JakTrax wrote:On a full-frame body the 100-400 might be insufficient for airshow photography, however one solution would perhaps be to buy a relatively cheap APS-C camera to give you more reach. This will effectively give you the 600mm of the Sigmas without compromising image quality, and you'll have the flexibility of both FF and APS-C.
The Sigmas are very good but the EF 100-400L wins every time, and I'd always go with any solution that would allow me to get the best quality images.
JakTrax wrote:It really depends on what you mean by 'best'. The lens that offers the best image quality is the Canon 100-400L, and for regular airport photography I'd say it's the best all-rounder. It's also a good airshow lens but perhaps better when used on a body such as the 7D or 90D due to the extra reach.
The 1.4x extender idea above is worth of consideration but is pushing the cost up. Perhaps better to get the lens first and then the extender if you find yourself a bit short of reach. I'd imagine the 100-400L + extender will give similar quality to the Sigma/Tamron 600mm ultra-zooms.
It really does depend on your expectations re image quality. If you want the very best the 100-400L is the lens to get. But it's a lot more expensive than the Sigma ultra-zoom and doesn't go as far. Perhaps you'd be more than satisfied with the image quality from the Sigmas? After all, if you opt not to get the 100-400L you won't miss what you've never had!
JakTrax wrote:If image quality is your primary concern and you want to settle for nothing less than the best, the Canon EF 100-400L II is the lens to buy. If in time you need more reach you can purchase either a crop body (such as a used 7D or 70D) or a 1.4x extender (don't bother with the 2x extender as the loss in image quality is far more significant than with the1.4x). The Sigmas aren't 'sh*t', they're just not in the same league as the Canon.
It's a shame the EF system will never see its equivalent of the coveted RF 100-500L.
In answer to your final question, 100-400mm will be absolutely fine for most spots at most airports.
Military Aircraft Every type from fighters to helicopters from air forces around the globe
Classic Airliners Props and jets from the good old days
Flight Decks Views from inside the cockpit
Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior
Cargo Aircraft Pictures of great freighter aircraft
Government Aircraft Aircraft flying government officials
Helicopters Our large helicopter section. Both military and civil versions
Blimps / Airships Everything from the Goodyear blimp to the Zeppelin
Night Photos Beautiful shots taken while the sun is below the horizon
Accidents Accident, incident and crash related photos
Air to Air Photos taken by airborne photographers of airborne aircraft
Special Paint Schemes Aircraft painted in beautiful and original liveries
Airport Overviews Airport overviews from the air or ground
Tails and Winglets Tail and Winglet closeups with beautiful airline logos