Lenses with Aperture rings

I have a question regarding lenses with aperture rings. I have an old vivitar 80-200mm zoom lens with a 2x teleconverter, which when used in manual mode on my pentax ist DL2 can get reasonably decent results when shutter speed set by rotary wheel on the camera and the aperture via the ring on the lens.

However when I try and use a newer sigma 55-200 lens which does not have an aperture ring. The results are much too dark.

I would like to upgrade to 70-300 mm lens and use the teleconverter as funds wont stretch to sigma 50-500.

Any solutions would be welcome

For a budget telephoto, I recommend the Tamron AF 70-300mm LD Di. It happens to have an aperture ring, but you don't need to use it to get decent results.

Selecting the aperture via the camera should give exactly the same result as using the ring. I think there may be something funny about your Vivitar if you get different effects with that with the different methods. And the Sigma being too dark is probably nothing to do with the lack of aperture ring. The camera just does expose differently with different lenses sometimes. Compensation is required then.

Martin,

Welcome to the best forum in the world!

(But you already knew that didn't you?)

Just a thought but are you using the newer Sigma with the teleconvertor? If there's no aperture ring on the lens, and the camera can't talk to the lens because the T/C is inbetween them, then the lens will be stuck at its smallest aperture at all times (normally f22 or f32 or thereabouts) which would account for severely underexposed images.

Sounds very plausible - if the T/C is manual.

Yes the teleconverter is manual - 1980s vintage from when I bought my original ME super

I guess I may be better off with an older 2nd hand lens

The Tamron I mentioned has a traditional aperture ring, so can be used in the same way that you would use an old Pentax lens.

Another alternative would be an auto converter - auto-exposure or even auto-exposure and auto-focus. The fully auto Kenko 1.5X I have works reasonably well with the Tamron 70-300.

That or a newer teleconverter with automatic pass-through.

I have a 7 element teleplus auto converter which cost me about £30 on fleabay, they aren't necessarily expensive.

Had a stroke of luck in a round-about way. My teleconverter broke on Sunday ( some screws came loose ). Took it to local camera shop on way to work today. They fixed the converter and as luck would have it also had a 2nd hand Tamron 70-300 as recommended by (iceblinker/Pete) for £65.

Many thanks for all the replies.