Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
02-02-2011, 09:17 AM   #1
Senior Member

Join Date: Jun 2010
Location: Bothell, WA
Posts: 103
Playing with aperture: am I doing it wrong?

So I recently spent a day walking around trying out my new (to me) Vivitar 135 f2.8 m42. Great lens, I really enjoy it so far. However, I'm wondering if my experimental technique is off. Here's what I'd do.

I normally shoot a fast 50 wide open indoors at night, so I was happy to get the chance to try out some of the smaller apertures a little more. But when I'd put it down to f11 or smaller, the lack of light coming in made focussing really difficult. So I'd throw the aperture to 2.8 then compose and focus, rotate the aperture down to whatever stop I wanted, then do the green button for a shutter speed and take the shot. I found that my body with this lens tends to go one stop too slow and over expose, so I'd usually then adjust the shutter speed one stop faster and take a second picture.

In any case, when using screw mount lenses is using the widest aperture to compose and focus, then turning down to a higher f-stop for metering and taking the picture a bad thing? It seemed to work pretty well for me, but I don't want to develop bad habits.

02-02-2011, 09:29 AM   #2
Loyal Site Supporter
Loyal Site Supporter
boriscleto's Avatar

Join Date: Dec 2009
Location: North Syracuse, NY
Photos: Gallery
Posts: 15,879
You're not doing anything wrong.
02-02-2011, 09:29 AM   #3
Loyal Site Supporter
Loyal Site Supporter
ismaelg's Avatar

Join Date: Apr 2009
Location: Puerto Rico
Photos: Gallery
Posts: 2,053
That's how older pre-set lenses used to work. Your technique is good, but sorry, you can not file for patent.
On those lenses (I have 2 of them) the aperture has 2 rings. One to set the desired aperture and another one that opens the lens fully for focusing and composition. When you are ready you close this second ring and it stops at the aperture set by the first ring.
Glad to see older lenses been enjoyed as intended!

02-02-2011, 09:41 AM   #4
Site Supporter
Site Supporter
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 16,761
You are not doing anything wrong, but you can be more efficient.

You do not say what body you are using so there could be "translation errors" in terms of commands

first, You should be using EV compensation, if the lens is always giving over/under exposure. This is much easier than clicking up/down by a stop after picking exposure

To my knowledge, only the K10D does not provide EV compensation in manual, the *istD and K7D do for sure.

Second, Av mode is much more convenient, than manual for M42 lenses because it continually sets the shutter speed as you half press the shutter release. Unless you really want a specific exposure (aperture and shutter speed) this is the way to use M42 lenses.

Lastly, and others have mentioned this, the auto manual switch on most M42 lenses switches from opened to stopped down, so focus in Auto, and shoot in manual this will always stop down to the desired aperture. Preset lenses are even easier, since you can preset the aperture and turn the ring to stop down to the preset.

K mounts are different because you can;t use Av mode (except wide open) so you are stuck with the green button.

BTW, if you don;t want to change the setting but see the exposure, use the DOF preview as it activates the metering in the viewfinder at the same time


  • 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, focus, lens, pentax help, photography, picture, shutter
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Machinery More playing with new K-x hangman43 Post Your Photos! 2 11-06-2010 01:21 PM
Abstract Just playing around charliezap Post Your Photos! 1 03-25-2010 12:25 PM
Constant Aperture vs Variable Aperture Netsoft Pentax SLR Lens Discussion 13 01-11-2010 07:29 AM
Use of Aperture-Ring 43mm/1.9 -> no aperture data Deimo Pentax SLR Lens Discussion 7 06-24-2009 03:25 PM
K100D registers wrong aperture Timarete Pentax DSLR Discussion 18 06-07-2008 12:59 PM

All times are GMT -7. The time now is 12:40 AM. | 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]