[Greeneg]

I hope that this is the correct forum to post this question in, if it is not would the moderators please move it to the correct forum.

I have a K20D which I love. I recently acquired a Tamron Adaptall-2 500mm f8 which works very nicely with the K20D. I now have a Tamron Adaptall-2 2X
Flat Field Teleconverter. I notice that the latter has what appears to be an aperture control and blades which the f8 mirror lens does not. My question is as to whether or not the aperture blades in the converter can be used to stop down the mirror lens. I realize that the 2X effectively makes the mirror lens f16, but will the converter give me a little more range than I already have.

Thanks for you comments and suggestions.

[jeffkrol]

TC rarely have aperture blades. The Adaptall II may have the linkages (which in case of your mirror lens is unnecessary though).
Yes your lens will be an effective f16 and may not AF particularly well.
At 2x your lens will be a 1000mm lens.

[snostorm]

Hi Greeneg,

Jeff is correct that there are no blades in the TC.

The aperture markings on the dedicated Adaptall 2 2x TC are just offset 2 stops from the lens' markings to give an accurate display of effective Av with the TC in place, AFAIK.

It will certainly not give you any aperture options when used with the 500 CAT.

Scott

[Greeneg]

Thank you all, question answered.

[monochrome]

Thank you all, question answered.

Please note that the Tamron Model 01F 2X TC does not work with the 500mm mirror - Tamron made a special TC - the 200F (quite rare today, apparently) for a small number of long lenses

"
Tamron SP 2X Tele-Converter Model 01F: This 2X converter, compatible with most Adaptall-2 mount lenses, provides very good optical performance. The 6 element, 5 group optical design is housed in a moderately long barrel which is about twice the length of conventional 4 element 2X converters. The flat field optical design minimizes off-axis aberrations; spherical and chromatic aberrations are also extraordinarily well controlled. Tamron's literature states that this converter is designed for lenses with a focal length of 90mm and longer. Nevertheless this converter performs well with all Tamron zoom lenses which have a stationary master group (the rearmost group of lens elements). This converter can also be used with many Tamron wide to tele zoom lenses for doubling macro magnification, and usually results in better off-axis macro performance.


Note that Tamron also produced the very rare SP 2X Tele-Converter Model 200F. The 200F converter was designed to be used with Tamron's SP 300mm F/2.8, SP 400mm F/4, SP 200-500 F/5.6, and the SP 350mm F/5.6 and SP 500mm F/8 mirror lenses. The 200F converter can not be used most other Tamron lenses since the converter's front element will come in contact with the lens's rearmost element when you try to attach the converter."


Tamron SP Adaptall-2 2X Tele-Converter Model 01F

Moved to Lens forum.

@Greeneg, if you're not sure whether you've got the right forum in future, post in 'Everything Else' please.