Navitar 6mm F1.4 C mount

On my c-mount adapter the inset portion measures 1 7/16" across. All my c-mount movie lenses are less than that wide, so they all seat into that inset position, and the back of that inset portion is where they sit for the proper flange focal distance.

On the Ultrak security-camera lens, the back portion of that lens is about 1 9/16" across. It's too big to snug into the inset portion of the c-mount adapter. So you'd have to shave down the outer diameter by 1/8", or (preferably) make a new c-mount adapter that has a slightly bigger inset position so these security-camera lenses could fit into it. Warning being, I don't know how standardized that 1 9/16" size is. Do all security-camera lenses abide by that? Or is there variation?

cmount-lens-mount-comparo.jpg
 
Wow Barry you continue to offer so much to this community. Do you guesstimate that I could use a Dremel tool to file down the diameter, or would this interfere with the 1" diameter threads? I don't think it would. Also, perhaps the rear element could be temporarily protected with cellophane.

I'll ask any potential ebay sellers to measure the rear metal surface, but they might not understand which part I mean. Could you upload a photo showing the side profile of two c-mount lenses, 1 that is too big and 1 that's just right for a c-mount to m43 adapter? This way I can describe to a seller where to measure.
 
Here are two c-mount lenses; the security lens on the left, and an old movie c-mount lens on the right.

two-cmount-lenses.jpg

What you'll see is a massive difference in the diameter of the area right behind the mounting threads. The threads are (of course) the same size, but what the threads butt up to is very very different.

On the movie lens, it's very skinny, and so it seats very well into the 1 7/16" recessed portion of the c-mount->m43 adapter. On the security lens, the diameter of the lens immediately adjoining the lens threads is just too big. So what this means is it won't nestle into the 1 7/16" recessed portion at all. The 1 9/16" diameter of the back of the lens makes it run into the surface of the c-mount adapter, so you can only get maybe one turn of lens threads into the threaded portion before the back of the lens runs into the adapter. Which means that the lens isn't fully attaching, and therefore it's too far away from the sensor, and that means you can't get infinity focus.

Whereas on the movie lens, you can see that it easily snugs all the way up to the recessed portion, and therefore it's fully attached and focuses to infinity just fine.
 
This particular lens seems fairly hopeless, or at least I seem to have screwed it up trying to make it work. If someone wants to play with it, I could send it out for the cost of postage (a dollar or two, I suppose).
 
Barry.. how does the movie Cmount lens fair on the Gh2? I think with the teleconverter option I might give some of these vintage lenses a try... Some are too cheap not to give it a whirl and would be a huge bit of nostalgia to use a lens like I did some 20 years ago.. back when film was all i shot..
 
It was one of the lenses I did the 25mm lens comparo with. It was okay in sharpness, ugly bokeh, and a little vignetting. With ETC it wouldn't vignette at all of course.
 
DanDOF said:
Barry and folks, looks like there already is a thinner c-mount adapter for use with wider diameter flange surfaces:
http://www.japanexposures.com/shop/product_info.php?products_id=376

Unfortunately its about $110 USD
Click to expand...


now thats one thin adapter! I found that you need at least 3mm in shaft length after the lens thread to make sure it screws in enough. I have a 1" cctv 25mm f1.4 lens that produces great images but it lacks that 3mm deep 37mm? or smaller diameter step. Something to visually look out for when buying.
 
DanDOF said:
Barry and folks, looks like there already is a thinner c-mount adapter for use with wider diameter flange surfaces:
http://www.japanexposures.com/shop/product_info.php?products_id=376

Unfortunately its about $110 USD
Click to expand...


I have ordered one of these THIN c-mount adapters, for cheap too:
http://cgi.ebay.ca/SUPER-THIN-C-mou...14212?pt=Lens_Accessories&hash=item19c0c1e224
http://cgi.ebay.ca/C-mount-Micro-Fo...97059?pt=Lens_Accessories&hash=item43a40c95e3

I got the one from the second link.
 
Sounds to me like that second one wouldn't allow the security camera lenses to fit; by my calcs 1 9/16" = about 40mm, whereas it's saying it'll allow lenses up to 36.2mm.

Still, for $12 to $20, it's hard to imagine how far wrong you could go by just trying it!
 
pomoville said:
Bought this lens off ebay today, I'm hopeful that with the 2.6x teleconversion on the Gh2, it'll give me a nice, fast wide lens -- I'll let everyone know how it works out, you never know...

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140450453434&ssPageName=STRK:MEWNX:IT#ht_500wt_1140

I believe the seller's got a bunch of them left, I offered $22 and he let me have it.
Click to expand...

Could you please tell me the exact reference of the lens, I can't access to the page due of international restriction.
When you're using the 1:1 function, is it near the vignetting circle or do you loose a little of the frame ?
Thanks
 
That auction says the lens covers 1/2" format. I think the teleconverter mode on the GH2 is close to, and maybe a little bit bigger than, 1/2", so it might indeed cover. It should definitely cover in 720p mode.

6mm isn't terribly wide on a 1/2" chip but it's still wide angle. Consider the 2.6 crop factor of the ETC mode in 1080 mode, and that 6mm lens will have a field of view about equivalent to a 15mm lens on normal mode, or about 31mm in terms of "full frame".
 
Barry_Green said:
That auction says the lens covers 1/2" format. I think the teleconverter mode on the GH2 is close to, and maybe a little bit bigger than, 1/2", so it might indeed cover. It should definitely cover in 720p mode.

6mm isn't terribly wide on a 1/2" chip but it's still wide angle. Consider the 2.6 crop factor of the ETC mode in 1080 mode, and that 6mm lens will have a field of view about equivalent to a 15mm lens on normal mode, or about 31mm in terms of "full frame".
Click to expand...

Well 15mm is not bad, wider than the Lumix 20mm, I'll try to find one not too expensive. Actually I have a Cine-NIKKOR 10mm 1.8, with crop 1:1, it gives exactly the same things than my c-mount Schneider 25mm 1:1.4 with no crop.
 
I doubt this particular lens will ever work out ( even holding it in inside the cam body didn't produce a sharp image). Maybe it was a CS lens misadvertised as C.

If there are 6mm lenses for 16mm it'd likely work out better. I don't think I've ever seen any, though.
 
Yep, I know -- auction said C, and a google search indicated that it was indeed a c-mount, but for whatever reason it wasn't going to work for me.
 
these short, small tv lenses with c-mount are no fun and of little use for the GH-type sensors. I went through the idea last year when I got the GH1, bought 4 c mounts and some converters and gave up on it because even the 9mm f 1.2 will be worse than the pancake 20mm. C-mounts can be great for experimental and artsy stuff but the effect they give can often be done in post as well. Even if you get the correct adapter for infinity focus, nothing beats the costly but excellent 7-14mm lumix for wide angle.
 
The Olympus is cheaper, but it doesn't compare because it's nowhere near as wide. 9mm is not 7mm. The 7mm is crazy wide. It's like the difference on a full-frame camera of a 14mm vs. an 18mm.
 
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