#Arkive TC: "C-mount" lenses for M4/3 bodies

nigbat · Apr 4, 2017

Got hold of one of the thin adapters, which at least enables me to mount the lens (albeit further away from the sensor than required).

I can't focus further away than about a foot, but the optics look pretty good, even in the corner when stopped down, as in the third shot (first two wide open). I will have to see if I can do something about the ugly brass ring at the back of the lens, in order to get it mounted properly ...

GnarlydogOZ · Apr 4, 2017

nigbat said:
Got hold of one of the thin adapters, which at least enables me to mount the lens (albeit further away from the sensor than required).

I can't focus further away than about a foot, but the optics look pretty good, even in the corner when stopped down, as in the third shot (first two wide open). I will have to see if I can do something about the ugly brass ring at the back of the lens, in order to get it mounted properly ...

seems to have a great bokeh; it would be worth working on it to get it a bit closer to the sensor

nigbat · Apr 7, 2017

Quickly removing the plate which incorporates the C-mount, it's fairly clear that the outer edge of the plate below it which holds the body of the lens (and is the bit that is too wide for C-mount adapters) serves little purpose.

As you can see, four screws attach the plate to the rest of the lens, and adjacent to them are the five holes for the screws which attach the mount. The five (empty) holes around the edge appear to serve no purpose.

If I had a lathe, I could detach this part and remove a few mm from the rim...

GnarlydogOZ · Apr 7, 2017

nigbat said:
Quickly removing the plate which incorporates the C-mount, it's fairly clear that the outer edge of the plate below it which holds the body of the lens (and is the bit that is too wide for C-mount adapters) serves little purpose.

As you can see, four screws attach the plate to the rest of the lens, and adjacent to them are the five holes for the screws which attach the mount. The five (empty) holes around the edge appear to serve no purpose.

If I had a lathe, I could detach this part and remove a few mm from the rim...

I am of the opinion that permanently altering the lens is my last resort and I always try an easier route.

From your images it seems that you do indeed gain a lot of clearance by unscrewing the chromed plate with the C-mount thread (25mm). I would be inclined to simply glue, with modified epoxy (JB Weld or similar), a C-mount to Micro 4/3 adapter directly to the lens, possibly with the need to shim a bit since you bring the lens too close to the sensor?

And while a lot of people get weak in the knees by hearing glue lets remember that it is reversible: a hot hair drier/heat gun will soften the glue enough for easy removal.

Curios to see how you modify this lens and make it work

nigbat · Apr 7, 2017

Sadly I'm not sure that will help.

The problem is the sheer width of the revealed part, which I don't think will sit any deeper in the adapter; if it were narrower, the (here removed) C-mount part would screw deeper into the adapter, so dispensing with that would not help.

(But I quite agree with you that irreversible modification is a last resort.)

nigbat · Feb 16, 2018

New acquisition, priced significantly less than they normally go for. The lens is a bit loose - there's a little play between the front and rear - which could explain why it was going cheap.

First test shots, wide open, look rather good, though (touch of CA, but nothing disturbing):

The rear element of the lens is considerably wider than the C-mount, and if it were fitted with a wider throated mount looks as though it would happily cover an ASPC sensor.

nigbat · Feb 16, 2018

Closest focus is supposed to be around 1m, but I can't get my copy to go closer than around 2m (which again suggests it might have been opened up and put back together less than expertly)...

Using a 5mm C mount extension ring, that's not a problem. This shot is stopped down to f4 - showing the 12 aperture blades. Impressive detail.

nigbat · Apr 6, 2018

Picked up my third Canon TV 16 lens. Tiny lens, which looks quite good on the camera, and has very smooth focus throw.

It has considerably more distortion (barrel), and field curvature than the 50mm and 100mm, which is to be expected, but quite sharp wide open in the centre, and vignettes less than some other 25mm cine lenses. 10 aperture blades.

nigbat · Apr 6, 2018

Outdoor test shot, @ f1.4.

yatakk · Apr 6, 2018

Thank you for the info about this lens. Could you try to achieve some sunstars with this lens stopped down?

nigbat · Apr 12, 2018

Sorry, haven't had time, but I'll try to get around to it.

Meantime, here's a cat pic with the Ivotal 25/1.4:

nigbat · Apr 19, 2018

yatakk said:
Thank you for the info about this lens. Could you try to achieve some sunstars with this lens stopped down?

This do ?

Taken at f22 (note the vignette is harder stopped down).

yatakk · Apr 19, 2018

nigbat said:
yatakk said:

Thank you for the info about this lens. Could you try to achieve some sunstars with this lens stopped down?

Click to expand...

This do ?

Taken at f22 (note the vignette is harder stopped down).

Thank you! I had hoped for better defined sunstars with the 10 blades. I think you saved me for some money

nigbat · Apr 20, 2018

In my quest to explore the C mount lenses (and possibly impoverish myself...), I acquired what I think is a machine vision version of the lens.

It has the benefit of being considerably cheaper than the cine lenses, but had first to be removing from its motorised housing, which took a while, as it was not immediately apparent that the rear plate of the housing would unscrew (in the end, the method was a bit like removing a retaining ring at the front of a lens, but more work...).

Here's a shot of the lens on camera, with the empty housing behind:

I managed to take a shot using the lens still in the housing by dint of a C-mount extension tube, which didn't allow me to focus further than a few cm:

Once extracted from the housing, the adapted lens will focus readily to infinity.

Couple of test shots with the usual target showing bokeh wide open and stopped down a bit (which reveals this version has only four aperture blades... though I think it's the nicest square bokeh I've seen.

And a flower shot:

E Dinkla · Apr 20, 2018

I have two Xenon 50mm 2.0 samples of that type. Does magic on M4/3. The square aperture includes a shutter too for the video tube protection of that camera type. It can be switched off in the lens.

Met vriendelijke groet, Ernst
No photographer's gear list is complete without the printer mentioned !

nigbat · Apr 20, 2018

I think I know the one you mean.... another one to add to my wanted list.

E Dinkla · Apr 20, 2018

This one;

Loading…

www.pigment-print.com

Met vriendelijke groet, Ernst
No photographer's gear list is complete without the printer mentioned !

DiffractionLtd · Apr 20, 2018

Schneider 25mm f/0.95 Xenon:

Zeiss 25mm f/1.4 Tevadon:

Fujinon 25mm f/1.4:

nigbat · May 1, 2018

Acquired a (slightly beat up) copy. One thing I don't like about it is that it doesn't focus very close (somewhere around 1.5m) - the test shots below required the use of a 5mm extension tube. The lens also seems to focus a bit beyond infinity.

5mm is probably a bit too much, but is the shortest C-mount extension tube you can get because of the design of the mount. I'd really like a C-mount adapter which is about 2.5mm thicker than normal to give the same effect as a 2.5mm extension, which other than using a very thick shim (which might prevent the lens mounting very securely) isn't otherwise possible.

nigbat · May 2, 2018

Any idea how to get at the aperture of the Kodak 4.5 inch f4.5 Anastigmat ?

One of the aperture blades is popped out of true. I can get the front of the lens off, and can unscrew the aperture ring, but this doesn't allow me access to the rear of the aperture mechanism. DO I have to totally dismantle the lens, or is there a simpler way ?

Anyone ?

#Arkive TC: "C-mount" lenses for M4/3 bodies

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