Strange 0.734 x 0.710 aperture plate opening size

[Adam Liberman]

I obtained a Century C with two aperture plates. One measures 0.825 x 0.598, so I know that it is for Academy 1.375:1. But the other measures about 0.734 x 0.710. It has the same optical center as the Academy plate. What format could this have been for? I could file out the width to make it an anamorphic 2.39 plate, which I need, but I'm curious what it was used for. I found it being used in another Century C. And if I do file it wider, how would I file that much off and keep the edges straight? Thanks.

[Ryan Gallagher]

FilmTech has plates if you prefer not to file those mystery ones. At that size I would guess a version of scope 2.35 or scope 2.0 was the intent?

Remember plates/lenses/screens are generally a set after filing. So I would assume those "found" ones are not perfect for you anyway, if you can turn it into a useful one due to it being smaller than needed, go for it.

I recently did some plates starting from blanks, I found wider files, perhaps angled until they match the width of the opening, useful for removing bulk material while trying to maintain the line.

But the general rule is just to go real slow removing a tiny bit at a time, have your masking preset on screen to your target opening, ideally using the film but a good SMPTE 35PA reference image can also work to set your masking. Then just file up to your masking with no film in the gate. If your masking is movable you can blow it out after and check how straight your lines ended up, but at that point it is often too late to do much touch up without putting more image on the masking.

Once you are into the precision range, a diamond nail file works pretty well too if you don't have one of the more intentional plate files.

[Ryan Gallagher]

Also if you haven't encountered a list yet, here are the plate openings from the OEM century JJ manual. Note I'm not sure if the plates themselves were equivalent to those in Century-C units.

[Adam Liberman]

Thanks Ryan for the explanation and suggestions! This will be for a home cinema with an 8 to 10 foot wide image, so I don't anticipate needing to file or being able to find exact size lenses. I will contact Film-Tech also about the plates -- didn't know that they sold them. Thanks!

[Ryan Gallagher]

Cheers. For home use I would think standard flat and scope and/or plates filed to the relevant SMPTE 35PA reference lines would suffice as a starting point. 1.33 and 1.66 are nice to have eventually. Undersized prints (which are pretty common) will just expose matte lines, but works fine for home use. If you don't have a ton of keystone or a weird size screen/lens combo... not much call to start from severely undersized plates and file custom ones.

[Ryan Gallagher]

And a word of caution. Apologies if you are aware. When testing without film in the gate, don't leave the lamp house dowser open for longer than a minute or so, to protect the lens elements from the extra heat, Same principal as when tuning the lamp xyz alignment and field.

[Adam Liberman]

I'm not sure what I will use as a lamp house. I do have access to obtaining an Orcon 1 kW self-contained xenon lamp house, but I'm concerned that it will be too bright for the screen size (although I was thinking that I could stop down the lens or insert a fixed aperture disc and get great corner sharpness). I was aware of the issue with running light through the lens with no film, but is that still an issue using a 1 kW or smaller lamp?

And then I'd need more space, and a heavy iron pedestal to support it. I was thinking of possibly designing an LED lamp house, or finding a 550 W xenon (I have a 500 W slide projector, but not sure how I would adapt that safely). I could also do incandescent, but then the color temperature would be wrong.