Tamron SP 24/2.5 adaptall II

This old lens uses the adaptall lens from Tamron can be used on almost any brand of camera with the right adapter. This is a unique thing and this adapter even gives the f-number to the body making full-open metering possible. On a digital Pentax you need stop-down metering with the green button, but is not the fault of this lens. At the time of release a 24mm was very wide and 15mm was even extreme (like 10mm on a crop).
This lens feels very solid and has been used very often by my dad (like you can see). Because of the nature of wide angle focal length I never missed AF, also because it's not a zoom lens, so you need the time to put it on the camera. As a point and shoot lens on a digital body, you could put it at f8 and focus at 3m and everything is sharp from about 1.5m to infinity. How needs AF? On a digital body it becomes a 35mm and this is my favorite length for overall photo's giving a very natural look to a picture.

Performance
Wide open this lens is as bad as the FA50/1.4 at f1.4, but this lens is 2 stops slower. f4 only makes the corner a bit sharper. This lens needs f5.6 to become good. At f11 it's very good and also great for a maximal dof. Comparing to my other MF lenses it can't compete. But when comparing to a M28/2.8 it's not so much worse. This lens has some very light scratches on the very small back element making this results worse then some other samples. This lens also has a good thing that is CA or better the lack of CA. This is very uncommon for a wide angle lens especially at that time. Maybe the Tamron coating better then most people think. I've always readen that the Pentax coating is top, but most re-badged Pentax lenses made by Tamron perform better from Tamron...hmmm But CA is only one aspect, this lens does suffer more from direct sunlight then the Pentax lenses and I don't have a lenshood for it. This lens also uses a uncommon 55mm lens-tread. The contrast is lower then avarage (I've given it a 8)

So what is it good for.You can use it on any brand you own, feels solid. They sell very cheap, but it's difficult to find a decent sample. I would rate mine BGN- and a when I look at the results from "Chasseur d'Image" the center resolution could be much better. If you are looking for a 35mm equivalent lens and don't want to spend money on the excellent and expensive FA24/2, DA21/3.2 or rare A24/2.8 then this lens is a option.