Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
06-06-2008, 07:07 AM   #16
Senior Member

Join Date: Oct 2007
Location: Wisconsin
Posts: 273
QuoteOriginally posted by ftpaddict Quote
Technically, it's 1/4 a stop. You decide if that's important to you or not.
Actually, it's 1/6 stop.

06-06-2008, 07:31 AM   #17
Veteran Member

Join Date: Nov 2006
Location: Hong Kong
Posts: 1,934
F-numbers Maths!

QuoteOriginally posted by JMS Quote
Actually, it's 1/6 stop.
Yes, you're right. To be more exact, *if* we believe the f/1.7 to be exactly 1.7000000... and the f/1.8 to be 1.8000000...., the difference is actually 0.1649243202 stop.

However, the round up is practically not applicable for most of the time, unfortunately. It is because in real, f/1.4 is f/1.414213562 theoretically and f/1.7 is f/1.68179283 where as f/2 is exactly f/2.000000.... and so on!

Last edited by RiceHigh; 06-06-2008 at 09:40 AM. Reason: To correct a calculation error
06-06-2008, 08:26 AM   #18
Veteran Member
ftpaddict's Avatar

Join Date: Jan 2008
Location: Yurp
Photos: Gallery
Posts: 4,669
QuoteOriginally posted by JMS Quote
Actually, it's 1/6 stop.
Well dang. That's why I didn't go to math school.
06-07-2008, 12:59 PM   #19
Veteran Member
Big Dave's Avatar

Join Date: Jan 2008
Location: San Antonio, Texas
Photos: Gallery
Posts: 547
I beleiving that the note applies to matrix metering which requires the appeture position lever to connect to the camera. The DSLRs use the crippled KA mount. No connection, just the electrical contacts and diaphram lever.


QuoteOriginally posted by joefru Quote
At the bottom of that page, it says there will be no effect for Pentax dSLRs. Maybe they read the aperture differently? And I must have been mis-remembering, because I just took a shot with my K10D/FA50 at f/1.8, and the lens, camera, PEF EXIF, and JPEG EXIF all listed f/1.8.


  • 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, dslr, f/1.8, k100d, lens, photography
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Loss of aperture control on K100D teamgs Pentax DSLR Discussion 4 09-25-2010 01:00 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
using an aperture ring lens on the K100D Super burntsienna Pentax DSLR Discussion 3 02-25-2009 02:10 PM
For Sale - Sold: K100d with broken aperture control junkdon Sold Items 0 10-17-2008 03:45 AM

All times are GMT -7. The time now is 03:43 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]