safari lens

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been looking for a telephoto lens to take to kenya with me next year, have got a budget of around £600, he lens will be paired with my d90.
couple lenses ive been looking at are
* sigma 120-400
*sigma 70-200 2.8 + 2xconverter

are these lenses ideal? or is there anything else i should consider within my price range?

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also with the 70-200 and x2 converter, i know i will lose two stops, but will i lose auto focus?

[phototuition]

120-400 Os is, I hear an awsome lens and much favoured by birders. Is there a 70-200 os? 70-200 will be at a constant f5.6 and autofocus should work ok. 70-220 more useful once back home but only if OS of course. 120-400 more a dedicated wildlife lens.

70-200 2.8 will be ok on crop sensor for larger and closer beasts and you'll benefit from the f2.8 as long as it's OS. Converter might compromise quality which is crucial on safari due to early and late in the day shooting and low contrast due to animals blending into surroundings.

Might be worth asking Andy Rowse if he still does warehouse express.

No personal exp of any of the optics but one of my trainees loved the 120-400 for birds.

[fox in the box]

Smalls,

I picked up the Sigma 120-400 yesterday from Jacobs digital after months of indecision. This is also for use on a safari and now I have it I can't wait to go!!

Personally I'd go for the 120-400 over the 70-200 + converter. I haven't seen any images taken with the latter but on some lenses the converters do compromise images quality somewhat.

[Jack Flash]

A mate of mine bought the Sigma 120-400 last week for his D90.The pictures he showed me on Sunday were very good and sharp at 400mm.
I will certainly be buying one for my D300 in the near future.
He paid £629,but they can be bought for £599.

[x777]

Just keep the Sigma at f8 or higher and it'll give you good results. At least it's (usually) sunny on safari!

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cheers for the replies guys, looks like its guna be the 120-400