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C-mount adapters

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Vivek

Guest
Edlamps, I never said that they are cs mount lenses!

The problem (as I see it) is the mount not being able to fit inside a c-mount adapter due to physical limitations in the case of the lens on the left. It appears that the right lens' rear would protrude too much in to the cam.

I (and others) can verify them to be c-mount lenses if you would care to tell us what they are!
 
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edlamps

Guest
Thanks, Vivek. Why didn't I think of that!?

The left one is a Computar TV Lens 12.5mm f1.3
Just got this two days ago from Surplus Shed in the mighty USA
http://www.surplusshed.com/pages/item/l3943.html
and it definitely says 'C-Mount'!!

The right one is also Computar, an 8mm f1.3 which I got from eBay for pennies.

So, to achieve infinity focus do I not want them to protrude further into the camera body then? Isn't this what machining does? I'm doubly confused now. hmmm.
 

photoSmart42

New member
The Computar 12.5/1.3 is definitely C-mount - I have one along with the Cosmicar version. They do require some modification to the mount to make them fit the adapter, but it's honestly not that major. Just some grinding around the base by a few millimeters here and there. Different amounts of machining are required based on the adapter you have.
 
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edlamps

Guest
OK, thanks guys.

What is the best method for grinding (without damaging) the lenses?
 

photoSmart42

New member
What is the best method for grinding (without damaging) the lenses?
Take off the rear mount if you can, then machine it. The Cosmicar and the Computar lenses have 3 screws on the rear mount you can take out (make sure you don't lose them) to remove the mount. You can also use that to align the mount correctly to the m4/3 camera body so you can see the lens markings. Ideally you should do your machining on a lathe, but with some patience you can do it by hand.
 

edz

New member
The lens on the right has a rear element which protudes too far beyond the rear mount (the silver part of your lens) to make it usable on m4/3. I don't think you would be able to make it focus very far without the rear element blocking the camera's shutter mechanism.
 

kds315

Active member
Got the C5 adaptor from Hawk and noticed that the outside is that smooth (or lacks any grip) that it can hardly be taken off if mounted on my GH1. Similar experiences?
 
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photoSmart42

New member
Got the C5 adaptor from Hawk and noticed that the outside is that smooth (or lacks any grip) that it can hardly be taken off if mounted on my GH1. Similar experiences?
Same with my Kipon adapter. That's why they included the adapter removal tool with their adapter. I don't mind the lack of grip that much because it means they've shaved as much depth as possible in order to fit most lenses while maintaining some semblance of mechanical rigidity.
 
V

Vivek

Guest
Got the C5 adaptor from Hawk and noticed that the outside is that smooth (or lacks any grip) that it can hardly be taken off if mounted on my GH1. Similar experiences?
It looked a bit worrying when I received it. Especially since he shows two versions (eBay) and shipped the plain one to me.

I do not have problems with mounting/dismounting on my G1s (each cam has a slight tolerance variance but the C5 adapter still is manageable with all).

[I must admit that I have been tinkering around with adapters on the G1s ever since beginning and have one bad experience (none of the current adapters) with a Pana WV CCTV cam adapter that ripped a few lens contacts off. So, it is fair to say that I am fully aware of the fragility of the m4/3rds mount]
 
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edlamps

Guest
Ideally you should do your machining on a lathe, but with some patience you can do it by hand.
What if I don't know anyone with a metal-grade lathe? What's the best tool with which I can achieve the same result?
 

Jonas

Active member
What if I don't know anyone with a metal-grade lathe? What's the best tool with which I can achieve the same result?
I used a file, it took about 30 minutes of contemplating and filing at the kitchen table to make the Computar 12.5/1.3 fit the adapter. A vernier caliper came to use before grinding; measure the adapter and the rear end of the lens and then make a mark around the rear end so you know how far to grind it down.

The result won't be as nice to look at but it works just as well (and when the lens is mounted you can't see anything of the work anyway.

/Jonas
 

photoSmart42

New member
What if I don't know anyone with a metal-grade lathe? What's the best tool with which I can achieve the same result?
I used a Dremel. I don't have access to a lathe either for the moment. If I continue experimenting with camera mounts and accessories, I may consider getting a hobby lathe.
 

Y.B.Hudson III

New member
Computar 12.5mm, 1.3; 25mm, 1.3; 50mm, 1.3; 75mm,1.4 lenses all fit the "MS Optical m4/3 to C-mount adapter"* without any alteration...


* available @ Japan Exposures website
 
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edlamps

Guest
Computar 12.5mm, 1.3; 25mm, 1.3; 50mm, 1.3; 75mm,1.4 lenses all fit the "MS Optical m4/3 to C-mount adapter"* without any alteration...
That's interesting! But with every answer arises more questions... I had a look on the website & there's both 'S' & 'L' versions - should I assume you're talking about the 'S(mall)' version?

Also, it's quite expensive - is it worth spending that much on getting the Computar to work when ultimately I am saving up for my dream c-mount lens? (Or will this adapter be worth it for any future lens purchases too?)
 

RichA

New member
Two adapters, radically different prices

On the left, a c-mount adapter from a company called, Harper Logistics Ltd out of Hong Kong. On the right, an RJ Camera Adapter.
Cost of the RJ was $38.00 plus shipping.
Cost of the other one, $7.99 and no shipping.
Differences:
The RJ is thinner, narrower and fits slightly better. It also has only 1/2 the c-mount thread depth. The other adapter is more robust, but has a tad of circular play when attached.

 
V

Vivek

Guest
I believe the MS Optical thingy costs a few times that of RJ.
 
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edlamps

Guest
I believe the MS Optical thingy costs a few times that of RJ.
Indeed - £81.82 plus shipping from Japan, which works out at £3.15 (for untracked, uninsured airmail to Europe) to £11.26 (insured and trackable).
 

Y.B.Hudson III

New member
no sympathy for those who didn't join in the revolution of 1776...and now have to pay an exorbitant value added tax :) I have about 10± lenses with the computar mount... My first was a successful conversion, the second, was a failure. So I bought the MS Optical for USD $100±... If I amortize the cost over the 10 lenses and include labor saved and replacement costs for the mucked up mounts, the adapter more than paid for it self.

It was Later I discovered that the computar mount (with out conversion mutilation) could be used on the RJ adapter, by simply removing the helicoil stop screw. I still use the MS optical, because it is cute, and looks good in camera porn shots. :thumbup:
 

zcream

New member
Re: Two adapters, radically different prices

Hi Rich. Which seller gave you a m43 adapter for 7.99/- Cheapest I can find is 16/- on ebay. No one seems to have free shipping.

On the left, a c-mount adapter from a company called, Harper Logistics Ltd out of Hong Kong. On the right, an RJ Camera Adapter.
Cost of the RJ was $38.00 plus shipping.
Cost of the other one, $7.99 and no shipping.
Differences:
The RJ is thinner, narrower and fits slightly better. It also has only 1/2 the c-mount thread depth. The other adapter is more robust, but has a tad of circular play when attached.
 
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