asked about sigma 120/300,just seen a 300 f4 L at a good price.any thoughts on quality between both .many thanks in advance.haddock.
I have had both the Sigma 120-300mm F2.8 and the Canon 300mm F4.
I found sharpness of the sigma at F2.8 was OK, but not stellar. The AF was excellent for larger targets but not quite accurate enough for the small birds I was spending a lot of time shooting.
I kept the 300mm F4 IS because it was sharper at F4, lighter, closer minimum focus distance with added bonus of IS.