EF 100-400mm f/4.5-5.6L IS II vs EF 300mm f/4L IS + Ext. 1.4x III

I won't say it's rare. U are comparing decade old 300 f4 with newest and better made 100-400 II, the latter is as good as my 500mm f4 IS! It's so sharp i have to get one despite not using that much that due to one stop disadvantage as oppose to my 500mm. Most of my shooting is low light.

Recent made high end zoom such as 200-400, 24-70 II and 16-35 IS are so good that unless you need extra stops, there's no point to get the primes. The 100-400 falls in that category. I can't say about other zooms.

Sharpness and overall optics performance is one thing, don't forget that the new 100-400 II also packs better IS that's day and night compare to the ancient origin IS from 300mm.

SnappyChappie wrote:

Daniel L wrote:

Nicer image? Hmmm. Well, i don't have answer that but in term of technicality - Color, contrast, sharpness, focus speed and image stabilizer....etc The new 100-400 II put a whooping on a bare 300 F4 IS. Forget the 1.4x II, there's no comparison.

SnappyChappie wrote:

A year or so ago i wanted a telephoto lens for my EOS 650D, i looked at a number of lens [virtually] around the 300 to 400mm focal length range. I was very interested in the old EF 100-400 f/4.5-5.6L IS (mk1) lens but i didn't like the push-pull zoom function, the EF 400mm f/5.6L USM was a good length - but no IS which i thought was essential for hand-held tele shoots! Thus i disregarded that lens.

So I settled on the EF300mm f/4L IS USM and a 1.4x III extender to increase the FL to 420mm at f/5.6, so a bit longer than the EF400mm at the same aperture but if i don't need that much tele i can just keep it at 300mil @ f/4. I must say I really like the images from the ol' clunky EF 300mm f/4L Expensive though (as they all are!)...

Now, recently, Canon released a new 100-400 lens, the EF 100-400 f/4.5-5.6L IS II USM which looks really good - to have the option to zoom out to 100mil would be useful for sure. So although i'm not in the market for a new tele lens right now i'm still curious as to which lens in your opinions' gives nicer images at their longest length - the EF100-400L II zoom @ 400mm f/5.6 or the EF 300mm IS L with 1.4 extender, so 420mm @ f/5.6? This is a subjective question of course.

So is this one of those rare cases when a zoom lens has better IQ than a Prime? I must say i am quite interested in this lens even more now...