Long end - which one whould you choose ?

I have a K10D with kit lens + 55-300mm zoom. Am looking to buy longer zoom for wildlife/safari in 2009.Have seen Sigma 50-500mm and 150-500mm and would like to know which one is best between 300-500mm. The 150-500 is approx £120 cheaper ,but is it as good as ,or better than 50-500 ?
Help please,

The 150-500 has HSM, but it is unbelievably also heavier and longer than the Bigma, presumably because of the HSM.
If you look at the MTF charts on the Sigma site you can compare the two lenses.
I doubt that anyone has both.

If you are wanting one for safari my choice would be the Bigma, to give you at the wider end, without the need to change lenses. It can be very dusty on safari, and not a good idea to be changing lenses all the time, so unless you are taking two bodies that is something to consider. As are any potential weight restrictions if you are using small planes to get around.

I have the Bigma - the 50-500 and am very happy with it. I got it after going to Tanzania with my Tamrom 28-300, which was just not quite long enough, though I used the wide end a lot as well.

I have a Sigma APO EX 70-200mm f2.8 and have just ordered a Sigma 2X EX teleconverter off Chris at SRS.
If thats any good I will be selling my Sigma 135-400mm if thats of any interest to you.

Not quite 500mm but it will be a lot cheaper.

The dust and weight are both relevant points to consider . Max luggage on small aircraft is 15kg including,I think, hand luggage! Thanks for comments.
Mike

Mike - another thing to bear in mind is the country you are visiting and the season. Kenya/Tanzania allow safari vehicles to roam at will (poss dust issue) whereas Zimbabwe (when it was open), Botswana (I think) and South Africa (definately) confine all vehilces to metalled tracks (no dust). Not sure about Numibia - suggest as SA

If its the rainy season (Kruger in Jan/Feb), then the undergrowth will be such that your 55-300 or an FA 80-320 will cover most circumstances. If it's the dry season, the veiwing range will be greater and a longer lens will be potentially better (though the guides will take you to the areas around the water holes where the game will gather).

I've got a Sigma 135-400 and have my sights on a 150-500. Both are quite heavy and may not be very user friendly in a safari vehicle, more so as the day wears on as using a monopod's not easy in a relatively confined space.

Oh and take 2 bodies if you can (1 with wide to medium zoom, other with medium to long zoom) as sometimes the game gets very close


Steve