Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
01-19-2016, 07:15 AM   #1
Junior Member

Join Date: Sep 2015
Posts: 25
automatic diaphragm

Hi, I recently got pentax 67ii body and while reading on the lenses, I came across the term automatic diaphragm.
I was wondering what this means in terms of what is automatic about the diaphragm

01-19-2016, 07:50 AM   #2
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 43,114
It means that the camera automatically stops the lens down to the aperture setting selected on the aperture ring when you press the shutter button.

On earlier bodies, you would have to stop down to shoot/meter after composing, then open the aperture back up afterwards to brighten the viewfinder.

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

01-19-2016, 08:58 AM - 1 Like   #3
Senior Member
Ontarian50's Avatar

Join Date: Mar 2015
Posts: 244
+1 to Adam's reply.

If there's one thing consistent in photography is the term "automatic".

I have here on the desk an Asahi Pentax S2, with its 55mm "Auto Takumar". Today's photographer sees nothing automatic about this camera at all. It didn't even have a light meter. But no doubt many a great frame was ruined by forgetting to stop down a pre-set lens to its taking aperture before tripping the shutter. Having a lens that snapped that aperture down as the mirror went up was considered "automatic" at the time.

Later we saw SLRs with automatic exposure, either controlling the aperture automatically with the light, or the shutter speed. These were later dubbed "semi-automatic" cameras when fully programmed exposure SLRs arrived on the scene. Today, all these are often called manual cameras, because they don't have autofocus.

I can only speculate, but I can think that in the future, today's cameras will be dubbed "manual" because they don't fly along beside us and record everything we see
01-19-2016, 12:07 PM   #4

Join Date: Feb 2009
Location: Arizona
Posts: 911
The Auto function on the lens is mechanical as Adam has said but it also has a metering function. When using a metered body (AE or TTL prism) the Auto function allows wide open metering, even though you may have no intention of shooting wide open. This is due to the connection between the meter and the aperture ring.


  • 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, 645z, camera, diaphragm, medium format
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
A series and auto diaphragm lens launch wildman Pentax SLR Lens Discussion 19 07-14-2015 09:35 AM
Diaphragm wide open no matter what yannouchka77 Pentax SLR Lens Discussion 12 05-19-2015 06:07 AM
Aperure diaphragm design? max_pyne Pentax SLR Lens Discussion 10 12-07-2014 02:50 PM
Pentax diaphragm lever Jump Pentax SLR Lens Discussion 17 12-06-2014 07:18 AM
K2 diaphragm ring problem JuanEstrada Pentax Film SLR Discussion 5 05-05-2014 06:07 PM

All times are GMT -7. The time now is 11:59 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]