Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
06-18-2012, 10:57 AM   #1
New MF lens user
Guest




Aperature setting on M42 MF lens

Hello all,

I have recently aquired a K5 with two kit lenses. Soon after I got LBA and now I also have 3 manual Chinon K mount lenses (the standard 28, 50 and 135). Having great fun with the aperature ring in manual mode. I am using the green button for metering. Then, temporarily, the aperature lever closes the aperature for metering. Works very nice and is pretty fast if you are used to it. For the remainder of the time, the aperature is wide open so you can properly focus and compose through the viewfinder.

Now I got an M42 adapter and considering some M42 lenses. Of course, they do not have the aperature lever in the right place. I saw on some pictures a pin which supposedly controles aperature in a similar way. However, this one is not controled from Pentax cameras.

Are there any tips on using M42 lenses and metering? Can metering be done easily with the proper aperature, while the aperature stays open for composition and focusing?

I have seen some M42 lenses with a mystery button near the aperature ring. Does this do the same trick? How can I be sure? Are there any other things to watch?

06-18-2012, 11:02 AM   #2
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 5,002
If the lens has an "auto-man" or "A-M", switch, then put in on M -- now the aperture will close down with the ring. Set the camera on Av mode, and no need for the green button -- just set aperture to desired and shutter speed is set automatically. (All auto modes will become Av mode.) ISO can either be fixed or set on auto. The aperture pin is never used. If it has no switch, the pin can be glued down if you don't mind the permanent nature of that.

So you want to focus with the lens wide-open, stop down to desired aperture, and fire.

See this thread for full details:

https://www.pentaxforums.com/forums/pentax-lens-articles/110657-how-use-meter...k-x-k-7-a.html
06-18-2012, 12:19 PM   #3
Veteran Member
RioRico's Avatar

Join Date: Jun 2008
Location: Limbo, California
Posts: 11,264
QuoteOriginally posted by New MF lens user Quote
Are there any tips on using M42 lenses and metering? Can metering be done easily with the proper aperature, while the aperature stays open for composition and focusing?
As von said, this can only be done indirectly. If the lens has an M/A switch, you can compose with the switch set to A, then flick it to M to stop-down for metering and exposure.

QuoteQuote:
I have seen some M42 lenses with a mystery button near the aperature ring. Does this do the same trick? How can I be sure? Are there any other things to watch?
Some very few M42 have a stop-down button. I see this on some German lenses, which may have a shutter-cable socket for stopping-down the lens when used on bellows. In my hot hands at this very moment is a Schneider-made Isco Westron 35/2.8, one of my pixie-dust lenses. It doesn't exactly have an M/A switch, but does have an open-iris lever|switch and a stop-down cable socket|button. I think I've seen what look like stop-down buttons on other lenses but I can't be sure. Your "mystery button" may just be an M/A switch.
06-18-2012, 03:53 PM   #4
dms
Site Supporter




Join Date: Aug 2011
Location: New York, NY
Photos: Gallery
Posts: 1,623
If you use zone focusing, with the MF lens (of 35mm or shorter) you may find it often faster/preferable to using a non A K lens. To start set lens at the hyperfocal distance for 1 stop more open than you actually use. e.g., for a 28mm lens set at f/16, use the hyperfocal distance for f/11 (10 feet) and 5 feet to infinity will be in good focus.

06-18-2012, 06:47 PM   #5
Veteran Member
RioRico's Avatar

Join Date: Jun 2008
Location: Limbo, California
Posts: 11,264
More about zone focus: It's a way to exploit the DOF of a lens. If the zone extends to infinity, it's called hyperfocus. This works best with wider (<40mm) lenses with long focus throws. Longer lenses and shorter throws make the DOF scales inscribed on old MF lenses very difficult to use. I normally use zone focus with 21-24-28mm lenses, although I have some 50-55mm glass with long throws that do quite well.

As @dms said, adjust your reading by 1 stop -- or more. If I'm doing hyperfocus, I'll adjust by about 1.5 stops. So if I have the aperture set to f/16, I'll set the infinity mark to just inside f/11, centered around f/9.5 or thereabouts. This ensures that infinity will be sharp.
Reply

Bookmarks
  • 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!
aperature, button, camera, lenses, lever, m42, pentax help
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
15+ aperature blade lens listing adrianpglover Pentax SLR Lens Discussion 20 02-07-2015 04:36 PM
aperature placement in lens design ncallender Pentax SLR Lens Discussion 25 06-10-2014 05:04 AM
Cheap auto focus/aperature lens? clockwork247 Pentax SLR Lens Discussion 3 11-28-2010 07:37 PM
K10D and aperature ring setting WildSioux Pentax DSLR Discussion 2 03-20-2007 09:49 PM
SMC 50 1.7 aperature setting question... clarenceclose Pentax SLR Lens Discussion 13 03-07-2007 03:17 PM



All times are GMT -7. The time now is 10:59 AM. | See also: NikonForums.com, CanonForums.com 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?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top