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09-18-2012, 09:29 AM   #1
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Some C-mount questions

I have a Q on the way, and I think it will augment my K-5 well, I'm really looking forward to it. I also have a couple of C-mount adapters and lenses on order, and I have some questions I haven't been able to answer for myself:

1) Most of the info on the internet about adapting C-mount lenses seems to come from the micro-4/3 community, where there are issues with some lenses having image circles smaller than that sensor, but is my understanding correct that it is not an issue for the Q because of the small sensor size?

2) On other camera systems people have had to physically modify C-mount lenses sometimes to fit or to achieve infinity focus due to register distances. I take it these modifications don't need to be done when adapting them to the Q?

3) Unlike my K-5, my understanding is I can't dial-in the focal length of an adapted lens, so I loose shake reduction. Is that the case?

4) In the Pentax non-toy lenses for the Q, there is a shutter in the lens. Adapted C-mount lenses will not have a shutter (like the toy lenses). What is the practical effect or limitation of this, exactly?

5) Do C-mount lenses typically have click-stops on their aperture rings, or is it just smooth since they were intended for video/cinema?

6) On average, how much better are C-mount primes over the zooms? Does the quality of a typical C-mount zoom go down a lot?

7) On my K-mount lenses I almost always use hoods to reduce flare. With the Q, hoods could really reduce portability of the system. How much flare will I be introducing if I use lenses without hoods?

8) Are there good websites out there with info on C-mount lenses in general?

Thanks in advance for any info!

09-18-2012, 12:48 PM   #2
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I would look on flicker for the Q with C-Mount lens, theres tons of em... C-Mounts work great on the Q, you lose SR but hopefully new FW update lets you input the FL for all adapted lenses. Stay away from the c mounts that are for like security cams or the ones they use on those ghost hunting shows, they blow... The old C-mounts that were meant for film are the ones to get, I have a 5.5mm 1.8 switar d mount thats super sharp stopped down and renders colors beautifully, but it's a d mount and vignettes. THere is actually a japanese site with a HUGE list of C mount and D mount lenses with sample images,cant seem to find it right now. you'll also be using the electronic shutter since there is no built in shutter, no big deal really with the c mounts. As for lens hoods some c mounts like the famous kern paillards (the only c mounts I'd actually spend money on) have lens hoods.
09-18-2012, 04:10 PM   #3
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Thanks for the info. The two lenses I bought are TV/CCTV lenses - a Cosmicar (Pentax) and Fujinon... hopefully the quality isn't too bad. They're both primes at least.

If you come up with that japanese site with C and D mount lens info, that'd be great. I did find this excellent explanation of what makes the Bolex Reflex C-Mount lenses different:

The difference between standard and reflex c-mount lenses

BTW, did Kenko ever come out with their C-mount digital camera system?

Kenko announces c-mount camera
09-18-2012, 09:10 PM   #4
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I was going to say the cosmicar/Pentax too, that's a nice lens, has a strong swirly bokeh. The kern paillard 25 i would of picked up if I had the choice but I have the sonnetar for my 25mm needs...

09-20-2012, 03:45 PM   #5
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another thing to be mindful of is that Security/CCTV cameras are often CS Mount - not C Mount. the Registration distances are different despite the fact that the screw size of the mount is the same. C Mount register is 17.526mm versus CS Mount, which is 12.526mm. so using a C Mount adapter with a CS Mount lens will not allow you to focus properly (it won't focus to infinity, if I'm thinking about this correctly).

here is a list of all camera mounts and their registration distances - I found this to be helpful in knowing which lenses can be adapted to various other camera systems: Alphabetical List of Camera Mounts

I have used D Mount lenses on my Q (many of them vignette - which is nice if you're going for that look), however, the adapter wasn't quite the right thickness to allow for proper focusing and I had to unscrew the lens a bit to achieve proper focus at closer distances. so there's definitely a registration problem with the adapter I bought, but I haven't had the motivation to figure that one out yet...

Last edited by emergo; 09-20-2012 at 03:55 PM.
09-21-2012, 09:28 PM   #6
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Thanks for the heads up regarding C mount vs. CS mount.

D mount seems even more obscure, so I'm not sure if I'm ready to delve into it yet... some interesting lenses there though!

I haven't received my mount adapters yet, but my lenses arrived. Good build quality, nearly all metal. The Fujinon has click stops on the aperture ring, the Cosmicar doesn't. Fujinon is 90 degree focus throw, 45 degree on the Cosmicar. Both are well damped. Both have 6 aperture blades.

I couldn't help myself, and ordered a few more, other focal lengths, and a zoom. I'm really curious to see what they're like! I'm not expecting to be blown away necessarily, but I think for the money, I'll end up happy in the end based on my web research.

It seems to me that it will make sense to buy C mount to Q adapters for each lens, so I can swap them on and off the camera easily with the focus and aperture marks lined up properly (the better adapters have set screws to adjust the lens alignment). Is that what people typically do?
09-22-2012, 06:26 AM   #7
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QuoteOriginally posted by nater Quote
It seems to me that it will make sense to buy C mount to Q adapters for each lens, so I can swap them on and off the camera easily with the focus and aperture marks lined up properly (the better adapters have set screws to adjust the lens alignment). Is that what people typically do?
I've been using an adapter without a set screw...I'd love to hear what tips folks have on what C mount adapters have set screws that work well, and how to set the lens so that it focuses at infinity.

I've been playing with a couple C-mount lenses and have another on the way. They're great fun old-school lenses with mediocre optics that make for some creative photography...I hope it's not a C-S mount lens, it's a Fujinon 25-350mm f/3.5 lens (you can find more by searching the net for "C14X25B-SNDS4C"). I bought mine with the usual motorized housing that I'm hoping I can strip off the lens (and/or drive it from an Arduino board setup) as I've seen this lens without the housing for 2x the cost on ePay.
09-25-2012, 08:11 AM   #8
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QuoteOriginally posted by nater Quote
(...)

D mount seems even more obscure, so I'm not sure if I'm ready to delve into it yet... some interesting lenses there though!

(...)
D-mount is the mount of 8mm and Super 8 cameras, hence the vignetting with D-mount lenses on Q: Q's sensor size is 4.55x6.17mm whereas 8mm exposed area is 3.30x4.50mm and Super 8 is 4.01x5.79mm.

C-mount is the mount of 16mm and Super 16 cameras and many CCTV cameras.

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