1/2" Bayonet mount Sony DXC-327 35mm adapter question at DVinfo.net

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Old February 18th, 2006, 02:57 AM   #1
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1/2" Bayonet mount Sony DXC-327 35mm adapter question

i need to get a lens for my Sony DXC-357 1/2" 3ccd camera. it uses a sony bayonet mount. Now, the only thing i want to do with this camera anyway is to focus it onto a GG plane. What type of lens can i use to fill the bayonet mount? ive heard of relay lenses for the XL1 and stuff. but what are they, and how can i use something of this nature for my camera. kinda like how the PS technick Mini35 hooked up to the JVC-hd100u. i want something along that route. how can i make it work? thanks
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Old February 19th, 2006, 02:28 AM   #2
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Forrest.

Since I see no other answers here, her eis my two cents worth. Inore at will as I am no expert.

I did a bit of a study of a 2/3" (B4 mount) cam at one of our local broadcasters. There is quite a bit of space within and behind the mount ring on a Sony Betacam 2/3" ENG cam.

With 1/2" which I think may be a smaller B3 mount there may not be the same amount of space.

If your cam will operate without its lens in place, I suggest you investigate your nearest security company which deals with CCTV camera monitoring systems. Ask to see any "C" mount, not "CS" mount lenses they may have in the ball park of 25mm to 35mm focal length.

Before you go down there, make yourself a little test chart with a frame drawn on it of 24mm x 18mm or a grocery barcode of about the same size. If you are going for a larger image frame off the groundglass, the draw a larger frame or use a larger barcode or postage stamp.

Use a photo frame or anything to make the test chart stand upright in line with the centre axis of the camera lens when the camera and the stand are sitting on a common level surface.

At your security camera store, set up your camera and your test chart on the level surface w iththe test chart some 5 to 7 inches from the mount face of the cam, switch the cam on.

Set the c- mount lenses to infinity focus and aperture wide-open. Position them within the mount ring so that the flange face of the c mount is about 21mm back inside the camera housing within the B3 mount if it will fit.

Take care not to let it fall inside and scratch or damage the mask inside the cam. You might need to make a little shield out of clear thin plastic to insert beforehand as a protector.

The image you get in the camera will hint as whether you can make a relay lens to fit. Altertnatively, P+S Technik may have a relay lens which fits. I think I have seen reference here to Schneider-Kreuznach lenses. Those on old Bolexes were very compact.

Don't be too concerned if there is a vignette on an otherwise sharp image in which you can see frame edges which co-incide with your camera viewfinder edges. (Be careful not to use the TV safe-area marking as you reference but a wider frame which co-incides with the full CCD image.)

Most CCTV security lenses are for 1/3" cameras. C-Mount lenses are available which cover 1/3", 1/2", 2/3" and 1".

If you can get an image, this will indicate whether you can progress furthur to getting a special adaptor made.

As I say above, don't take too much notice of my comments as I am no expert.
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Old February 20th, 2006, 11:36 PM   #3
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thank you so much Bob! sadly, i checked my camera, and i have like no clearance for anything to go past the mount inside the camera. it would hit the glass right away. i think im giving up on this project. too much work with adapters, power supply...$$$... i will probaly sell the DXC-327. and go with a new project, like these elphel cameras.

http://www2.elphel.com/index.html

it could give me high quality results with little bank.
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Old February 21st, 2006, 01:00 AM   #4
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i may be interested in buying the dcx from you.

plz send me an email to infurno@gmail.com
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Old February 21st, 2006, 07:26 AM   #5
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Forrest.

If the glass is very close to the mount ring, this may not be a bad thing.

I would still be inclined to do the C-mount lens experiment. There's another test you can do.

If the existing camera lens can be zoomed to an approximate 25mm - 35mm and hold that setting after being disconnected or be manually zoomed and focussed off-camera and the camera still produce an image with the lens disconnected but still on the centre axis futhur forward, try the same experiment with your camcorder's lens to get a ballpark idea of things.

If you can get a full frame on a 24mm x 18mm sized target and a sharp focus with the lens set at or close to infinity, with the lens moved forward about 11mm and the target sitting about 5" to 8" away, your camera might still be a candidate for a flip style device. If the lens has to be more than 11mm forward from the mount to get a sharp and correctly framed image, then all the better. This may still leave you the option of a c-mount lens.

The need to use a C-mount lens if possible I think may be driven only by the much greater choices of fixed focal lengths available as prime lenses.

If you get get the sharp and correctly framed image, then the next step is to test for the in-air flange to focal plane of your own camera's lens.

That is as simple as getting a piece of wax paper or a shopping bag for a groundglass screen and holding the lens away from it until there is a sharp image on the groundglass, then measuring from the rear face of the lens mount on the lens itself to the groundglass surface.

The c-mount lens flange to focal plane is 17.5mm. Some parts of the lens sit furthur behind towards the camera. Parts of your videocamera lens may well sit furthur behind the flange face than a c-mount lens. If the camera's own lens has to be moved forward 11mm or more to get the correct frame and focus of the 24mm x 18mm target, then the flange to focal plane of the c-mount lens in the close-up mode will be the 17.5mm plus whatever the added distance furthur forward is for you camera's own lens for the same mm setting indicated on the zoom ring for a matching fixed c-mount lens.

This remains very wild guesswork as the behaviour of a zoom lens alters radically when moved off its normal position. zoom and focus also interact.
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Old March 4th, 2006, 04:51 PM   #6
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Bob thank you very much for all of your help. im getting ahold of a back for the camera hopefully pretty soon. and when i do, im going to try your idea with some c-mount lenses to see about making a relay lens for my adapter. thanks!
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