Lens mount query

Could someone please explain the following mount details - Sigma 75-300mm F4-5.6 DL AF lens; PA-Z pentax mount. Thanks...

I think the PA Z refers to power zoom lenses that were released in the 1980's and 1990's, these had a powered zoom feature. Lenses with Power zoom are compatible with the current K mount on digital SLR's but the power zoom feature will not work (not that this is a disadvantage anyway).

Regards
David

PA-Z might reference to PK-AF2 rather than PK-AF (SF series) - I gather the change to AF2 enabled some features absent from the original AF mount

The Pentax FA Power Zoom lenses had the K-AF2 mount (screw-drive AF mount with Power Zoom [now the SDM/DC] contacts). The Pentax PZ lenses will power zoom on my K-5, but they don't use the 'zoom clip/burst' modes that the Z series film SLRs offered.

As for Sigma lenses - anything's possible, it could be a lens with power zoom, or just a screw-drive AF lens. 'PA-Z' was not a Pentax designation so this is likely Sigma's own name for a Pentax AF mount produced around the time of the Z-series SLRs (early-mid'90s).

I thought the Pentax power zoom designation was FAJ? And if you have one that doesn't work on (powerzoom bit of it) on a modern body can the drive motor be disengaged to allow manual movement with the focus ring? I'm wondering if this makes it too loose ...?

The FAJ lenses were the first ones made without aperture rings and released for use with the *ist film body. The 18-35mm (full frame) was also the standard lens for the first DSLR in the way we know them now, the *istD.

The Power Zoom lenses were FA lenses.

Thanks John, do the powerzoom FA lenses have any specific extra letters to indicate the powerzoom feature?

As I recall, they are just marked "Power Zoom" - there are quite a few of them. It was clever, but never really caught on despite the neat tricks that could be done.

The contacts can now be used for SDM lenses, but still enable power zoom lenses to be zoomed using their motor.

It's expected now on bridge and compact cameras, but power zoom on SLRs was probably ahead of its time.

IIRC all the first FA zooms were PZ lenses (28-80, 28-105 & 100-300) to compliment the PZ features of the Z-1 & Z-10. It was only later that FA zooms were available without the PZ functionality.

The lenses are just marked 'FA' but with 'Power Zoom' visible on the top when in PZ mode. The zoom collar clicked forward/back to switch between PZ & manual zoom mode. There was also an additional switch and button (marked 'PA>ZS') to activate the zoom clip, zoom memory & zoom during exposure offered by the Z series.

The PZ works at 3 speeds depending how far you rotated the zoom collar. In manual zoom mode, it feels a bit rough compared to a manual zoom but is fully usable on any PK camera (assuming FA lenses). The basic PZ functionality works on my K-5 and I guess on any camera with the SDM contacts, the Z series zoom modes only work on those bodies. When you turn the camera off, the lens zooms to it's smallest physical length. Apart from being slightly heavier, they work perfectly fine on any PK camera.

It was of limited use, especially given that it drained (the then expensive) lithium non-rechargeable battery (2CR5) quickly. With current batteries this would be negligible. The consistent speed of the zoom might work well for video apart from the noise if using an on-camera microphone.

The Z series zoom modes can be summarised as:
- Zoom clip: set 1 or 2 focal lengths and select at the press of a button.
- zoom burst: zoom during exposure (longish exposures).
- auto zoom: Set a subject magnification and it would zoom to compensate if the distance changed.
- portrait mode: pick head & shoulders or full length and it would zoom according to the subject distance.

John.

Many thanks for that great informative post. I'd love to meet one if these zooms one day, but guess they are a rare breed now.

The lenses are usually available but you have to know what you're looking at. A lot of sellers don't realise it's a PZ lens as the zoom collar clicking isn't too intuitive. The 'PA>AS' switch cover is a weak point and many (most?) have probably broken by now and are usually taped up (it doesn't affect operation on non-Z series cameras).