Used Sigma 400mm 5.6 AF (+ TC 1.4X) VS Tamron 150-600mm .. IQ and Weight ?
I don't want to write too much, but basically, I think getting a 400mm prime could be much lighter + better image quality solution. It's probably pretty close to being comparable to Canon's 400mm 5.6. Both the "Tony Northrup" https://www.youtube.com/watch?v=1fmMG5jgDwk&list=PLwIVS3_dKVpsjSZrQ7H-Nw8GQ7ZuDYyaD tamron review , and http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=278&Camera=453&Sample=0&FLI=1&API=1&LensComp=929&CameraComp=453&SampleComp=0&FLIComp=5&APIComp=0 test indicate, that atleast in canon's case, it seems to be sharper than Tamron. (Canon could also be used with TC 2x to 800mm, and it would still give better results than any Nikon 300mm or 80-400mm TC-ing ... basically @ 800 it's slightly softer than Tamron @ 600)
The idea of Sigma was reinforced when I found that a person has tested the said lens with D800 http://www.csse.monash.edu.au/~carlo/Sigma-AF-400mm-f5.6-APO-A.html . I found these pretty impressive image quality wise. It seems good with the TC 1.4 , so it probably has similiar performance as canon? Maybe go 800mm too?
Prime would weight 800grams less than the tamron, would imo be much easier to handle. It's the fact that canon weights less and also happens to be sharper that this Sigma could be good potential. Does anyone have experience of this sigma, maybe compared it to the tammy?
It's a good lens- it and the 300 F4 APO Macro are both very sharp. It was manufactured in two versions HSM and non HSM AF. If you prefer a zoom the latest Sigma 50-500 OS is sharp throughout the range. None of the 3 can be used with a Nikon TC without alteration to my knowledge as there's a tab on the Nikon that has to be ground off before the Sigmas will mount. The Sigma TC's are a little soft for my taste and AF becomes slow and jittery so I don't use them. I'm currently shooting 800e with a Sigma 500 4.5 prime which is the best of the bunch IMO but hard to find used. I haven't used any of the Tamron lenses.
One drawback of the 400 is it's quite light weight so it needs a beanbag or tripod in lower light.
Hope this helps.