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Thread: Bolex 16 to 100 mm C mount lens

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    Bolex 16 to 100 mm C mount lens

    Hello,

    I have a Bolex 16 to 100mm zoom lens that came from a 16mm Bolex movie camera.

    This is not my lens but mine is just like this:
    http://www.ebay.com/itm/KERN-VARIO-S...ht_2136wt_1316

    I also have a Panasonic GH2 and a C mount to Micro 4/3 lens adapter.

    When I put the zoom lens on the GH2 I get a lot of vignetting and I hit infinity focus way before the lens focus ring reach the infinity mark.

    So I have two question:
    1) In order for me to get the infinity mark on the focus ring to more or less line up with the actual infinity focus do I shim the lens farther away from the camera or shave the adapter and get the lens closer to the sensor?

    2) In order to get a larger image circle to project on the sensor, do I shim the adapter farther away from the sensor or shave the adapter and get the lens closer to the sensor.

    All this is assuming I can do some machining which I do.

    Thanks in advance.

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    Re: Bolex 16 to 100 mm C mount lens

    Quote Originally Posted by HansenTsang View Post


    1) In order for me to get the infinity mark on the focus ring to more or less line up with the actual infinity focus do I shim the lens farther away from the camera or shave the adapter and get the lens closer to the sensor?
    Add a spacer between the adapter and the lens to move it away from the sensor.

    No. 2 can not be achieved by adding a spacer or trimming the adapter. Nothing mechanical can be done to increase the image circle.

    Unless you have a sentimental attachment or an unique purpose in mind, eBay it.

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    Re: Bolex 16 to 100 mm C mount lens

    Interesting isn't it that zoom lenses made for 16mm (same size as a 4/3rds sensor) will vignette at some focal length? I was hoping that surplus CCTV lenses made for larger than 1" (CCTV sensor measurement) sensors would start appearing, but it seems that CCTV cameras with larger sensors are using adapted regular Nikon 35mm lenses instead of dedicated larger image circle CCTV lenses.

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    Re: Bolex 16 to 100 mm C mount lens

    Quote Originally Posted by Vivek View Post
    Add a spacer between the adapter and the lens to move it away from the sensor.

    No. 2 can not be achieved by adding a spacer or trimming the adapter. Nothing mechanical can be done to increase the image circle.

    Unless you have a sentimental attachment or an unique purpose in mind, eBay it.
    Thanks. I know you have tested a lot of C mount lenses. I have no sentimental attachment to the lens. I have no clue if it is worth anything on eBay. I do like the smoothness of the operation and would love to get it working with the GH2 as a video lens. The zoom and focus is just so silky smooth. I have yet to find a good video zoom lens for my GH2 yet.

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    Re: Bolex 16 to 100 mm C mount lens

    Quote Originally Posted by RichA View Post
    Interesting isn't it that zoom lenses made for 16mm (same size as a 4/3rds sensor) will vignette at some focal length? I was hoping that surplus CCTV lenses made for larger than 1" (CCTV sensor measurement) sensors would start appearing, but it seems that CCTV cameras with larger sensors are using adapted regular Nikon 35mm lenses instead of dedicated larger image circle CCTV lenses.
    I thought the 4/3 sensor is larger than the 16 mm film size.

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    Senior Member RichA's Avatar
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    Re: Bolex 16 to 100 mm C mount lens

    Quote Originally Posted by HansenTsang View Post
    I thought the 4/3 sensor is larger than the 16 mm film size.
    You are correct. 10.26mm x 7.49mm for 16mm film frame size. 4/3rds is 17mm x 13mm or so. Explains the vignetting. I was under the mistaken impression that 16mm was exactly 1/2 the width and height of 35mm film, which it is not. I think I got this impression from the name and the fact the prime lenses I've used made for 16mm film haven't vignetted on m4/3rds gear.

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    Re: Bolex 16 to 100 mm C mount lens

    Quote Originally Posted by RichA View Post
    I think I got this impression from the name and the fact the prime lenses I've used made for 16mm film haven't vignetted on m4/3rds gear.
    I think some prime lenses for the 16 mm may have a much larger images circle so they work well with the m4/3rds. I was hoping this zoom was in the category. Unfortunately not.

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    Re: Bolex 16 to 100 mm C mount lens

    To answer your original question, the lens needs to be farther away from the sensor in order to have infinity match the focus scale's infinity position.

    However, it's not that simple. This is a Bolex RX (reflex) lens, so it's designed to have a prism between the lens and the film. This prism is, in effect, an extra lens element, and is an integral part of the optical design. The lens will never be 100% sharp without it.

    As you've discovered, 16mm lenses don't cover 4/3 sensors, so it's a moot point. Coverage is much better on the Nikon 1 and Pentax Q, so it would be interersting to make an RX adapter that includes the prism, or a block of glass with the same optical properties.

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    Re: Bolex 16 to 100 mm C mount lens

    Quote Originally Posted by HansenTsang View Post
    I think some prime lenses for the 16 mm may have a much larger images circle so they work well with the m4/3rds. I was hoping this zoom was in the category. Unfortunately not.
    A guy I know has a similar lens, f2.0, it's massive, at least 4" wide and 10" long and heavy. It just covers m4/3rds.

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    Re: Bolex 16 to 100 mm C mount lens

    Is that the 18-180 Ange ? RichA ?

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    Re: Bolex 16 to 100 mm C mount lens

    Quote Originally Posted by Bernard View Post
    To answer your original question, the lens needs to be farther away from the sensor in order to have infinity match the focus scale's infinity position.

    However, it's not that simple. This is a Bolex RX (reflex) lens, so it's designed to have a prism between the lens and the film. This prism is, in effect, an extra lens element, and is an integral part of the optical design. The lens will never be 100% sharp without it.

    As you've discovered, 16mm lenses don't cover 4/3 sensors, so it's a moot point. Coverage is much better on the Nikon 1 and Pentax Q, so it would be interersting to make an RX adapter that includes the prism, or a block of glass with the same optical properties.
    Thank you, yes I found out it is very difficult to focus on my GH2. I have used two C mount adapter and tried different distances to sensor and no luck. It will only focus at one specific point and if I zoom it the focus will go out. That pretty much makes the lens useless for me. I think I will just sell it on eBay and look for something else for the GH2.

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