Originally posted by Nimrad I just received my Pentax FA* 80-200mm (man what an amazing lens!), and I noticed some buttons on the side. There is one button and there's a sliding switch. The switch is a switch between PZ, AZ and Mode. What the hell does this mean? :P
I have both the FA*28-70 f2.8 and the FA*80-200 f2.8 and yes, they are amazing lenses!
The FA* zooms were equiped with a motor that drives the zoom, so that you had the feature of power zooming, like in a P&S camera. The zoom speed is controlled by the amount you turn the zoom ring *when the power zoom is engaged*. To engage the power zoom feature, you need to slide the focus ring forward or backward depending on the mode you require, i.e. power zoom or manual zoom.
The power is derived from the contacts inside the lens mount and you can see them when you take the lens off, both on the camera and the lens. I actually like the power zoom system, but some others don't for some reason. The reason I do like it is because in the power zoom mode you only need to turn the zoom ring a small amount instead of twisting your hand around the lens, if in the manual zoom mode, like normal manual zooms. In manual zooms, the action of needing to twist the zoom ring through a large throw means that you sometimes can misplace the subject matter through bumping the lens whilst zooming. With the power zoom, it is a matter of gently turning the zoom ring a small degree and thus preserving the subject matter in the VF.
The power zoom works in three stages, slow medium and fast, by turning the zoom ring a small amount, a medium amount or a larger amount. Even turning it a 'large' amount is still only a small throw when compared to manually zooming.
The buttons and sliding switches on the FA* zooms were used on the Pentax film cameras for things like Zoom Clip and Image Size Tracking. I can't remember the exact way they worked, but I think the Image Size Tracking would keep the subject at the same size throughout your panning and would only allow shutter tripping at the appropriate and approximate subject image size. Zoom clip would automatically zoom to the predetermined subject size and then allow the shutter release, or some such thing. As I say I can't remember the exact details as I never used these features and I thought they were a bit of a gimmick, but they are irrelevent as they do not work on the DSLR's.