Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-15-2008, 08:32 AM   #1
Veteran Member
ftpaddict's Avatar

Join Date: Jan 2008
Location: Yurp
Photos: Gallery
Posts: 4,669
How do A lenses report aperture?

Question Question.

Unless they have some sort of electronic doohickey inside that tells the camera its maximum aperture, how does a camera body know when a lens is 1.4 and when another one is 3.5?

05-15-2008, 08:42 AM   #2
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,352
I think the best resourse is here

Pentax Lens Modifications for Matrix Metering - Mark Roberts Photography

In principle, when you look at the camera body contacts, there is one recessed pin. (third pin from the lens locking pin I believe) If this pin is shorted to the lens mount then the camera thinks it is an A lens.

That is the reason this pin is recessed, it requires the presence of a corresponding pin on the lens to activate the apature sensing. Normally it will not contact the lens mount when a non A lens is mounted. The remaining 5 pins on the A mount tell the camera the maximum and minimum apatures

Last edited by Lowell Goudge; 05-15-2008 at 09:02 AM.
05-15-2008, 08:47 AM   #3
Banned




Join Date: Oct 2007
Location: Savannah, U.S./Baguio City, P.H.
Posts: 5,979
Im pretty sure this is correct, though maybe not so useful.

with A series lenses six electrical contacts are added to the bayonet ring. One is slightly recessed and allows the lens to indicate whether the aperture ring is set at 'A' or not. If it is, a pin on the lens extends slightly and makes contact, while if the lens is at any other setting the pin is retracted and does not make contact. The other five contacts are used to encode the lens' aperture range. Each contact on the lens is either conducting or non-conducting, providing a binary 1 or 0, respectively. Two contacts encode the lens' minimum aperture—f/16, f/22, f/32 or f/45; although no Pentax K-mount lens has ever had an f/16 minimum aperture. The other three contacts encode the lens' maximum aperture; their meaning is dependent on the minimum aperture indicated by the lens.

yep the link provided by Lowell Goudge tells the same thing but with pictures and diagrams! so yea the link should explain it all. and much much more about pentax lenses.

Last edited by séamuis; 05-15-2008 at 09:11 AM.
05-15-2008, 09:00 AM   #4
Veteran Member
ftpaddict's Avatar

Join Date: Jan 2008
Location: Yurp
Photos: Gallery
Posts: 4,669
Original Poster
Thank you, everyone. That pretty much clears everything up.

I was feeling a bit like this guy here > because I used some gear I did not know the exact working principles of.

Reply

Bookmarks
  • 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!
camera, k-mount, pentax lens, question, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fixed-aperture lenses Adam Pentax SLR Lens Discussion 4 05-29-2010 10:26 PM
MZ-S and aperture-ring less lenses Gooshin Pentax Film SLR Discussion 10 01-11-2009 12:28 PM
Aperture, Old Lenses and werewolves marlon Pentax SLR Lens Discussion 2 10-10-2008 11:47 AM
Aperture ring on FA lenses ankit Pentax DSLR Discussion 8 02-04-2008 04:54 AM
M lenses - no aperture control? dugrant153 Pentax SLR Lens Discussion 1 11-20-2007 01:31 AM



All times are GMT -7. The time now is 04:12 AM. | See also: NikonForums.com, CanonForums.com 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?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top