The Pentax will be 200mm (or should be as it's a prime). The Sigma is noticeably shorter than 200mm at close focus, though it will be a true 200mm at infinity.

If you watch Tony Northrup's you tube channel you will know he often mentions the issue of focus breathing, particularly with 70-200 lenses at closer distances.

Having just bought a DA 200mm prime I thought I would compare it with the Sigma 70-200 at 200mm. Both shots at f2.8 from the same shooting position about 9 feet from the subject.

This from the DA 200mm



This from the Sigma at 200mm



A significant difference, as you can see.
edit: I don't know why these are sideways but they still illustrate the point

Could you give me a bit more explanation please Peter? I have been looking closely at the Scotsman picture and it looks fine to me. Are you saying that the whole thing is out of focus or that it is not focused on the right part of the image?

Thanks Brian. That's exactly what I wanted to find out. I was aware that the 1.4x is officially APS-C but in practice it looks to be useable on FF. A bit of 'vignette correction' should do the job, I would think. Or a fairly modest crop.

I have ordered a Pentax DA 200mm f2.8 (I blame David Trout who always produces such great images from his). At some point I may want to pair this with a 1.4x converter. Will this combination give me FF coverage?

I was watching a K1 review on you tube last night. They were using a Sigma lens on it and the scratch on the housing was clearly visible, although they did not remark on it.

See my post a bit further up this thread. The bit of red tape I put on the camera shows where the mark is (I have since replaced the red tape with black to make it less noticeable).

I just tried pixel shift for the first time to see if I could tell the difference. These were taken on a tripod, so no motion correction. I took 2 shots - one with pixel shift, one without.

Here is the whole image



Here is a crop of the centre - no pixel shift



Centre crop with pixel shift



So, yes there is a discernible difference, although you have to peer very closely to see it.

Yes. I have the non HSM version of the 24-70. It is a comfortable fit - no rubbing - and performs very well on the K1

It would be a lot trickier to put the tape on the lens because it would have to cover the arc between entry point and locking point, so a longish and extremely narrow strip of tape would be needed. Might be possible though.