Canon 100-400mm vs 300mm F4L+1.4tc

[Brachytron]

I am looking to buy one of the two lenses mentioned in the thread title, mainly for BiF and DiF (that's Dragonflies in Flight!). Does the AF speed reduce significantly on the 300mm with the 1.4tc attached? Can anyone offer images of BiF taken with either of these set-ups. Many thanks..

 

[MatBin]

I have read the TC does degrade the image a tad so for the best IQ you'd probably be better off with the zoom, add the loss of light meaning you'd have to reduce shutter speed or up the Iso and the zoom is looking even more attractive. My 50D is a bit dissapointing above 800 so I'd be looking at getting the best image via the aperture/shutter speed combo rather than upping the Iso.

 

[HoppyUK]

You can compare anything to anything directly on this website. This link should load with the 300 + 1.4 extender vs 100-400 at 400mm, both at f/5.6 http://www.the-digital-picture.com/...meraComp=453&SampleComp=0&FLIComp=7&APIComp=0

If you're unfamiliar with The-Digital-Picture.com, you'll need to spend a couple of minutes reading up a bit to understand what you're looking at. FWIW, in terms of sharpness there doesn't seem to be a huge amount to choose between them in this comparison.

If you want to see how good it can get at 400mm, load up the 400L 2.8 for comparison. It's sharp...