Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
05-21-2008, 12:56 PM   #1
Veteran Member
pentagor's Avatar

Join Date: Dec 2007
Location: Ljubljana, Slovenia
Photos: Gallery
Posts: 473
M lenses and metering

So here is the thing:

Today I tried my M 50/1.7 lens on my MZ-7 film SLR. I put the camera into Av mode and turned the aperture ring on the lens. Surprisingly, the camera responded with different shutter speed values. What am I missing here? The DSLR does not do that, because the aperture is wide open until you press the shutter release or A/E lock button in M mode.

I know, that when you use M42 lenses, you actually change the aperture opening when turning the aperture ring. But of course you notice this as the viewfinder is getting darker when stopping down the lens.
How in the world does the MZ film camera know, that the aperture has been changed? I didn't notice any darkening of viewfinder image when I stopped down the lens.
Can anyone explain this to me, please?

05-21-2008, 01:50 PM   #2
Veteran Member
KjetilH's Avatar

Join Date: Mar 2008
Location: Oslo
Photos: Gallery
Posts: 309
The MZ-7 has the original KAF2 mount. The digitals have a 'crippled' version, which basically means they are unable to read the aperture value mechanically, presumably through the aperture lever.

In theory, if the digital bodies were told the aperture wide-open and the aperture when stopped down, it didn't have to check the exposure stopped down.
(Which is what the A lenses do.)

  • 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, camera, film, k-mount, lens, lenses, mode, notice, pentax lens, shutter, slr lens, viewfinder
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
K-x Stop-down metering with m-42 lenses Bazwell Pentax DSLR Discussion 8 11-20-2009 12:57 PM
Metering with M-lenses on the K-7 blende8 Pentax DSLR Discussion 18 06-02-2009 12:45 AM
K10D metering: different lenses annod Pentax DSLR Discussion 17 02-09-2009 05:15 PM
Metering with M/K Lenses On The MZ-50/ZX-50 (and other questions) lithos Pentax Film SLR Discussion 3 09-04-2008 10:04 PM
Lenses and Metering arbutusq Pentax SLR Lens Discussion 1 04-16-2007 12:25 PM

All times are GMT -7. The time now is 11:20 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]