Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
12-21-2006, 03:59 PM   #1
Veteran Member
Duh_Vinci's Avatar

Join Date: Nov 2006
Location: Virginia, USA
Photos: Albums
Posts: 1,301
Stop down method on K-Body (m42 and manual K)

I've read just about every thread I could find here on m42 and older K mount manual lenses, but I still have question regarding fitting it and working with aperture ring in the manual mode on K10D (or alike)

I got couple of lenses for next to nothing (both 135mm 2.8 MCs), one K mount, one m42 mount...

K mount - I think I get the idea: when not in "A" position, blades close and open (and stay there) as I move the aperture ring on the lens, so the true aperture I selected is where the lens blades would stay...

m42 mount - that little pin... Blades do the opposite - close or open depending on the aperture I select on the ring, but only when that pin is depressed. I have not recieved the adapter ring yet, but what puzzles me with m42, how is this pin depressed once the lens is on the camera? Is it done via some drive mechanism in the camera body?

Thanks for puting up with the newbie to Pentax


12-21-2006, 04:34 PM   #2
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 49,948
To be able to use the aperture ring on M42 lenses, you have to set the diaphragm to manual using the slider on the lens.

Select the aperture size, and then get the camera to meter the light and set a shutter speed:

Adam Webmaster (Site Usage Guide | Site Help | My Photography) server and development costs are user-supported. You can help cover these costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

12-21-2006, 05:38 PM   #3
Veteran Member
Duh_Vinci's Avatar

Join Date: Nov 2006
Location: Virginia, USA
Photos: Albums
Posts: 1,301
Original Poster

Thanks for the reply (though the link does not work) - this is what I found very usefull (not sure if its from the same thread):

QuoteOriginally posted by i.glisin Quote

2) Using AE-L button sets correct shutter speed for set aperture: point at the target, hit AE-L and camera will stop down, meter, and adjust Tv. It all takes just a moment! (I use this method 99% of time.) Point at various subjects and keep hitting AE-L to see how it works.
I guess my actual question is to how is the pin on M42 activated within the camera?

More specific, if I wanted to use the M42 lens with the set of non-auto extension tubes on K10D, the tube set (the part that mounts to the M42 lens) would have to have an inner lip that less diameter than the actual thread, where the pin of the lens will push itself against that lip and remain in that position at all times)? Then the adapter M42 to K would be mounted to the other end of the tube to be coupled with the body?

Thanks again!

12-21-2006, 06:14 PM   #4
Veteran Member

Join Date: Sep 2006
Location: Virginia Beach VA USA
Photos: Gallery
Posts: 1,364
The pin on a M42 lens has no effect with a K mount body. You must open and close the aperture manually to focus and expose.
In addition, if your lens has the Auto/Manual switch, you should move the switch to manual.

12-23-2006, 01:20 AM   #5
Veteran Member
eurostar's Avatar

Join Date: Dec 2006
Location: Albareto, Italy
Photos: Gallery
Posts: 819
The pin is just for old Spotmatic cameras. On the K mount Pentax you can use it just in stop-down.

  • 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!
aperture, blades, camera, k-mount, lens, lenses, m42, pentax lens, pin, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Method of manual focus Capslock118 Troubleshooting and Beginner Help 10 04-29-2011 06:44 AM
Manual apature stop-down metering? Chonker Troubleshooting and Beginner Help 34 03-23-2011 01:23 PM
Cannot stop down manual lens for some reason SamWarrick Troubleshooting and Beginner Help 28 09-06-2010 10:21 AM
f stop input for manual lenses? axl Digital Processing, Software, and Printing 6 06-30-2010 05:09 AM
Macro: Handheld, Manual Focus, Manual Stop-Down Mike Cash Post Your Photos! 2 06-19-2008 07:14 AM

All times are GMT -7. The time now is 04:35 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]