Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
07-21-2014, 05:47 AM   #1
New Member

Join Date: Jul 2014
Posts: 10
canon lenses on Pentax 645d

Hi does anyone know if you can get an adapter to use a canon lens (ie my excellent 70-300 zoom) on a 645d please? Just an idea :}

07-21-2014, 07:48 AM   #2
Site Supporter
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Oregon Cascades
Photos: Gallery | Albums
Posts: 11,674
Even if there was such an adapter the lens would not cover the full image circle of the 645d, so you would get extreme vignetting. Maybe I'm missing something but I do not think this would work.
07-21-2014, 07:51 AM   #3

Join Date: Jul 2009
Location: Seattle
Posts: 7,611
Do you know if that 70-300 has a large enough image circle to be used on a 645D?
07-21-2014, 07:57 AM   #4
Loyal Site Supporter
Loyal Site Supporter

Join Date: Jun 2009
Location: Tumbleweed, Arizona
Photos: Gallery | Albums
Posts: 5,314
registration distance is going to be a problem.
  • Pentax 645 70.87mm
  • Nikon 46.5mm - and Canon is even shorter
The physical diameter of the mount is substantially different. The difference in sensor size with the 645 being 60% larger and nearly double the distance away - I see as a problem that will be difficult to solve.

Last edited by interested_observer; 07-21-2014 at 10:49 PM. Reason: for some reason pulled the Nikon registration distance and not the Canon - just noted this
07-21-2014, 08:17 AM   #5
Otis Memorial Pentaxian
Loyal Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 30,492
Forget the image circle unless you are interested in an extreme macro zoom. The registration distance for the Pentax 645 mount is almost twice that of Canon.

07-21-2014, 10:00 PM   #6
Veteran Member

Join Date: Mar 2007
Location: Christchurch, New Zealand
Photos: Gallery
Posts: 617
QuoteOriginally posted by greatgable Quote
Hi does anyone know if you can get an adapter to use a canon lens (ie my excellent 70-300 zoom) on a 645d please? Just an idea :}
Simple answer - NO. The registration distance, which is the distance from the mounting flange to the sensor/film plane is smaller for Canon lenses.

This means you would need to mount the Canon lens about an inch (25mm) inside the Pentax 645 mount where it would be hit by the mirror.

Not going to work.


07-22-2014, 07:27 AM   #7

Join Date: Jul 2009
Location: Seattle
Posts: 7,611
This thread has a link to a picture of someone who mounted a Nikon 300/2.8 to a Pentax 6x7.

  • 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!
645d, canon, canon lenses, lenses on pentax
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Adapter for using Pentax 67 lenses on a 645D Photodana Pentax SLR Lens Discussion 4 06-25-2014 02:49 PM
Pentax 67 Lenses on the 645D? uintaangler Pentax Medium Format 34 11-14-2013 02:38 PM
Using Pentax M Lenses on Canon DSLRs Peter Murphy Visitors' Center 6 10-28-2013 11:58 AM
Using canon lenses on pentax k Reptilezz Pentax K-5 7 08-07-2013 11:46 PM
Switching to Canon 5D, advice needed on adapting Pentax lenses on canon camera hangu Photographic Technique 4 08-19-2010 09:09 PM

All times are GMT -7. The time now is 06:25 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]