Tamron SP 90mm f/2.5 Macro (52B)
This is without doubt my favourite Tamron Adaptall 2 lens. In fact it's one of my favourite lenses of any type on both film cameras and digital. It's definitely worth looking out for. I would suggest going for the earliest 52B variant, though that is mostly for cosmetic reasons: it's is just a very distinctive and, IMHO, beautiful lens.
As is usual for Tamron Adaptall 2 fixed focal length lenses the maximum aperture is f/2.5 rather than the f/2.8 of most competing lenses. Not a big difference, but still a nice little bonus if shallow depth-of-field is your thing. This also makes it very suitable as a portrait lens. One disadvantage of this lens, at least in comparison to modern macro lenses, is that the maximum reproduction ratio is 1:2 (i.e. half life size) instead of 1:1 (i.e. full life size). But that is common amongst vintage macro lenses, and a matched extension tube and a matched 2x teleconverter give you two ways to achieve a 1:1 reproduction ratio. So if that is important to you these accessories are worth looking out for.
Photographs taken with the Tamron SP 90mm f/2.5 Macro lens
The first 4 photographs were all shot using a Pentax ME Super on Kodak Portra 160. The location is the lovely Dr. Neil's Garden here in Edinburgh.
The next 8 photographs were all shot on either a Pentax K-7 or K-3ii DSLR using the Tamron Pentax K-A mount which has the electronic contacts necessary for full access to all exposure and metering modes. The B&W ones were processed using Nik Collection Silver Efex Pro 2.
Tamron SP 90mm f/2.5 Macro (52B) on the adaptall-2.com website