Advice needed, Need a new telelens for my Canon 7D

Started Feb 3, 2013 | Discussions thread
rextal Junior Member • Posts: 39
Re: Advice needed, Need a new telelens for my Canon 7D

My vote is for the Canon 400mm F5.6 L.  I switched from the Sigma AF 120-400mm f/4.5-5.6 DG HSM OS to the Canon 400L f5.6 and have never regretted it.

My initial experience aside (returned 2 Sigma lenses due to faulty OS and faulty focus motor) the third and I guess indicative to this lens had to be stopped down to f8 at 400mm to get decent quality images.  Beyond about 350mm the image started to suffer, which is not abnormal with cheaper zooms.  On the other hand the Canon is sharp at wide open f5.6, I kid you not.  It does lack IS but go to ISO 400, a pinch with your 7D and it will repeatedly produce excellent pictures.  It is also a better image quality than the Canon 100-400L and focuses faster than both the Sigma and Canon 100-400L.

I'd wager it'd still be sharper than both those lenses with a 2X teleconverter.  

However it is a prime so no zoom, which may not suit air shows where you get to walk around the aircraft.  Though for that 70 or 120mm is still too long and you'd probably want something like a 24-105 or such.

And speaking of what may not suit airshows, I thought f2.8 would be too shallow.  Planes are big objects and a formation of small planes requires a decent depth of field.  I'd guess you'd want a bare minimum of f4.  I have enough trouble with a bird at f5.6.  All lenses set to a given aperture should theoretically let the same amount of light in and require the same shutter speed so using your f2.8 at f4 or f5.6 is no different from having an f4 lens at f4 or an f5.6 lens at f5.6.

So from that point of view image quality or reach is perhaps the deciding factor.  I'd only go an f2.8 if you thought you'd use that lens in low light or deliberatelly wanted to isolate the background, which I like for birds.  Not sure you'd have too many issues of backgrounds interfering at airshows.  Even trees at take off are usually sufficiently far enough back to be blurred at f8.  And don't forget to factor in the extra weight of f2.8 lenses (generalisation but usually true as they have bigger glass).

P.S. As many lenses require stopping down to get the best result, there is some merit in getting an f2.8 lens as by the time you get to f4 you may be at the sweet spot.

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