the PA35, and the scribe line in the aperture plate..... I hope [Big Grin]

As an afterthought, Manny ... can you try your Align-O-Tron with a bit of PA35 laced up, and maybe a blank plate if you have one, and tell me if it 'does' reflect a visible spot back to the turret..... thanks.

Posted by Greg Mueller (Member # 17) on 02-04-2003, 06:41 PM:

The Align-O-Tron puts out pretty good light, and really all you need is a portion of that light to be reflected back to try your idea out. A bit of plastic or maybe even the non-emulsion side of the film might give you enough of a reflective surface. All you need to see is a very slight reflection. Same with aiming the reflector. I think it was Brad that said he'd used a CD jewel case. Mark G used a piece of broken port glass. Keep it simple (that's my motto).

Posted by John Walsh (Member # 168) on 02-04-2003, 09:55 PM:

I have always wonder if there was some kind of order one would follow to insure everything is lined up, like; intermittent sprocket to trap; then trap to aperture; then aperture to lens holder; etc.

I'm guessing, but I would think that you would use the Align-A-Tron to get close. Then, if you wanted to be very critical, you could run the 35PA and look for some kind of chromatic abberations (different colored squares right next to the black squares.) I'm guessing you should be able to adjust the reflector until the colored squares go away - they would merge into the black squares.

Of course, with the corse-threaded screws and nuts used, it sometimes tought to get things exactly where you want them. Although I realise the reflectors manufacturers don't want to put in an expensive XYZ adjusting carriage for a 'one-time-only' adjustment.

Posted by Manny Knowles (Member # 1171) on 02-07-2003, 09:46 AM:

To ensure vertical centering of the 35-PA test film: Project the test film through the scope lens without an aperture plate and use the measurements as a guide. This assumes that your screen is the right size and shape to match your scope lens. If your screen is too small or if it has the wrong aspect ratio (or both) then you may not be able to do this because the numbers will trail right off the screen and you will have no way of knowing if the test film is vertically centered.