Replacing pellicle mirrors/beamsplitters on one-shot tricolor camera

iandvaag · Jul 26, 2019

Hi all,

I recently purchased a Curtis color scout 4x5 one-shot tri-color camera. The pellicle mirrors were damaged during shipping. Has anyone had experience replacing these? It looks like you might be able to get replacement pellicles from National Photocolor, but I haven't inquired yet.

The manual says:
"The installation of new mirrors and the re-registration and test of the camera must be done at the factory where the special optical jigs and test equipment are available."

Elsewhere it reads:
"This membrane is stretched upon a glass frame which has been optically worked to create a flatness and parallellism which is measured in millionths of an inch."

Is this a task best left to an expert? If so, is there anybody who would do this?

Thanks,
Ian

Europan · Jul 26, 2019

Your main problem is that pellicles need to be coated on one side. I have a number of membrane reflex finder movie cameras that I’d like to bring back to use but the costs of dereflexing glasses (that I have) cracks my purse.

Dan Fromm · Jul 26, 2019

If you can read French or are comfortable with machine translations, ask Henri Gaud for advice. His blog: http://trichromie.free.fr/trichromie/ He posts on galerie-photo.info as Nestor Burma, can be reached through there too.

AgX · Jul 26, 2019

Ian, that is an interesting source, as the sources I knew so far only offered off-the-shelf and those pellicles were too small.

These pellicles are made for scientific standards, likely more strict than your project needs. Problem would be to install those frames in your camera, you likely will have to make new holders for them.

AgX · Jul 26, 2019

Europan said:
Your main problem is that pellicles need to be coated on one side.

Those scientific pellicles are coated.

If the reflection ratio needed by the camera design is offered, then there should be no problem in this respect.

iandvaag · Jul 27, 2019

Dan Fromm said:
If you can read French or are comfortable with machine translations, ask Henri Gaud for advice. His blog: http://trichromie.free.fr/trichromie/ He posts on galerie-photo.info as Nestor Burma, can be reached through there too.

Thanks so much, Dan!

AgX said:
These pellicles are made for scientific standards, likely more strict than your project needs. Problem would be to install those frames in your camera, you likely will have to make new holders for them.

AgX said:
If the reflection ratio needed by the camera design is offered, then there should be no problem in this respect.

Yes, I imagine those pellicles would be suitable, my main concern is that I don't think I'm capable of installing them. They are very delicate, and I've been having a hard time simply trying to carefully remove the old frames from the camera! The manual specifies that the first mirror is 32% reflective and the second mirror is 35% reflective, so I imagine it wouldn't be to difficult to adjust metal deposition to achieve those reflectivities.

Thanks!

thuggins · Jul 30, 2019

I have been thinking a lot about a color separation camera, Congrats on finding one. Too bad about the mirrors

Have you thought about updating the camera using dichroic mirrors? I built a beam splitter using 45 degree green and red dichroics to direct the three primary colors to separate targets.

iandvaag · Jul 30, 2019

Dichroic mirrors would be great, since you could probably get better light throughput to each sheet. Do you know of any source of large dichroic mirrors? They need to be 4x5, and they probably need to be coated on a pellicle to avoid back reflections. I'm only aware of small dichroic cube beamsplitters used in digital projection systems and 3 CCD cameras. Surplus shed had some larger 2" ones in stock last I checked, but I imagine it would be a lot of work to make a functional camera out of one.

I have a feeling this project is going to be very involved and probably expensive

AgX · Jul 30, 2019

iandvaag said:
They need to be 4x5, and they probably need to be coated on a pellicle to avoid back reflections.

They definitely would need to be a pellicle.

Replacing pellicle mirrors/beamsplitters on one-shot tricolor camera

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