theres a lot bunch thread in forum tell about the difference between sigma and tamron.
i just try to make little bit conclusion , because i think, i will get one of them too..
sigma : heavier (bout 60 gr) but smaller .
it has SDM motor and focusing faster in Body that support HSM (K100Ds above)
but it has middle Image quality in long throw zoom ( 150-200)
Tamron : lighter then sigma but bigger body size.
doesn't have SDM motors so the Autofocus speed is little bit slow then sigma ( logic isnt ?? )
Tamron has great Image quality in longzoom (150-200)
which is match for me , because i plan to combine with 1,5 X converter so i can get 300/f4 in long throw zoom .
remind me that DA 300/f4 is still unreachable for me...
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this is my opinion so hopefully you can make a better decision ..so did i :| :| :|
if i miss something or someone have a better opinion ..please correct my answer... im looking forward for another perception
thanks