[j blair]

I would really like a long lens for wildlife shots in the (Arizona) desert. While lusting for one of the Sigma 50-500mm units I purchased a Vivitar 1.4 teleconverter to use with my Sigma 70-300 lens.

Doesn't work very well. I noted when I mounted the TC and Sigma lens the screen on the K-30 started to flash. I knew I would have to go manual but even when set on M the flashing persisted.

I thought that outside I would have enough light for the autofocus to function. Nope. I was able to get a few decent pictures but with my (high mileage) eyesight and the shallow depth of field, more were blurs than crisp.

Any guidance? I thought maybe there might be a 250 or 300 mm prime lens that might allow the autofocus to work. But haven't found one yet.

(Plan B is to sell the TC, sell one of my other lenses and hope a bargain comes along on a 400-500 mm lens.)

jmb

[jatrax]

Any guidance? I thought maybe there might be a 250 or 300 mm prime lens that might allow the autofocus to work. But haven't found one yet.

300mm f/4 should work in decent light. But by the time you buy one of those plus the TC you are in the 50-500mm price range again. Unless you can go manual focus, in which case you can get an older 300mm f/4 for not ridiculous money. I have used an S-M-C Takumar 300mm f/4 with a TC. Image quality is OK but lots of CA. And you need really good light.

You don't mention which TC you bought (and there are many different ones that look similar) but if it is a manual one then did you turn on "Use Aperture Ring" in the camera settings? If you did not that can cause the aperture indicator to blink "F---".

[vonBaloney]

Is that an HSM lens? I have a Vivitar 2x TC that is a few years old -- it has SDM contacts on the body side, but not the lens side. When I tried to use it with my Sigma 8-16 HSM lens (just to see what would happen), the camera went wonky -- screen flashing as you describe, etc. Even if I set it to manual focus, it just wouldn't operate at all. So I would say don't even mount an SDM/HSM lens on a TC like that. That's the only SDM/HSM lens I have -- it works fine on normal screw-drive AF lenses.