What do you think of these telephoto lenses

[longroad]

Most of my photography work now takes me out into the wilderness where wildlife and birds are my most common subjects, particularly birds at a far off distance. As such I need something that not only extends past my current 300mm but something that won't give me blurred photos every shot.. as yet I havent really taken a bird shot at 300mm that was sharp at 100% crop.
I know getting anything better than f4 means big $$ and Im looking at under $2000.. so what do you think of the following lenses (prices can be seen at the supplied URLs):

Sigma Lens 50-500mm f/4-6.3 APO EX DG HSM
http://www.digitalcamerawarehouse.com.au/prod4085.htm

Sigma Lens 120-400mm f/4.5-5.6 APO DG OS HSM
http://www.digitalcamerawarehouse.com.au/prod3865.htm

Sigma Lens 135-400mm f/4.5-5.6 APO DG
http://www.digitalcamerawarehouse.com.au/prod4448.htm

Sigma Lens 150-500mm f/5-6.3 DG OS HSM
http://www.digitalcamerawarehouse.com.au/prod3027.htm

Sigma Lens 170-500mm f/5-6.3 APO DG
http://www.digitalcamerawarehouse.com.au/prod4452.htm

Tamron SP AF 200-500mm F/5-6.3 Di Lens
http://www.digitalcamerawarehouse.com.au/prod4172.htm

[K1W1]

I hope that you have budgeted for a tripod. There is some serious weight in those lenses.
I suggest that you look at the Sigma sections on some of the popular photo hosting sites (Smugmug, Flickr, etc) and also in Flickr at least any groups dedicated to wildlife photography. You will quickly see what are the popular lens choices.

[Rooz]

not really that familiar with them except the bigma which is pretty highly regarded as a budget tele.

[longroad]

Yes I'll be getting a tripod too... where is the Sigma section on Flickr? I cant find their forums.

[Rooz]

http://www.flickr.com/search/groups/?q=sigma%2050-500mm

type in the lens, (ie: sigma 50-500mm), into the seach bar and look for a group with jut that lens.

[longroad]

The 50-500mm seems to be getting a good wrap from customers, I have a lot more research to do though.

[Telecorder]

http://www.dslrgeeks.com/forum/showthread.php?p=2726#post2726

FWIW, the 170-500 could be considered to be on the low end with the Bigma; Tamron 200-500 & 300 f/4 + TC being on the upper end.

The new 150-500 is showing some promise to be near the Bigma's IQ

[britkev]

Don't take this the wrong way, but before you throw money at the problem I'd suggest you need to try to figure out why you are getting blurry shots at 300mm - if it's camera shake a longer lens is not going to help, and will probably make things even worse, especially the non-VR/OS lenses. The 70-300 VR is pretty sharp in its class, and I'm not sure any of the lenses you list represent a major leap up in image quality.

[Visual Reality]

I agree...the 70-300 VR is probably one of the, if not the sharpest of the lenses you listed here and should not produce blurry pictures. Either you need a faster shutter speed or you need a tripod.

With that said though, usually focal lengths longer than 300mm are needed for this type of thing so I'd go with something closer to the 500mm range.

[faisal]

I've used the Sigma Lens 170-500mm f/5-6.3 APO DG (canon mount) and it's pretty good for its price. I think its downside is lack of OS(which makes hand held almost impossible) and that terrible zoom creep!!!!