Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
01-19-2013, 02:21 AM   #1
Senior Member

Join Date: Oct 2012
Posts: 101
DIY crop mode?

I would like to try mounting a "small format" (eg K-mount, Canon EF, Nikon FX etc) lens on a Pentax 645 or other MF camera with the hope this would work similar to the "crop mode" feature of the latest Canon, Nikon and Sony DSLRs that enable mounting of legacy APS-C mount lenses on their full frame bodies albeit only using a small part of the sensor. Do you know of any adapter that can do this?

01-19-2013, 03:32 AM   #2

Join Date: Jun 2010
Location: North Zealand, Denmark
Photos: Gallery | Albums
Posts: 1,516
Not really practical:

Registration distance, 645 Mount = 70.87mm
Registration distance K-mount = 45.46mm

That is, the image formed by a K-mount lens placed in level with the 645 flange would form about 2 cm in front of the 645 sensor. In other words, you will need some optical element that can carry the image over that extra distance.

It works with FX and DX because these cameras have the same registration distance.
01-19-2013, 05:31 AM   #3
Senior Member

Join Date: Oct 2012
Posts: 101
Original Poster
thanks for clearing this up

  • 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!
camera, canon, medium format, nikon
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Will Pentax FF have a APSC crop mode?? COULDBE2 Pentax SLR Lens Discussion 22 10-29-2012 06:33 PM
Night To crop or no to crop...? esman7 Photo Critique 17 01-17-2010 08:28 PM
Does the "crop factor" just crop? jboyde Troubleshooting and Beginner Help 8 01-03-2010 08:18 AM
To crop or not to crop ? fredg Post Your Photos! 2 09-20-2009 02:02 PM
To crop or not to crop Christian Post Your Photos! 12 05-11-2007 04:08 PM

All times are GMT -7. The time now is 06:21 AM. | 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]