:help: Need some lens design help.

[Poita]

I'm hoping an optics guru/nutter (I won't judge) can help me out with a project.

I want to capture some 16mm movie film to a Sony ICX285 2/3" progressive scan CCD.
I have built an LED lighting setup to replace the old hot bulb in the projector, but am not sure of the best way to get the image onto the CCD.

Can anyone help with lens suggestions to achieve this? Any help much appreciated, and I can supply a copy of the movie in question if it all works :^)


The frame size of the 16mm film is here:
http://en.wikipedia.org/wiki/File:16mm_and_super16.png
(Not Super16)

Thanks

-Peter

[Barrykgerdes]

A lot will depend on the quality you require. The LED light source should be mild enough for direct scanning your biggest trouble will be the mechanical coupling arrangement of the projector to the camera and what the focal range is of the camera.

The best way is a commercial projection box but I haven't seen one for a long time. or maybe you can locate an old TV film scanner and replace the vidicon with your Sony camera. This is probably the way I would try.

I used to convert my old 8mm film to tape ( digital) by just shining it on the screen and photograph it with the movie camera. I also had some done professionally and the difference in quality was hardly noticeable due mainly to the quality of 8mm movie film.

Barry

[mikerr]

Peter, it might be worthwhile contacting your local Television station.
They used to, and may still have, Telecine machines for playing Film Movies and transmitting them at the same time.
A projector played the film and a Vidicon camera looked at the projector lens. This system was still being used when CCD cameras took over from Tube cameras in the studios.

Michael.

Looks like Barry beat me to it. :)

[Poita]

I can't use a commercial telecine facility unfortunately due to the length (it would cost about $8,000 to transfer). The commercial units actually are pretty poor, except for the newer film scanners, which are out of my price range.

I have a solution already using the projector lens and a CCTV lens on the camera, it works fine, but those lenses are pretty sad optically, I'd rather get some good glass in the chain, but I have no idea about the most efficient optics layout to use.

[Poita]

Thanks Barry, the setup I already have working is far better than the last commercial transfer I had done. I'd just like to improve the optical path.

The light source I have built is computer controlled and allows me to get the exact light balance I require, that part i all working. (I can even run the film without a shutter and pulse the LEDs 24, 25 or 30 times per second to freeze each frame, it works a treat).

It is for a film restoration project, so I want to get the images in at least 12bit to capture the dynamic range of the film.

Alignment isn't an issue, I can fabricate the parts to get very fine alignment, it is just the arrangement of glass that is outside my expertise.

[Barrykgerdes]

Hi Peter

I would expect the camera to have a reasonable lens but the quality of most of the 16mm home projector lenses leave a bit to be desired. I think they are mainlly designed to handle the heat of the projection lamp. Why not experiment with a 26 mm or 32mm Possl telescope eyepiece on the projector.

Barry

[Barrykgerdes]

As a matter of interest. The commercial transfer of my 8mm movie was discovered when I bought a DVD and when I played it, it had sections from my film that I had given to a friend.

Barry

[Poita]

The camera has no lens, it is like an astro camera, just the CCD window for me to project the image onto.

So basically I want to project a flat image from the projector directly onto the CCD window, obviously at the approximate size of the CCD.

I'll give some eyepieces a go.

[Barrykgerdes]

I think a Telescope eyepiece of the dimensions I suggested might just do the job. Should not be too difficult to implement for a trial run.

The focal plane of the possl will be inside the base sleeve but you can remove that to get closer to the film plane.

Barry

[Poita]

I've got a 25mm plossl somewhere...
Any reason for the Plossl design and not something else?

[Barrykgerdes]

No other than they are better for telescope work than some of the cheaper type and you will probably have one on hand to try out.

Barry

[Poita]

Thanks, I have a bunch of various eyepieces, I'll give them all a go.

Can anyone draw me a picture of what the ideal lens elements and order would be for me to achieve what I am trying to do?
Oddly the film frame is almost the same size as the sensor frame, I almost just want the light to come collimated through the film and land on the sensor.