The SP series of the Adaptall lenses were premium lenses that were better build and usually optically better than the regular non-SP series. I was, and still am, a big fan of Adaptall lenses. Still have a dozen of them, and among them is the SP 60-300mm f3.8-5.4. It's a very large, long, and heavy lens. With the hood, and fully zoomed out, it could look intimidating. Many dismiss this lens due its slow maximum aperture at the long end, but with today's digital cameras, this shouldn't even be a concern, but when using long end at 300mm, it's not easy to keep the image from jumping in the viewfinder, and thus hard to focus. Cameras like the OM-D E-M5 or E-M1 are better for this focal length, but using a zoom lens with In-Body-Image-Stabilization is too cumbersome as you will have to change the focal length in the camera when you change zoom position.
I find the lens very good optically, even when used at full aperture. There is the unavoidable colour fringing at larger apertures, but it's not unique to this lens. Besides, it takes a few clicks to fix in Lightroom. Even after decades, the zoom is still very smooth and no severe zoom-creep. I think it's a good value for range and its optically competent. A good choice if you need long reach and reasonable cost but with good image quality.
Mohawk helmet - Tamron SP 60-300mm f3.8-5.4 & Sony A7. click for larger.
Three Amigos - Tamron SP 60-300mm f3.8-5.4 & Sony A7. click for larger.
One legged seagull - Tamron SP 60-300mm f3.8-5.4 & Sony A7. click for larger.