Confused over choice of lenses

[AndrewKulin]

I own a 300 mm f/4.0 L + 1.4 TC-II and these two pieces are mated together. Used on my Canon 40D and excellent image quality. Gives a 300 m x 1.4 x 1.6 = 672 mm FF equivalent on the 40D (and 7D) (and the 1,4 TC add 1 full stop so f4.0 --> f/5.6 (which is the AF limit for Canon non-pro lenses such as the 40D). I cannot say I have noticed an appreciable loss in AF speed with this combo on my 40D.

The 500 mm Sigma (and I doubt it is compatible with the Canon TCs) would give you a 500 mm x 1.6 = 800 mm equivalent. Some extra reach for sure, but note that at 500 mm it is rated f/6.3 which might impact your AF speed, and as someone else noted, they said it gets soft around 500 mm.

Weight is another thing to consider how heavy is this lens compared to a 1.4 + 300?

I also see you are looking to use this at an airshow. Very difficult from my limited experience (at airshows) just getting a fast moving (small) object into your view with such a narrow FOV. Just to make this decision trickier, a least with a zoom you could zoom out to find your jet plane and then zoom in while tracking it.

[cosmicma]

i also have the 300mm prime and 1.4 teleconverter and it's a fantastic combination
i also have the sigma 170 - 500mm which bought a few years ago which is now gathering dust
the sigma is a good budget lens but falls way short of the canon L variety

there's 2 choices if you have the money my first choice would be the 300mm prime and add a 1.4 teleconverter at a later date or the 100 - 400mm L both are very good lenses the 100 - 400mm ads a little more versatility with the sacrifice of a small loss in image quality

another to consider would be the 400mm f5.6 L prime from canon a lot of people swear by that lens

[Markulous]

Another to consider is the Sigma 150-500 OS which I use (and prefer over the Canon 100-400 IS even though I love the pump zoom and build - hate the silly colour) which I tend to take over my Sigma 500 f/4.5 if I'm not after wildlife, specifically. Not used the original Bigma 50-500 nor the OS version but was never interested in a zoom which went down to 50mm - too much compromise (but acknowledge that both lenses can take superb pics!)

But I do love my Canon 300mm f/4 IS and, if situations suit, will use that as that'll beat any of above for sharpness. Iideally, I'd do away with zooms and just use primes - except I love what my Canon 70-200 f/2.8 produces (and need the zoom for the shots I take with it). Also the 500 weighs a fair bit!

Do have a Kenko 1.4x TC and use that on all of above (and have taped contacts to ensure AF works - and works well with my 20D/30D/7D). Dumped the Canon 1.4x TC as I found the quality the same and Canon will only fit Canon L lenses (plus I got the Kenko for a 1/3rd that I sold the Canon!)

[ian clark]

Give "the Boss" the cash and let her choose.
That way any problems you can not be blamed

[Markulous]

Originally Posted by ian clark

Give "the Boss" the cash and let her choose.
That way any problems you can not be blamed

If I did that she'd ask for £10k, choose the Canon EF 500mm f/4.0L IS, pocket the change and then make me carry it for her!