The 135mm lens was popular because it was the longest length that could be used accurately on a rangefinder camera. In other words, the SLR inherited a strange focal length that has, IMHO, little to commend it. I find it too long for portraits, for example.

It's best not to reply to spam posts. It potentially makes them less easy to spot as more posts follow, and also encourages spammers to return as they are getting notifications of replies.

For consistency I use presets such as Daylight, Cloudy, etc. Then the camera records the light as I see it. AWB tries to alter the colour temperature to make am exposure that overall integrates to grey. So, for example, a red sunset becomes diluted.

There is also a custom setting that enables some variance even with the presets. This needs switching off if we don't want the camera to "correct" even a preset.

We do of course tend to hear about all the SDM failures, but recently there have not been so many and of course we don't hear about the ones that don't fail. I would ask SRS how many actually do get returned compared to sales and I'd suspect the answer may be very few.

The Pentax cameras had a certain elegance in design that was missing from Praktica and Zenit. Pentaxes also had wonderful viewfinders. And still do.

Zenitar 16mm might be a bit basic in its manufacture, but the glass could be good.

With fisheye lenses the usual relationship between focal length and field of view breaks down a bit. The improtant thing is to know whethr or not a lens is full frame (not in the format sense) or just a circle in the middle of the frame. Then, the field of view should be around 180 degrees. A few fisheyes can be 160 degrees and one is even 220 degrees (not Pentax).

The fisheye front converter is a cheap place to start just to see how it goes. It isn't the best quality though. The 10-17mm on an APS-C body is a fantastic lens. The 17-28mm is the full frame version, if you can find one. I see it's back in the lens roadmap, so hopefully eventually it will appear.

The newer lenses might use rear group focusing, or it could just be a new way of designing the internals of the lens. It does take a little getting used to, but in the end the important thing is that the zoom and focusing rings operate in the same direction for all lenses. That avoids confusion when using several lenses.

There's one sure way to find out - phone them on the number given. They are a reputable dealer so I'm sure they will explain the hows, whys and wherefores of the sale item.

I use a few film era lenses on the K-1, including the SMC Pentax-FA 50mm f/1.4, SMC Pentax-FA 43mm f/1.9 Limited, SMC Pentax-FA 20-35mm f/4 and SMC Pentax-FA J 75-300mm. All are fine.

The issue of the way the light falls on a sensor is real enough and modern lenses are designed appropriately. Having said that, it's more of an issue with wide angle lenses as the light at the edges of the images strikes the sensor at a much more oblique angle.