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New C-Mount Primes


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#1 Anthony Schilling

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Posted 26 March 2017 - 12:04 PM

I'm wondering if anyone can give me an idea on the quality of new consumerish C-mount primes like Computar, Kowa, Fujinon, or Ricoh? How do they compare to older primes like Angenieux, Wollensak, Kern, Switar? The BMPC people have been buying up a lot of the old ones, they want $300 and up for most of them now. The new ones sell between $100-$300.


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#2 Pavan Deep

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Posted 27 March 2017 - 03:30 AM

I can only share my experience, from what I know, most of the new c mount lenses you mention are designed for 1, 2/3, 1/2 and 1/3 inch digital sensors, I think they are made to different standards to cine lenses, but I don't know what these differences are. I don't think there have been many tests done with these lenses on film cameras. I have used the small Pentax lenses which are for 1 inch CCTV cameras on my 16mm cameras and have found them to be very fast and sharp.

 

Pav 


Edited by Pavan Deep, 27 March 2017 - 03:31 AM.

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#3 Anthony Schilling

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Posted 28 March 2017 - 11:23 AM

Thanks Pav, I'm eying some lenses for the new Kodak S8, which comes with a 6mm Ricoh. I'm looking at 12mm to start and maybe some longer lengths later. Anticipating those lenses I mentioned will be much sharper than most S8 fixed zooms.

Edited by Anthony Schilling, 28 March 2017 - 11:25 AM.

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#4 Robert Hart

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Posted 13 April 2017 - 04:07 PM

There are some really low-cost C-Mount lenses out of China which wear the brand name "Fujian" in focal lengths 25mm,35mm and 50mm.

The image circles on these are suitable for Super16mm. My examples which I bought in for a home-build scanner yield comparable sharpness numbers on the SI2K camera to the Optar Ilumina and CP Ultra T* lenses. The machining work is good but the actual focus movement is rather "basic" relaying upon a grubscrew registering in a single helicoid channel to slide the entire group of optics forwards and rearwards for focus adjustment.

However, the fit is snug and with the dampening grease used, there is no observable "hop" or image shift. That might change as they age and the lube thins or dries out. The focus ring is retained from moving off the front of the lens barrel by a screw-in front which may be loose or barely hand-tight when received.

There is no secondary grubscrew retention of this threaded ring. When loosening or tightening this front threaded ring, or removing the lens from a baulky C-mount, EXTREME care needs to be taken that no rotating force is applied to the aperture ring or it may ride over the internal actuator or damage the iris blades. There is very little lens body to grab hold of.

Your lens focus ring may be found to be immovable when you receive the lens. This will likely be due to the lube having dried near the gaps and hardened. Unscrewing the front a few turns and pulling the focus ring forward will draw the internal lens block forward, crack the lube and it will move freely and smoothly thereafter. Take care not to use too much force or the grub screw may be broken off. 

If the lens  block is really frozen in dried grease, it is better to screw the focus ring off entirely and then attempt to push the lens block forward from the rear taking care not to damage  or soil the rear optical element by protecting it with cloth or tissue.



http://www.ebay.com/...~UAAOSw-4BXYOzQ

If you buy on eBay from the chinese vendors be careful to additionally state in your payment message that a specific focal length is required. When ordering a 50mm lens I received a 35mm lens in error. The costs involved do not justify sending one back.


Edited by Robert Hart, 13 April 2017 - 04:12 PM.

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