Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
06-03-2010, 08:19 AM   #16
Inactive Account

Join Date: Mar 2007
Location: Nove Zamky, Slovakia
Photos: Gallery | Albums
Posts: 7,181
QuoteOriginally posted by olenl Quote
You are right.

My mistake was that I judged by my impressions with old 135 mm lens. Since I happened to have pointed it to the lighter areas, it received more light than wide kit lens, thus it was "faster". I have just checked with relatively the same light and those fixed lenses give similar shutter with the same aperture.

Another problem is that k-x's expometer seem to be way off with those lenses, I always have to either lower or raise the exposition (more often, raise) to get correct exposure. I also can't make flash work right with them but it's offtopic.
I don't know about K-x but with K10/20 and older bodies it was focusing screen that was to blame to have offset the exposure. With K-7 this was somewhat fixed and it's exposures with manual lenses are better than previous bodies but still not as good as with *istD and older (film). There was a member who had a go on *istD's focusing screen and fitted it into his K10D. The exposures were practically correct on any given f stop.

As it is now (at least with K10/20) correct exposure is obtained between f2.8 and f4... at anything faster than f4 my camera underexposes, and on f stops smaller than 5.6 it overexposes.... The margin of error increases the further from optimal f stop I move.... I assume your K-x may be the same....
As far as the flash goes, it will always fire at full power since there isn't any body/lens communication. You can calculate the f stop for correct exposure by finding out the Guide Number of your flash and eyeballing the distance to subject


  • 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!
40mm, aperture, criteria, da, f/2.8, k-mount, lens, light, macro, pentax, pentax lens, slr lens, smc
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Sports Help Selecting ONE ajtour Post Your Photos! 6 03-15-2010 05:08 AM
Help selecting the lens Please! Mystic Pentax SLR Lens Discussion 9 05-18-2009 01:58 AM
Help selecting... rmtagg Photographic Technique 17 05-30-2008 09:34 PM
Need help selecting a printer Ed in GA Photographic Technique 4 09-28-2007 07:49 AM
Help selecting first lenses Chilichoco Pentax SLR Lens Discussion 14 05-14-2007 01:11 PM

All times are GMT -7. The time now is 03:41 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]