Is my teleconverter defective?

Started Nov 8, 2013 | Questions thread
brandrx Forum Pro • Posts: 28,337
Re: Is my teleconverter defective?

GossCTP wrote:

My Vivitar Series 1 1.4x TC was waiting in the mailbox when I came in this evening. I was playing around with it, but I noticed that it was reporting the full aperture of the lens. As in, I could still get f/1.4 on my FA 50, even though it should only be f/2. It says the focal length is 50mm as well. Perhaps that's why the instructions say to turn off SR. I haven't had time to play with it in decent light to see if it's underexposing The body is a K20d. Is this normal?

P.S. - I didn't buy it to use on the 50. It behaves the same on the A* 300 as well.

That is normal. All autofocus teleconverters that are for Pentax mounts do not pass any corrected focal lengths or apertures to the camera. The one exception is the Pentax-F 1.7X AF Adapter will pass the corrected aperture but not the corrected focal length to the camera.

So, for the Pentax-F*300nn f4.5 + the Vivitar 1.4X attached you will read 300mm and wide open of f4.5 at the camera. The exposure will be correct though as if you had a 420mm f6.3 lens attached.

EDIT: Note that you will still have SR capabilities but it will be somwhat less. For instance an F*300/4 lens will have SR for 300mm instead of 420mm.

Note 2: With that teleconverter attached to the A*300/4 and if you have SR turned on the it will ask for you to enter the focal length. Enter 400mm.


-- hide signature --

Ron - 'We don't have time to go take pics this afternoon Carl.'
Carl - 'What do you mean? It will only take 1/1000s.'
'Keep your eyes looking forward. However, glance back now and then to see where you've come from. It will put a smile on your face.' ~ brandrx

selected answer This post was selected as the answer by the original poster.
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow