It is absolute fact that recomposing will move the plane of focus off your subject, but only at the close distances I am talking about. i.e. sitting next to your child at the table or macro work.
The example from your manual is so far away it would not be affected by recomposing.

Ah... ok, thanks

That's it David.
But equally problematic, I suspect that wide open, select focus asks the lens to achieve focus using areas of the lens away from the centre that are soft, so the subject of the image will always be soft, and the best part of the lens has been squandered in an out-of-focus area ??

I sometimes find myself disappointed with the sharpness of my fast lenses, which is presumably down to technique.
I've had a think about it and I suspect that the only way to get the focal point sharp is to use centre focusing on the eye or whatever, and shoot right away without recomposing in-camera.
To get the composition back, the image must be cropped in post, thus moving the sharp bit (from the centre of the lens) to where you want it in the frame. Time for a K3
Normally I frame up in camera using select focus and don't crop (I have never used centre focus and recompose, that's clearly wrong).
Am I on the right lines?
I should point out that this isn't a problem for commercial shots, as I would take several shots and I'm rarely wide open, or that close. It just messes with artistic shots, or shots of the children etc.

I'm looking for that perfect two-body setup for weddings.
Anyone have any experience of this lens?
I had the Sigma 85 1.4, which was capable of stunning results, but seemed to have inconsistent focusing wide open. I decided this was me and I didn't need this length any more, so I sold it.
But now I am looking at the 18-35 and thinking it would compliment my 50-135 perfectly, but I'm worried that dpreview have flagged up inconsistent focusing, so maybe this is a Sigma thing?

These are all well-seen and beautiful. The last one's sky looks a bit of an odd blue, is it just me?
Must go back there...

Lovely!
1 is very serene and beautiful - commercial.
I like the graphic quality of number 2. The last one is a fine shot, but in comparison to 2 I find it a little messy and my eye wanders about aimlessly

Ha, if he had stopped momentarily to look right at me with my K5, I'd have been about 3 seconds too late focusing

These are exceptional Gary; amazingly clear and sharp.
What gear did you use? I'm assuming it was quite dark, or was it fairly well lit on the front?

This is an amazing piece of glass for 20 quid. Everyone should have one of these gems (and some extension tubes to turn it into a serious macro).
Perfect for portraits and great with focus peaking or video, where the smooth manual focus and shallow dof is perfect