You have to stop it down using the stop down lever (around the shutter release) or the green button.

This means manual exposure only and stop down operation.

It does work, and it is a cracking lens. Using it at f1.7 all the time would be very limiting though.

I wonder why this particular issue is so rare?

Sorry Dan, I've just checked and I have the same issue missing as you do. That's a weird coincidence.

A lenses will actually work perfectly well in all exposure modes.

All the best, Gordon, have a great Christmas!

Very much over-sharpened and I have the feeling that the underlying image is not ultra-sharp to begin with.

Also, I agree it's a bit tight in the frame.

Is this the new 10-1000mm f1.4 zoom?

Good to hear a positive experience, thanks for sharing it.

When you have some images, why not post a few for us to have a look at?

These figures for the 12-24mm will amaze you. They are taken from the recent AP test on the pentax and Schneider lenses. The values are, unsurprisingly, the same for both.

At 7.5m distortion is -0.6% (12mm) -0.2% (18mm) + or - 0.05% (24mm)
At 25m -0.46% -0.15% 0.15%
at Infinity -0.31% -0.1% No value

These are remarkable results and a superb bonus to such a useful ultra-wide lens.

If anyone wants to check a lens for distortion, then you need a nice square-on flat subject so you can see the effect on straight lines near the edge of the frame.

A wall or building could serve, but a closer subject is useful to see how distance affects things.

If you have a critical use in mind, then something at the same distance as you would normally be working is appropriate.

A flat document will show diistortion up very quickly. General shots disguise the distortion very effectively, so are not the best way to evaluate it.

Hope that helps!