Originally posted by oeriies In order to have shake reduction work correctly, I want to tape the electrical contacts on one or more of my TCs so that I have to manually enter the focal length of the lens rather than having the TC passively transmit the focal length of the attached lens. I want all other functions to be unchanged. Which contact or contacts do I tape over?
My specifics are a K-5 and a Sigma 500mm f/4.5 lens coupled with the Sigma 1.4, or Sigma 2.0, or Tamron 1.4 teleconverter. I want the camera to think that this combination is a 750mm lens rather than what it now thinks, which is that it is dealing with a 500mm lens. If there is a way to accomplish this through a software hack that would be great, but any solution would be welcomed.
Russ
Thanks to everyone for the replies. I followed up and here is what I found: a) Based on the EXIF data every teleconverter I own except the Pentax-F 1.7 passes the lens information from the attached lens to the camera unmodified. Thus for the two Sigma TCs and the Tamron (and I expect for every other TC out there except the 1.7) a lens of a particular focal length, e.g., 500mm, is seen by the camera as a 500mm lens regardless of the attached TC. b) Taping over the data contact pin allows manual setting of the lens focal length but autofocus is lost. c) Attaching the TC to the camera before a lens is attached and turning the camera on allows manual setting of the focal length, but when the lens is attached the camera defaults back to the actual lens focal length, e.g., the manual setting of 700mm defaults back to 500mm for a 500mm lens.
This means that for a modern lens with a TC attached in-camera shake reduction on a Pentax body will always be working with the wrong input value for lens length unless the data contact pin is taped over, in which case the lens becomes a manual lens, or the TC is the Pentax 1.7, which in effect also turns a modern lens into a manual lens.
This is something Pentax could and should fix through software by allowing an option of manual override of the lens length value on a lens-by-lens, just as it currently allows a microfocus adjustment on a lens-by-lens basis. Thus for my 500mm lens, which is the only one to which I attach at TC, I could set a custom function that always requires me to set a manual focal length when I attach that lens. Alternatively, if Pentax every gets around to making a modern TC it could build electronics into it that transmit the correct lens length.
I don't know how much of problem the wrong lens length value creates for shake reduction. I never turn shake reduction off and manage to get acceptably sharp images using a 1.4 TC, but I'm always shooting from a tripod when I'm using a TC so maybe there's no shake for the shake reduction system to reduce.
Russ