Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
08-12-2011, 10:45 AM   #1
Forum Member

Join Date: Oct 2008
Location: Shenzen/ Hongkong
Posts: 71
C mount > M43 > K/M42

is this possible? any issues if setup this way?

C mount > M4/3 mount > PK/M42 mount would that work?

08-12-2011, 11:00 AM   #2
Veteran Member

Join Date: Mar 2011
Photos: Gallery | Albums
Posts: 303
I'm not sure whether it would technically work (I don't see why not), but the image circle covered by C-mount lenses is somewhere between 8mm and 16mm in diameter, and an APS-C sensor is 16x24mm. Therefore, from that lens, any image that you would get would likely not fill the frame -- You would get images that have a circle with the image in the middle and black everywhere else in the frame.
08-12-2011, 11:11 AM   #3
Forum Member

Join Date: Oct 2008
Location: Shenzen/ Hongkong
Posts: 71
Original Poster
Oh i see, so it's like some type of lens used on a FF body that has that circle/ lomo effect.
thanks for the info.

i ask since there are no C to PK mount adapter out there.
08-12-2011, 02:29 PM   #4
Veteran Member

Join Date: Dec 2007
Location: Prague
Photos: Gallery
Posts: 1,199
There will probably be one for Pentax Q.

08-12-2011, 02:33 PM   #5
Veteran Member
RioRico's Avatar

Join Date: Jun 2008
Location: Limbo, California
Posts: 11,263
C-mount, used for cine-video cams, has a 25mm thread. You can find a 25-42mm step ring (actually a disc) online for a few bucks. I have one, which I thread into an M42-PK adapter to mount on my Pentax dSLR. But it is useless there.

This has to do with register aka flange-focal distance, the distance from the back of the lens to the camera frame (film or digital). The Pentax register is 45.46mm. The C-mount register is 17.526mm. Assuming they can be made to fit, longer-register lenses can reach infinity focus on shorter-register camera bodies, but not vice-versa. I put a 50mm C-mount lens on my camera. Its furthest focus is about... 50mm, two inches.

This is the basic rule: C-MOUNT LENSES ON DSLRS ARE ONLY GOOD FOR CLOSE-UPS. No Lomo effect, no vignetting -- just ultra-closeup. Don't bother. Or get a Sony NEX (register= 18mm) where C-mount lenses can at least be used for portraits. Or wait for the Q (register= 9.2mm). Have fun!
08-14-2011, 08:24 PM   #6
Forum Member

Join Date: Oct 2008
Location: Shenzen/ Hongkong
Posts: 71
Original Poster
thanks RioRico

I guess I'll put my C mount to PK mount to rest & just get other M42's lol

  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
k-mount, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: FotoDiox K-mount to m43 mount adapter w/ aperture control deejjjaaaa Sold Items 3 08-04-2011 10:06 AM
For Sale - Sold: 4 K mount lenses and 1 M42 screw mount lens (US/CAN) alanjoke Sold Items 8 07-20-2011 06:05 AM
Hey new here, quick question, is this K mount or M42 Screw Mount? Lulerfly Pentax SLR Lens Discussion 8 11-02-2010 11:58 PM
K mount to m42 screw mount epqwerty Troubleshooting and Beginner Help 10 03-20-2010 07:47 PM
For Sale - Sold: Tamron 300mm 5.6 m42, Sears 200mm 3.5 m42 mount. telfish Sold Items 13 02-28-2010 10:30 AM

All times are GMT -7. The time now is 10:03 PM. | See also:, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]