The characteristics of the K series lens are likely to be adifferent from the M and A series. The latter two should be the same.

The original K lenses were mostly bayonet versions of the SMC Takumar screw thread lenses. These would exhibit maximum resolution around f/8 - f/11, where quality could be quite staggering. Wide open they will show sharpness but the reproduction will be softer.

The M and A series follow a new trend of wanting better wide open performance, sometimes at the expense of slightly lower optimum resolution. The peak of the performance will also be reached earlier, perhaps f/4 - f/5.6. These may also show higher contrast.

Hope that helps!

Technically, the 77mm is slightly better, bit I too preferred the 70mm. It has a certain undefinable quality.

The 70mm is a beautiful lens. If you don't need macro, then it would be very hard to better.

To be fair, I'll bet you've learned a bit about photography since the 1980s, when you must have been in your teens. The Pentax 67 and the Pentax 35mm SLRs all work in similar ways. Manual cameras will never be the fastest way to do street photography, unless you preset the distance and exposure and just shoot. This might well work, but with apertures of f/1.4 the focusing would be a bit critical. Try f/8 (marked in red on the aperture scale) and set the distance in the same way, there's a red setting.

This "snapshot" setting is available on many Pentax wide angle manual focus lenses.

As the trail had gone cold I have now set a new competition, so hope you have enough time to respond!

Judges, please be prepared to judge if you win. Winners, please be prepared to set the new competition promptly. We have had a good run lately, so let's keep up the momentum!

You've got a fair point there RobL, no point in pining over exotic lenses that we could never afford. The new Pentax 15-450mm is expensive enough and pretty much at the limit of what we could spend on any lens.

Maybe times are tough for Sigma along with everybody else, so choice suffers.

The Pentax 150-450mm seems to me to be the lens you may need, so why not wait a few months for its price to ease and see where you are then.

Alternatively, snap up a Pentax fit lens while you can. I don't see the point in wasting money changing systems, because it will only bring up new and different problems from the ones you may perceive now.

I check the monthly entries through the month, usually once a few have built up.

Indeed, if I don't hear anything back by early evening a new competition will be posted anyway.

All of these show a slight lack in vitality and i think this is because you have gone a little too far in avoiding blowing out the yellows. Yellow is a brilliant, vital colour, not dull. It's a tricky thing to get right.

I would have liked to see more depth of field in the close ups, again not easy, but carefully focusing on the hyperfocal distance and using the smallest aperture possible should do the trick.

Hope that helps, because the basic idea is right and it just needs honing a little more.