i would describe the sigma apo version as excellent.. the cheaper variants are nearly as good.. mine is very usable (focuses well) and sharp even wide open at 300mm..
none of the current 70 to 300mms are bad even the cheapest tamron version which is still sharp wide open but might have a few more fringes..
not much choice thow unless u want to spend vast fortunes for faster glass..
there might be bad copies about thow i dont know..
trog
ps.. i have sample pics from the sigma apo and the cheaper tamron.. also from the tamron 18 x 200.. sigma 28 to 300 and a few other super zooms like the tokina 35 to 300.. and my panasonic fz20 bless it.. he he
Last edited by trog100; 12-29-2006 at 08:04 AM.