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View Full Version : Film SLR as webcam - pros and cons?



omaroo
June 19th, 2007, 10:15 AM
Hi all

After musing over a photo of the Pentax film body with the webcam PCB mounted inside shown below, I've been thinking of doing the same to my Nikon N50 - which I will probably never use again as a day to day unit as I still have two other film bodies that are far more valuable to me (Nikon F and Nikon EL) and now the D40 DSLR. I paid $50 for it on eBay so it's absolutely perfect for the job. It still mounts all my Nikon lenses - which is why I'm interested.

After getting involved in my peltier-cooled webcam project I think I'd also like to try doing the film-CCD conversion on the N50 as a bit of fun. It looks relatively easy to mount the webcam PCB with the CCD still mounted where it should be right on the film plane from the back. If I remove the film pressure 'sled' then it would leave plenty of room for the board.

Now - what would I end up with? Do the camera's electronics become irrelevant just because I'm exposing to CCD rather than film? I guess so as the webcam isn't designed to be exposed for a brief time, but rather outputs a constant video stream. What if I were to perform a long exposure mod on the webcam - would it work the way intended then as the shot would trigger the mirror to flip and the shutter to open - exposing the CCD for a brief time?

The N50 doesn't have mirror lock-up, but it does have a bulb setting - so normal video streaming mode would work if this were set. I've just tried it and the mirror stays up with the shutter open until I re-press the shutter button.

The bulb feature works to keep the mirror up and the shutter open - and once I replace the battery with an externally-wired 6v DC source power shouldn't be a problem. At this stage I don't plan to use the timed shutter - but to just keep it open so that the webcam can operate as a normal streaming video device to capture moon or planets - only with a nice Nikon lens up front.

I don't plan to actually remove anything as such - it's purely a mechanical job to mount the CCD and board on the film plane with very minor modification. There's even four beautifully-placed screws on the backplane that will aid in mounting the board. I'd have to remove the little speaker from the webcam's PCB - but that's a no brainer as it serves no purpose anyway.

The question I have is what reaching focus will be like - as the focal plane is in the same place - the only difference being the size of the sensor in comparison to the size of a 35mm frame. I hope that I can center the CCD to picj up a 640x480 pixel "window" within the 35mm frame.

Any ideas anyone?

Cheers
Chris

The Pentax (from "Digital Astrophotography: The State of the Art" by David Ratledge (Ed) from Patrick Moore's Practical Astronomy Series, published by Springer)

http://www.omaroo.net/albums/album34/Pentax_ToUcam.jpg

The Nikon N50 - nice and cheap on eBay!

http://www.omaroo.net/albums/album34/NikonF50aAdorma.jpg

http://www.omaroo.net/albums/album34/DSC_0615.sized.jpg

http://www.omaroo.net/albums/album34/DSC_0619.sized.jpg

http://www.omaroo.net/albums/album34/DSC_0621.sized.jpg

Radar
June 19th, 2007, 05:41 PM
Awesome project Chris.

I imagine focusing would be quite simple. Buy a ronchi screen or knife edge focuser for that camera, then use a depth gauge to work out the tiny difference that the ccd creates, then calibrate your focusing device. This is what I would do. Otherwise you could always do some focusing in real time by watching the computer screen.

What webcam chip are you mounting inside it?

Cheers

Ray

AstroTasmania
June 21st, 2007, 06:37 AM
Hi Omaroo,

Would it not be easier to just buy a Mogg web/35mm lens adaptor to use your Pentax lenses with your webcam? http://moggadapters.com/astro/adapter.asp

Just a thought, I have several (different) of them so I can use any of my SLR lenses.

Clear skies...

omaroo
June 21st, 2007, 07:20 AM
Hi Shevill - thanks for replying. I'm aware of the Mogg units but they don't quite give me what I'm looking for.

I actually want to produce a webcam that has a viewfinder. It wouldn't have to have a separate finder just to get it to point somewhere, and if I carefully adjusted the PCB's mount such that I could accurately line up the face of the CCD right on the old film plane then focussing through the viewfinder would be an advantage too. The N50 has a very nice, unobtrusive clear matte viewfiner screen as standard so it would be good for what I want.

I also like the idea of experimenting with the webcam set to both normal and long exposure modes and trying the shutter at various speeds to see what happens.
Just fun I guess.