Talking to the converted

I was lucky enough to pick up a Sigma 70-200 2.8 EX APO from a forum member here and need some advice.
I have picked up on a few threads re sigma converters and have a few questions.
Is there a noticeable difference between the 1.4 and2X converter?
As the converters are "DG", will they actually improve results for this non DG lens?
Using a K5, will AF be maintained and focus as quickly?
Is there any reason apart from size to keep my Ashai Pentax 2.5? If I keep it, can it be used with good results on the converters?

The lens arrived today, and was only able to stick it out the window for a few quick shots, so the squirrel had to have it!...would a monopod improve on these? [heavily cropped]



[IMG]http://img.photobucket.com/albums/v425/inamini/IMGP6846.jpg[/IMG]





[IMG]http://img.photobucket.com/albums/v425/inamini/IMGP6851.jpg[/IMG]

Thanks folks.
Nigel

I have the same lens plus 1.4x and 2x DG converters

Yes, with the 1.4x you get very little quality loss .. the 2x is really only for emergencies.

No

Yes, AF is maintained with both lenses .. speed is ok with the 1.4x but not so hot with the 2x

One thing I will say is that mine needed a bit of AF adjustment to get it spot on.

Great lens though ....



Paraglider at Barton Cliffs by Mike.Pursey, on Flickr



Motocross Crop by Mike.Pursey, on Flickr



Squirrel by Mike.Pursey, on Flickr

Hi Mike, thank you for the rapid and full reply. You have a good eye, and those are great captures. Are they all hand held?
Nigel

Yes all are handheld, personally I never bother with the monopod although I suppose I should really.

To prove how good the lens is with the 1.4x converter look at the first shot .. see the bird on the ledge to the right?



Bournemouth College Clock Tower by Mike.Pursey, on Flickr

Now take a look at the 100% crop .. again handheld.
Remember, these were done on a K10D .. imagine them now on the K-5.



100% Crop Peregrine Falcon by Mike.Pursey, on Flickr

Spot on! I will have to check the accuracy of the AF and then try and source a 1.4X.
Many thanks Mike
Nigel