I just spent $50 for Sigma's original 'impossible' wide-angle zoom, the 21-35mm f/3.5-4.2. This one was made around 1980 and was the very first wide-angle zoom of any sort it seems; the answer was to make two sets of elements shift in the zooming process. It seems they did it so well that they made it several times in manual-focus alone, before moving the design to AF in the mid-80s - it comes labeled as Sigma Zoom, then Gamma and later Gamma-II. All copies have the PK-A aperture connection for Pentax (odd, was the A setting in play that early?), some have infinity at the far left of the focus ring and others at the far right. The one I acquired has no Gamma marking and focuses like a true Pentax lens. Also this copy is a 1-touch focus/zoom (others have two rings) and the hood is attached permanently to this one unlike some others. Crazy!
Did I mention it's a FFFF (full-frame/film friendly) lens? Guess not...
Anyway, this could be an ideal video lens with enough depth of field to just set to 12 feet and f/5.6 and ignore that issue. I spoke of a 28-105 as a great video lens before, but that much zoom was too much and it needed to go wider on the aps-c platform - so this feels like a better fit. It weighs about a pound though so we'll see if it will do. What few reviews I've found online from owners speak well of it, but with so many variations it's hard to say if every variant is spoken for. The pentaxforums site shows the lens but it has no reviews; that says a lot for its rarity!
