A Pentax-M 35mm f2.0 looking for a new home - it doesn't get much use as I also have a 30mm f2.8.
Price £120 ono (inclusive of P&P in the UK). Happy to post overseas.
I've used this on a *ist DS with no problems. Optics and aperture blades are clean and the focusing & aperture rings show only minor signs of use.

Well regarded - for user reviews see:
link

Bump
Price reduced to £35 for the Pentax-M 50mm f1.7

Rechecked the 55mm and found the trace of fungus to be on the surface of the lens - now cleaned.

SMC Pentax-M 50mm f1.7
Replacement front cap and original rear cap.
Clean optics and snappy aperture, minimal signs of wear on the focusing and aperture rings. £40 (incl P&p within the UK).

SMC pentax K 55mm f1.8
Replacement front cap and original rear cap.
Slight touch of fungus visible on the edge of the front element (just above the I of ASAHI in the photo) which doesn't affect the picture quality - I've exposed the lens for several hours to a UV light which should have stopped any further spread. Otherwise clean with snappy aperture and minimal wear visible on the focus and aperture rings.
£40 (incl P&p within the UK).

Both lenses have been used on a *istDS and show no problems over a range of apertures.

Prepared to post overseas but will need to quote for postage.

Pentax-M 50mm f1.7:





For user reviews see: link

Pentax K 55mm f1.8:





For user reviews see: link

Hi, still no joy after cleaning the contacts .
Regards

Hi, I recently purchased second hand a DA 50-200mm. Using this on a *ist DS I find that (in Av mode) the aperture is not displayed and the autofocus doesn't work - anyone else with experience of this? Unless there's a fairly straightforward fix I'll have to return it.

Focusing with the Revuenon 55/1.2 wide open appears to be a little tricky due to the very narrow DOF. I've ordered one of the Chinese split prism screens off ebay - hopefully this will make manual focusing easier on my *ist DS, although I've read there may be problems with the screen becoming too dark at low apertures.

The Revuenon MC 55/1.2 K doesn't have an f1.4 setting - it goes f1.2 then f2. With a 58mm filter ring and 9 aperture blades I believe it has a different design to the Porst 55/1.2 (55mm filter ring).

I recently acquired one of these and will be comparing with a S-M-C Tak 55/1.8, K 55/1.8, S-M-C Tak 50/1.4 and an A 50/1.4.
Anyone else with any experience with this lens? - I believe the construction is simimilar to the M42 55/1.2 Tomioka's from the 1970's but made by Cosina in the early 1990's.
Here's a few examples of the Revuenon 55/1.2 shot wide open:
link

I found this info about a DIY Soft Focus Lens (not specifically for a Pentax DSLR) which is aimed at replicating the behaviour of the Rodenstock Imagon Medium/Large format soft focus lens:
link

I'd be interested to hear of any experience with the lensbaby soft focus system.