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11-06-2012, 04:36 PM   #1
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So naturally, I bought some crappy lenses.

I have my Q now. But before I even had it, I ordered some C mount lenses.



The lens on the left is a 25/1.4, available from a variety of chinese sellers. It's very cheaply built.

The lens on the right is a real beauty though. A little big for the Q, but with a great precision feel to the adjustments. Plus it's 5.7-34.2mm f/1.0, so the specs are pretty nice too. The crappy part is that it's CS mount, and for some reason I can't guess at no one makes an adapter. I've had a look though it by holding it up to the camera, coverage is close to good enough, certainly good enough for 1:1 format, depending on zoom it might be good enough for 4:3. Resolution seems semi-decent even at f/1.0, though this is very hard to judge without an adapter.

If I'm lucky I'll manage to modify one of my adapters for it, once they arrive.

11-06-2012, 05:04 PM   #2
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QuoteOriginally posted by drougge Quote
...for some reason I can't guess at no one makes an adapter.
Are you sure??? I've run across adapters like that all the time???

This one right?.... Focus Infinity 16mm C Mount Movie Lens to Pentax Q Camera Adapter Free Shipping | eBay
11-06-2012, 05:10 PM   #3
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QuoteOriginally posted by MysteryOnion Quote
Are you sure??? I've run across adapters like that all the time???
Pretty sure. C mount adapters (like the one you linked to) are easy to find. CS mount adapters, not so much. A CS mount adapter would be about 3mm thick, so it's easy to tell from the image that it's not a mis-described CS adapter.
11-06-2012, 05:26 PM   #4
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I have bought that exact item from that seller, it is certainly a C mount adapter. It is two piece, you *might* be able to get the center section milled down by 5mm which would turn it into a CS mount. I haven't measured if there is more than 5mm of thread available to mill down though.

The other possibility is to buy a D mount adapter and have it drilled/tapped for a 1″×32tpi thread. You may need to *slightly* shim the CS lens on this modified mount though due to slight flange differences between D and CS mount.

Shawn

11-06-2012, 05:26 PM   #5
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http://www.ebay.com/itm/10-x-5mm-metal-CCTV-Camera-C-CS-mount-Lens-Adapter-R...item3efff85e3e

Sorry about that... read that backwards...
How about a CS to C mount adapter? They seem plentiful too? Would that change the focus distance?
11-06-2012, 05:29 PM - 1 Like   #6
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"How about a CS to C mount adapter? They seem plentiful too? Would that change the focus distance?"

No such thing. What there are are adapters to mount C mount lenses (17.56mm flange distance) on a camera designed for a CS mount (12.56mm flange distance). In that case it is just a 5mm spacer ring, you can use the same ring as a macro extension ring for C mount lenses.

Shawn
11-06-2012, 05:31 PM   #7
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QuoteOriginally posted by Shawn67 Quote
I have bought that exact item from that seller, it is certainly a C mount adapter. It is two piece, you *might* be able to get the center section milled down by 5mm which would turn it into a CS mount. I haven't measured if there is more than 5mm of thread available to mill down though.

The other possibility is to buy a D mount adapter and have it drilled/tapped for a 1″×32tpi thread. You may need to *slightly* shim the CS lens on this modified mount though due to slight flange differences between D and CS mount.
I have in fact bought (but not received) both these things, but I don't expect anything I have to modify myself to work until proven otherwise.

QuoteOriginally posted by MysteryOnion Quote
How about a CS to C mount adapter? They seem plentiful too? Would that change the focus distance?
They go the wrong way.
11-06-2012, 05:31 PM   #8
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Well, I'm learning that I might not be snagging CS mount bargains around the Bay anytime soon. Thanks Shawn67!

11-06-2012, 05:55 PM - 1 Like   #9
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Drougge, I have a possibility for you. On pentaxforums there is a person that makes lens mounts from solid aluminum cylinders. If you search "making lenses" threads you will find him. The threads have been fascinating. He is wombat2go. He might make or modify one of these C mounts to work with CS for you. He has made Pk and 4/3 mounts from scratch. CS would be much easier.
good luck
barondla
11-07-2012, 07:59 AM   #10
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QuoteOriginally posted by barondla Quote
Drougge, I have a possibility for you. On pentaxforums there is a person that makes lens mounts from solid aluminum cylinders. If you search "making lenses" threads you will find him. The threads have been fascinating. He is wombat2go. He might make or modify one of these C mounts to work with CS for you. He has made Pk and 4/3 mounts from scratch. CS would be much easier.
That does sound like a possibility. I might try that when (no, not if) I've failed to modify one myself. But I think I'll try to find someone a bit more local first. As you say, it shouldn't really be that hard to do.

Still wondering why the Chinese aren't doing it for me though, seems like I can't be the only one who would buy one (or several).
11-08-2012, 09:40 AM   #11
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QuoteOriginally posted by drougge Quote

The lens on the left is a 25/1.4, available from a variety of chinese sellers. It's very cheaply built.

The lens on the right is a real beauty though. A little big for the Q, but with a great precision feel to the adjustments. Plus it's 5.7-34.2mm f/1.0, so the specs are pretty nice too. The crappy part is that it's CS mount, and for some reason I can't guess at no one makes an adapter. I've had a look though it by holding it up to the camera, coverage is close to good enough, certainly good enough for 1:1 format, depending on zoom it might be good enough for 4:3. Resolution seems semi-decent even at f/1.0, though this is very hard to judge without an adapter.

If I'm lucky I'll manage to modify one of my adapters for it, once they arrive.
I got a black version of the f1.4/25mm - it ain't bad for about US$ 15:-

In my experience with CS (I tried to get a 2,5 mm to focus) you'll have to be careful not to touch the sensor with the back element of the lens if you want to freelens it. Other CS-lenses I've tried to freelens are impossible to focus at any distance when they are "outside" the Q body - . Which is strange when you consider the respective flange focal distances of 17.526 mm for a C-mount and 12.50 mm for CS-mount. The C to CS-mount adapters would add 5 mm to the flange distance of a C-mount making it 22.526 mm. Obviously there is something I don't get here...So maybe I'll try the D-mount (Flange focal distance 12.29 mm) adapter.
It is going to be interesting to hear about the trials and tribulations of the CS adapter project!

Thanks/Erik
C mount - Wikipedia, the free encyclopedia

Last edited by Erich_H; 11-09-2012 at 06:03 AM.
11-08-2012, 01:28 PM   #12
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QuoteOriginally posted by Erich_H Quote
So maybe I'll try the D-mount (Flange focal distance 12.29 mm) adapter.
Sounds like a great option if you can enlarge the opening and re-thread the hole! Much cheaper, too.
11-08-2012, 02:21 PM   #13
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QuoteOriginally posted by Erich_H Quote
In my experience with CS (I tried to get a 2,5 mm to focus) you'll have to be careful not to touch the sensor with the back element of the lens if you want to freelens it. Other CS-lenses I've tried to freelens are impossible to focus at any distance when they are "outside" the Q body - . Which is strange when you consider the respective flange focal distances of 17.526 mm for a C-mount and 12.50 mm for CS-mount.
I didn't actually hold the lens free hand, but put it on the floor and then slid the camera around. Seemed pretty safe (that is, easy to control).

It's perfectly reasonable for lenses to need to stick in to the Q, because the flange is not the rearmost part of the lens. The threads always go behind it, and sometimes the optics go behind the thread. CS mount (unlike C mount) doesn't really promise to leave any specific clearance, because the sensor is expected to be bare. (Well, there's some glass on it, but probably always very thin.)
11-08-2012, 04:17 PM   #14
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Hello Drougge
And thanks to Barondla for the kind words above about my adaptor projects.
If I were doing an adaptor I would first make a diagram like the one I did with assistance from MysteryOnion for adapting Pentax 110 to M43:
https://www.box.com/s/b9319930073aad14e911
It would be necessary to check that the CS register of 12.526 mm can be met with sufficient annular metal in the adaptor.

I see that the CS thread is 1 inch by 32 tpi so it would need to be cut on a USA or old British lathe, or a Metric lathe that has leadscrew gears that can do a pitch of 1/32 inch which is 0.7937 mm. If the CS mount was invented in USA it will have thread angle of 60 degree, if British, probably 55 degree.

The way I do the bayonet mounts is to take a body cap into my (dirty) workshop and measure it as accurately as possible and replicate on the lathe,
leaving enough metal to finely adjust by trial fitting the new adaptor into the camera body.

I think a very high accuracy ( maybe 0.02 mm ) on the register will be needed, especially if a variable focal length (zoom) lens is used.
11-09-2012, 03:11 AM   #15
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QuoteOriginally posted by drougge Quote
I didn't actually hold the lens free hand, but put it on the floor and then slid the camera around. Seemed pretty safe (that is, easy to control).
You can do that with a big lens like that. All (4-5) CS-lenses I've seen live has been really small and cheaply built as opposed to your lens. Did you buy your lenses in Sweden?

QuoteOriginally posted by drougge Quote
It's perfectly reasonable for lenses to need to stick in to the Q, because the flange is not the rearmost part of the lens. The threads always go behind it, and sometimes the optics go behind the thread. CS mount (unlike C mount) doesn't really promise to leave any specific clearance, because the sensor is expected to be bare.
Hadn't thought of that (must be age-related...) but of course you're right.

QuoteOriginally posted by drougge Quote
(Well, there's some glass on it, but probably always very thin.)
Yeah, and you can polish the grease from crappy Chinese CS lenses off of it too. I did...camera still works.
thanks/Erik

Last edited by Erich_H; 11-09-2012 at 06:02 AM.
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