If you don't know about the Align-O-Tron. It is a laser-equipped device for doing optomechanical alignments.

Visit the website for a detailed description:
http://www.muellersatomics.com/alignotron.htm

I got my kit some time ago and I finally made a special trip to the cinemas just to try it out. I think it's great but it took me a few tries to get the hang of it.

I always ended up having to readjust the height of the anode for some reason...

...and then it hit me...

...How do I know that the lenses are centred to the aperture?

Seems to me that what I need is a special "dummy" aperture plate with a hole drilled dead-centre of the picture area.

I took a new aperture plate and got the local aluminum shop to cut a matching piece (with no apertures cut into it) and now what I need is an idea of how to locate the absolute centre of the picture area.

I inserted it into the film trap and scribed the shape of the opening onto the blank plate.

Next I made corner-to-corner crosshairs to locate dead-centre.

However...that exposes the soundtrack too...so centre of the picture area would be slightly to one side of that. A piece of RP-40 revealed how far off-centre to drill.

I just did this today, so I haven't tried this as part of an actual alignment yet.

I'll post a pic when my camera is working again.

I mean, I get the idea...It's what I've been making by hand, right?

But is this something I can purchase ready-made from Kelmar instead of reinventing the wheel?

Note to Greg: Let us know if/when you make a model that points from the reflector out to the lens...hint hint.

 |  IP: Logged

Pinhole apeture plates are a standard plate that can be ordered from your cinema supply house. It's for the poor tech who's plate geometry is so far off any of the standard size plates that he has to file down from a hole in the center of the plate, out to exactly where he needs it.