Tamron 28-70mm F/3.5-4.5 Model 44A: Autofocus camera bodies and their accompanying autofocus lenses had already become all the rage when Tamron's 28-70 model 44A and the 70-210 model 46A lenses were introduced in 1986. Tamron correctly anticipated that sales of these two manual focus lenses would be moderate, and designed these two lenses to be as cost effective possible to manufacture. This lens, like its telephoto zoom sibling, incorporates high strength plastic instead of metal wherever possible. The focus and zoom collars are made of plastic and feature integral knurled plastic grips.
While both lenses looked and felt a bit cheap, there was no compromise in optical performance since Tamron wasn't willing to sacrifice optical quality in the pursuit of additional cost saving measures. Overall optical performance is somewhat above average and yields good to very good results at F/5.6 and smaller apertures. Optimal aperture is F/8 or F/11 depending on the zoom setting. The 28-70's optical design borrows heavily from the SP 35-80 F/2.8-3.8 and incorporates the same basic features. Like the SP 35-80, this lens features a maximum macro magnification at the telephoto focal length and incorporates the Minimum Object Distance (M.O.D.) selector system whereby turning the focus ring to the minimum focus distance causes the zoom ring to automatically move to the telephoto position. This lens, as with the SP 35-80, has a slight excess of barrel distortion between the wide angle to normal zoom range.