Hi Jack,
Thank you for all of the useful info, I will get the sigma

hope to be able to get out over the weekend to go and have a look at one.
I was thinking earlier that I might have a go with the macro setting something that I have never tried before, Marks one handed shot of the dragon fly is quite good considering it's a snatched shot, nice colors.
Jack some nice images in your album, I like them. A blowy thing! not very technical Jack.
Take care
John.