I would suggest looking at 55-77 on a dslr. The underrated K55 f/1.8 can do a nice portrait, my favourite is the 77 Limited, which may be too long for you. Still in the Pentax world alone we have the following to choose from, K55 f/1.8, DA*55 f/1.4, DA70 f/2.4 Limited & FA77 f/1.8 Limited covering a range from 82.5 to 115.5 in 35mm terms. I wonder if the 100 might be a bit unflattering due to its inherent sharpness?

What time lapse from the first shot to the last on your original set? A grey sky as a target?
I would need a controlled target and lighting to bother to even attempt this 'test'. Won't happen in the next few days or month perhaps, but I will get around to doing this.

Can you give me the test process please so I can try it myself? I wonder how a manufacturer programs the output of a sensor if it does not have any aperture info to work from when using an all manual lens such a K series?

I don't quite understand this, are you talking about the AF sensor and not the actual sensor itself?

The AF module is not affected by a different focussing screen. It does have an impact on spot metering though.

Fitted perfectly out of the box. Just like my last one on the K20D. 2 min job.

I doubt they would make a (D)FA version of the 50 f/1.2, the current AF module would struggle too much I think. They do however still sell new A series versions on the Japanese market , would make a nice bundle.
With regards Katzeye, I ordered on a Friday night and received 9 days later. Just under £150 all in.

I just copied the jpegs to smugmug. No pp with the exception of a crop on No:3. They are smaller versions though, the original size is sharp enough for me.
Smugmug Link if you wish to view full sized versions.

No affect whatsoever on AF with the Katzeye, it does however give you an extra option to double check the AF accuracy if needed. I got the version with Optibrite and the std Pentax AF markings. It is brighter screen than the one supplied with the K-5 which I think Amateur Photographer complained about. They would not complain with the view i'm getting. I have not taken the 50 off since I installed the Katzeye, must be the best value available light combo going.
I concur with Womble's idea that Pentax should offer a OE fit focussing screen with split prism, they could sell it with a new Limited A50 f/1.2.

Thanks for your comments, appreciated.
Well No:1 is a bit at the limit I suppose, checking the exif on smugmug its reporting iso80, 1/8000s Pure operator error. Should have stopped down but I was in a Katzeye play/test mode. I'll have a look at the raw file tomorrow and see what I can pull back.