I am not sure how interesting this still is, but I feel I need to add my two cents to this one. There has been a lot of discussion on the Tamron adaptall-2 mount for Pentax. Not all of that was fully accurate. Some aspects are correctly described in Boz's Pentax pages as well. 1) There is an adaptall and adaptall-2 mount. I don't know how compatible they are. The below is refering to adaptall-2 2) As pointed out correctly there are two adapters done for Pentax: K and KA. They are easily to tell apart. The K features a small aperture scale for the finder read out in MX, LX and KX. The KA doesn't feature such a scale. I understand Tamron does not recommend the KA for non A bodies (e.g. ME, MX, ...). I asked that years ago on PDML. Users reported problems with a KA adaptall2 on MX. I have no first hand experience with the KA, since it was described as being a bit quirky by the time I asked, such that I got worried, it might hurt the camera. I use my Tamron lenses with a K adaptall-2 on my MZ-5n. 3) There are two types of Tamron lenses, some feature 22 as smallest aperture others 32. All lenses have one setting beyond 22. With the former it is AE only, with the latter a combined 32-AE setting. (On zoom lenses with variable aperture the 22 resp. 32 holds for the wide setting, at their longest setting these become higher numbers.) 4) How does it work: a) K adaptall: i) 22 lens: You can use all settings down to 22. You should avoid the AE setting. (It might be even blocked, I don't know since I don't own a 22 lens.) With this lenses Tamron doesn't give an aperture value the AE setting corresponds to (not calibrated). ii) 32 lens: You can set all apertures down to 32. The 32-AE setting works as 32 setting. The AE is not engaged in any way. b) KA adaptall: All lenses: In aperture priority you can set all apertures down to 22. The AE or combined 32-AE setting corresponds to the A setting on Pentax A, F and FA lenses. There is no way to set the 32 in aperture priority. The 32-AE works as only as A. 5) Slow lenses with KA: Because of the way, the KA mount is done, one can not have lenses with an aperture range 4.5 or slower until 22. This creates problems with the e.g. Tamron 300/5.6 zoom. The camera gets signalled a 4.0 lens. If it chooses apertures faster than 5.6 underexposure will result. This was detailed in the manual I got with a Minolta MD adaptall-2 (one manual for all adaptall-2) See Boz's page for detailed explanations: http://www.phred.org/pentax/k/FAQ/K-mount/Ka.html A 3.5-4.5 zoom lens is fine. It will be treated as a 3.5 lens. The system ignores the loss in speed towards the tele setting. I hope this lengthy write up is useful. Joachim - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
