I am hoping to get some feedback on a possible switch I've been contemplating.
I currently have a Canon 300mm L f4 IS prime lens (2007 date code). I also have a Canon 1.4x extender that I often use with it for "birding". The lens is very sharp, in absolutely perfect condition, original box, soft case..etc...So I'd assume I could sell it easily.
For about what I think I can sell the lens for....maybe even for a little less, I can buy a new Sigma 150-500...that lens would obviously be more versatile as far as focal length, and also fill in the 200-300 mm "gap" (not including use of the extender) I have between my current 300mm prime and my 70-200 f2.8 IS.
I realize that the Canon 300 is a faster lens by about a half stop at 150mm on the Sigma, and the Sigma is not a constant aperture lens (I think it's f5-f8 or so). But it also has a good deal more focal length... using the extender the 300 gives me an equivalent of 420mm and with a crop sensor about 680..the Sigma would give me an 800mm equivalent just with the crop sensor, and if the extender would work, it would put it at about 1100 mm.
I don't know if I can use the extender with the Sigma, or if I can if I'll lose auto-focus?
I'm not sure what it would be like to hand hold the lens....the 300mm prime is pretty light, and focuses quite quickly and is lighter than my 70-200 (although not by enough to make me aware of the difference when using either).
The Sigma does have their version of USM and IS..so it seems to be a lot of lens - other than the slower and non constant aperture. But I use a long lens like that almost exclusively in bright daylight..in fact I rarely take my polarizing filter off the 300...so that brings the f4 down by maybe a full stop..give or take.
The Sigma does seem to get good reviews and buying a new one, if I get a bad copy, I can always exchange it. Or get a refund if I just don't like it (it would be hard to find anther 300 Canon in the shape mine is in, but I guess with a bit of patience I could eventually find one.
I've never seen or held the Sigma in my hands, and don't know of anywhere in reasonable driving range to check it out. I assume the build quality is good..don't know how it would compare to the Canon (which isn't one of the best built "L" lenses, (not weather sealed), but is still build like a tank and has the built in lens shade which is great (but useless with the polarizing filter).