Kiwikat wrote in post #14016883I don't know that I would really endorse the 300 f/4 + 1.4x combo. It really hurts the AF performance and increases CA. It is also noticeably less sharp.
If you want 400, get the 400 5.6. Personally I'll be waiting for the 100-400 II or whatever they end up calling it. Not sure if I'll sell my 300mm then or not. It is the PERFECT dragonfly and butterfly lens, especially with an extension tube.
It's not perfect, but it's more verstile than a 400mm alone, and I think superior to the 100-400 at 400mm (but I'm also not a fan of push/pull "one-touch" zooms, just a personal preference). 1969 Ford GT-40 Turn 2, 2009 Rolex Monterey Historic Races, Mazda/Laguna Seca RacewayEF 300mm f4 IS lens with EF 1.4X II teleconverter, effective aperture f5.6 (wide open). EOS 50D camera at ISO 200, 1/1250 shutter speed, handheld or monopod, avail. light.
I can't speak for all the different available teleconverters, but 300/4 with Canon 1.4X Mark II focuses fast enough to keep up with cars going by at 100+ mph...
And - IMO - the combo I use is sharp enough to gather up gobs of fine detail... Young black-tail mule deer buckEF 300mm f4 IS lens with EF 1.4X II teleconverter. EOS 5D Mark II at ISO 1600, 1/400 shutter speed. Handheld or monopod, avail. light.
No lens is perfect and any teleconverter always costs some IQ. I feel that my 300/4 works well with Canon 1.4X II in particular, but it may or may not be as good with other 1.4X TCs... I can't say from personal experience. And I find a couple minor issues with 300/4 alone...
Some key things I see with the 300/4 are...
It's IS is an older & simpler version, probably good for 2-3 stops effectiveness, but it must be turned off manually if the lens is locked down on a tripod (the same is true of the 100-400).
Also, the 300/4's background bokeh can be a bit harsh. Particularly with busier backgrounds where you don't have a whole lot of separation and when not using the lens wide open. The below image needed some work on the background in post-production... DeterminationEF 300mm f4 IS lens at f5.6. EOS 7D camera at ISO 400, 1/2500 shutter speed. Handheld, avail. light.
I'm hoping that when Canon revises the 300/4 some day they'll use more and/or curved aperture blades to enhance the bokeh a bit. As with most any lens, wide open the 300mm has a perfectly round aperture and will render really nice background blur. It's when you stop down that the background blur isn't as nice.... but it depends upon the background, and upon how much distance there is between photographer and subject and between subject and background... and it can be dealt with to some degree in post-production.
I also use the 300/2.8 IS when I can and it's sharper, its backgrounds certainly are lovelier, and it's AF is nearly instantaneous. But when I have to trek any distance, a tripod isn't an option, and/or I have to handhold all day long.... I'm far more likely to use the 300/4!
I haven't seen significant chromatic aberration with my lens, with or without teleconverter. However there is an odd purple or magenta fringing effect in highlights that's somewhat of a hallmark of the 300/4 IS... It's easily fixed in post production... Here's an example that I left uncorrected (because I didn't feel it detracted from the image)...
Note the two catchlights in the bird's eye... Redtail hawk flybyEF 300/4 IS lens at f5.6. EOS 5D Mark II camera at ISO 800, 1/8000 shutter speed. Handheld, avail. light. I can tell you that the 300/4 (and 100-400 for that matter) doesn't like filters. I've seen more than a few people surprised how much better their lens performed, once they removed a "protection filter" they had on it! Some filters seem to cost more image quality than a good 1.4X teleconverter will.
But there are many choices. 400/5.6 without a TC will be about the sharpest and best IQ, short of going to a far more expensive super tele....However it lacks IS, so plan accordingly. The Canon 100-400 and three Sigma long zooms are very versatile, no doubt about it... though at the long end they all are a little less sharp/lower contrast & saturation than an equivalent prime or some primes + 1.4X. For me, the 300mm + 1.4X is a good option and works out well (when I don't want to deal with the bulk of the 300/2.8, which works extremely well with 1.4X and pretty darned well with 2X too). I'd like to try the Sigma 120-300 OS and a 1.4X some day, as well. And when I win the lottery, I'm going to get the 200-400/4 Extender (if Canon ever stops talknig about it and actually puts it out on the market)!
The 500/4 IS is a spectacular lens, too! But it is a big, pretty much "tripod-only" and for wildlife and similar subjects a gimbal mount of some sort is pretty much a necessity (I use a Wimberley Sidekick with a Kirk BH-1 ballhead) . Budget $1000-1500 US in addition to the cost of the lens, for a good, solid, tripod setup. The 500mm ("Mark I", the new Mark II is slightly smaller) will fit into a larger backpack, but won't leave much room for other lenses and gear. It's also harder to get and keep on target, with it's relatively narrow angle of view.
The 600mm.... Well I don't use it but considered it at one time, but ruled it and the 400/2.8 out completely just based upon sheer size and weight. Both are bigger and heavier than the 500/4 (or for that matter the 800/5.6). The newer Mark IIs of these lenses are a bit smaller and lighter, but not still not lightweights by any means, still pretty much tripod-only. The Sidekick type of gimbal mount is not recommended with these larger/heavier lenses. Yeah, I know some folks use the Sidekick with them, but a full gimbal head that replaces the standard tripod head and "cradles" the lens mount underneath is recommended instead. That means a tripod that's pretty much dedicated to use with that particular lens (unless you are willing to haul around and swap out a second tripod head, when you want to use it with the rest of your gear).
And, with 500mm or longer you are often shooting through a whole lot more atmosphere than with shortre lenses... so there is some loss of IQ that's no fault of the lens, camera or photographer... Getting closer with a shorter lens is the only solution. I use 500mm a lot less often than 300mm... For me the 500mm is most useful with small subjects... and/or on FF cameras (where it's much like a 300mm on an APS-C cropper)... And I'm more likely to use it when I have an ATV or 4x4 transport, so don't have to hike very far with the lens!
There's no substitute for getting closer to your subjects, when it's safe to do so... That will always assure better results. Practice stalking skills, use hides and attractants, whatever.... I know wildlife and scenic photographer Nial Benvie longest lens owned and used for the first tend years of his career was a Nikkor 300mm + 1.4X, and that was all on film/FF. He managed somehow!