Hi,

I have a Pentax K10D with a Sigma APO 100-300mm F4 EX DG lens and have bolted my new Sigma APO 1.4x DG AF on, and am having trouble with the auto focus.

I've got it set on the "P" setting and AF.S, shake reduction is on.

On the lens I have autofocus set and the ring set to A.

When I hold the shutter button half way down all I get is a whirring sound...

I add the TC to the lens and the put this on the body as you are supposed to, both the TC and the lens are digital ones, not old film ones.

I've checked on the Sigma website that the TC is compatible with the lens.

Any ideas or advice?

Thanks.

Thanx,

George - if I could get closer believe me I would

The vessel is a cruiseferry and the deck is 34 metres above sea level, so you can see my problem!

Guys,

I have a Pentax K10D and need a good lens for taking wildlife pictures.

Mainly they are dolphins - so shots of fast moving animals taken from a moving ship at a distance of 800m to 2km, at sea (so some glare)

I've narrowed it down to either:

- Sigma 150-500mm f/5-6.3 DG HSM

or

- 2nd hand Sigma 100-300mm f/4 EX DG IF HSM APO with Sigma 1.4x EX DG Tele Converter

I'm guessing a good quality CPL filter would be a good idea too.

I've already tried shots with a Tamron 70-300mm F/4-5.6 Di LD Macro but the results arn't great, often grainy or not sharp.

Any recommendations?

Cheers.