Apparently, they do do the 500mm f4.5 in Pentax mount, but you have to either hunt it down or order it specially. If you look at the Sigma USA site it does mention it for the Pentax mount and I've seen sites on the web where the photographer is using a Pentax mount one. Deep pockets required.

I recently got a Sigma 400mm AF too. I find it light and very usable. The AF makes a racket, but is quick and locks quickly too. I've had a lot of PF within mine (I'm doing a lot of shots over water at the moment), but stopping down a little and adding a UV Haze filter seems to have helped.

Oh, Clarkly, I don't want to part with it I've also seen a few up on Ebay recently.

The OS version isn't available in Pentax mount. There are 3 variants of the lens, and the only one in Pentax is non-OS (Sigma's name for Optical Stabilisation in the lens).

Looks like good value so long as you actually do not need to pay import duties. Be careful to calculate the cost with the delivery charge.

I love this lens, I've found it to be sharp and consistent throughout its zoom range, though do stop it down to f8 to keep it sharp at the long end.

Xnview does work with DNG files, but I found it to be excruciatingly slow with the big files.

I tried CaptureOne LE and IIRC, it doesn't work with Adobe DNG properly, which is what the GX10 uses.

The two main features I found missing were:

1. Cropping and saving to a specific pixel size

2. No Undo/Redo or action history

I've used the following with my GX10 for processing RAW DNG files:

Bibble - great, but it's missing some features that I use
Adobe PE5 - cheap enough, but again missing features that I use for PP

I've ended up doing RAW conversion to TIFF using PE5 and then I PP in Corel PSP from the TIFF.

You might want to check Bibble as it provides plugins for PS.

Others on the forum like SilkyPix but I didn't get along with it.

Be careful to consider shipping and duties that need to be paid when purchasing abroad. After you add together the lens, postage import duty and VAT, that comes to around £130 for the lens from that seller.

In the UK, a quick look shows that CameraKing (I use them a lot) have them in stock for £165:
http://www.cameraking.co.uk/ViewProdDetails.asp?prod_code=PON05F000129

It fits fine without the TC.

I wasn't expecting to get anything out of my very old Sigma 600mm f/8 mirror lens with a 1.5x TC on it, but it's a fun lens to use and I was surprised with a few of the shots that they actually came off moderately OK:



GX10, 900mm (with TC), F8, 1/640s, ISO 400
.
On a tripod, manual focus, manual metering, image cropped and PP (the lapwing was ~60m away)



GX10, 900mm (with TC), F8, 1/400s, ISO 400

On a tripod, manual focus, manual metering, image cropped and PP (the cormorants were ~100m away)