Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
06-06-2011, 12:18 PM   #1
Veteran Member




Join Date: Jan 2010
Location: Durham, nc
Photos: Albums
Posts: 887
Tricking Kx into thinking manual lens is A-lens

I have a 500mm f/8 mirror lens. I want the camera to think it's an A lens set to f8 so that PTTL flash will work. Specifically, I want my Sigma 610 flash to work in PTTL high-speed sync mode with this lens. Is this possible?

Charles.

06-07-2011, 06:02 PM   #2
Veteran Member
selar's Avatar

Join Date: Jul 2007
Location: Sydney, Australia
Photos: Gallery | Albums
Posts: 2,035
Try shorting the lens contacts using aluminium foil or tape.
06-07-2011, 06:28 PM   #3
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,314
QuoteOriginally posted by ChopperCharles Quote
I have a 500mm f/8 mirror lens. I want the camera to think it's an A lens set to f8 so that PTTL flash will work. Specifically, I want my Sigma 610 flash to work in PTTL high-speed sync mode with this lens. Is this possible?

Charles.
with a mirror yes, it is possible

you need to look at the pentax pin assignment for max and min aperture and work out the coding for your lens, use nail polish to insulate the necessary pins. then, for th epin 3 location you need to get a spring loaded pin, I used a pin from a grid array IC socket, which was spring loaded, and inserted it into a mount to give the A contact (3rd location from the locking pin, and the only recessed pin on the camera)
06-07-2011, 07:17 PM   #4
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
QuoteOriginally posted by Lowell Goudge Quote
with a mirror yes, it is possible

you need to look at the pentax pin assignment for max and min aperture and work out the coding for your lens, use nail polish to insulate the necessary pins. then, for th epin 3 location you need to get a spring loaded pin, I used a pin from a grid array IC socket, which was spring loaded, and inserted it into a mount to give the A contact (3rd location from the locking pin, and the only recessed pin on the camera)
Lowell,

I found small spring ball plungers on mcmaster.com http://www.mcmaster.com/#spring-plungers/=cngn39

How does one easily lay out exactly where to put it on the lens base?


Last edited by newarts; 06-07-2011 at 07:32 PM.
06-07-2011, 07:40 PM   #5
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
QuoteOriginally posted by selar Quote
Try shorting the lens contacts using aluminium foil or tape.
That's quite difficult to do in my experience because the A pin is recessed. I have heard of people who have managed to trap a small ball of tinfoil - but I've never been successful.

It is easy to modify the camera mount so it thinks that all lenses are A type by short-circuiting the mount's A pin as follows:


I've not found a downside to this mod & it is easy to reverse should a downside appear. It is not a dangerous nor difficult procedure.

The major benefit is that P-TTL works for all lenses.
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!
flash, k-mount, lens, pentax lens, pttl, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Thinking about a new lens, would love some input. chrisb3 Pentax SLR Lens Discussion 9 05-25-2011 11:54 AM
lens question - manual lens won't fire wackymummy Troubleshooting and Beginner Help 7 05-21-2010 10:16 AM
Thinking on a new Macro lens. Advice? Ouroboros Pentax SLR Lens Discussion 15 04-15-2010 05:04 PM
Thinking of getting a new lens...what's your favorite? timstone Pentax SLR Lens Discussion 28 03-28-2010 01:05 AM
Kinda sorta thinking of a new lens... sebberry Pentax SLR Lens Discussion 10 08-04-2009 06:32 AM



All times are GMT -7. The time now is 05:52 AM. | See also: NikonForums.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