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**BigMackCam** · 09-08-2015, 09:35 AM

Just before heading out the door for my late summer vacation (at the airport now!), the postman delivered a low cost 25mm fine lens I ordered, which came with a C-P/Q adaptor (lens seems like fun, very sharp in the centre but pretty poor out towards the edges - portraits, here I come

). Also with the adaptor came a second adaptor which screws into the C-mount and presents a wider thread. Can anyone tell me what this is for? Assuming it's for another type of lens, is infinity focus likely to be affected?

Professor Batty · 09-08-2015, 09:52 AM

Measurements or photos please!

**UncleVanya** · 09-08-2015, 10:58 AM

Originally posted by Professor Batty

Measurements or photos please!

Ditto.

abwx · 09-09-2015, 05:12 PM

Is this just a little larger than C-mount? Diameter over threads maybe ~29mm vs ~25mm? If so, it could be a Bell & Howell Tri-Lens mount, which provided three lenses for 16mm cine in a rotating turret. The longer flange distance allowed for the turret, and makes an adapter for C-mount feasible, while providing infinity focussing.

**BigMackCam** · 09-09-2015, 10:53 PM

Thanks for the responses. I'm on holiday at the moment so don't have access to the adapter, but further online reading suggests the additional piece might be a macro adapto- ie. same diameter thread but bringing the lens forward like an extension tube.

Professor Batty · 09-10-2015, 07:11 AM

That's probably a CS adapter:

http://www.ikegami.com/cb/products/pdf/tech/lensmount.pdf

Professor Batty · 09-10-2015, 08:43 PM

"…a low cost 25mm fine lens I ordered…" It may well be a cs lens with an adapter.

We need some info.

**BigMackCam** · 09-10-2015, 11:07 PM

No, it's a c mount Fujian lens with a C-P/Q adapter, for sure. The lens fits that adapter and focuses to infinity, so that's all good. It's only this addition screw in ring that puzzled me, but as I say, researching online suggests it may be a macro extension ring. I'll check it when I'm back from my trip.

**pacerr** · 09-11-2015, 05:07 PM

A 'macro extension ring' could just as easily be an additional mount adapter to accommodate 'normal' focus for a second lens with a longer RD and with a compatible diameter thread. I've used step-up/down rings that way with so-so results.

09-08-2015, 09:35 AM	#1
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,706	C-P/Q adapter - and an additional screw-in adaptor?? Just before heading out the door for my late summer vacation (at the airport now!), the postman delivered a low cost 25mm fine lens I ordered, which came with a C-P/Q adaptor (lens seems like fun, very sharp in the centre but pretty poor out towards the edges - portraits, here I come ). Also with the adaptor came a second adaptor which screws into the C-mount and presents a wider thread. Can anyone tell me what this is for? Assuming it's for another type of lens, is infinity focus likely to be affected?

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09-08-2015, 09:52 AM	#2
Professor Batty Senior Member Join Date: Aug 2012 Posts: 118	Measurements or photos please!

09-08-2015, 10:58 AM	#3
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,472	Originally posted by Professor Batty Measurements or photos please! Ditto.

09-09-2015, 05:12 PM	#4
abwx New Member Join Date: May 2015 Posts: 3	Is this just a little larger than C-mount? Diameter over threads maybe ~29mm vs ~25mm? If so, it could be a Bell & Howell Tri-Lens mount, which provided three lenses for 16mm cine in a rotating turret. The longer flange distance allowed for the turret, and makes an adapter for C-mount feasible, while providing infinity focussing.

09-09-2015, 10:53 PM	#5
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,706 Original Poster	Thanks for the responses. I'm on holiday at the moment so don't have access to the adapter, but further online reading suggests the additional piece might be a macro adapto- ie. same diameter thread but bringing the lens forward like an extension tube.

09-10-2015, 07:11 AM	#6
Professor Batty Senior Member Join Date: Aug 2012 Posts: 118	That's probably a CS adapter: http://www.ikegami.com/cb/products/pdf/tech/lensmount.pdf

09-10-2015, 08:43 PM	#7
Professor Batty Senior Member Join Date: Aug 2012 Posts: 118	"…a low cost 25mm fine lens I ordered…" It may well be a cs lens with an adapter. We need some info.

09-10-2015, 11:07 PM	#8
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,706 Original Poster	No, it's a c mount Fujian lens with a C-P/Q adapter, for sure. The lens fits that adapter and focuses to infinity, so that's all good. It's only this addition screw in ring that puzzled me, but as I say, researching online suggests it may be a macro extension ring. I'll check it when I'm back from my trip.

09-11-2015, 05:07 PM	#9
pacerr Loyal Site Supporter Join Date: Jan 2008 Location: Paris, TN Photos: Gallery \| Albums Posts: 3,350	A 'macro extension ring' could just as easily be an additional mount adapter to accommodate 'normal' focus for a second lens with a longer RD and with a compatible diameter thread. I've used step-up/down rings that way with so-so results.

C-P/Q adapter - and an additional screw-in adaptor??

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