Airshow lens choice

Lancer3397 · 2013-07-29T00:17:14+0100

I'm a 3 year pentax user and have progressed from a K-X to a K30 in that time. I have the kit 18-55 WR and the 55-300 lens and am now looking to expand my lens collection with a focus towards long lenses for airshows. I find the 300 okay but would like longer reach and seem to have settled on Sigma as the lens manufacturer of choice. Sigma 120-400 Sigma 50-500 Sigma 150-500 I have read that the Tokina 80-400 is pretty good but that's quite an old lens now and also like hens teeth in trying to find a good example. And when it does appear it's a big price. My thinking is if I'm going to pay big money, then I may as well pay big money and get a new lens with warranty etc. I like the idea of the 50-500 as this gives me good reach but also allows me to shoot reasonably close subjects on the flight line if I need to without having to faff and swap lenses. at Duxford Flying Legends two weeks ago I bumped into two other pentax users. one had the 150-500 and the other the 120-400. both agreed the 120-400 had slightly better image stabilisation built into the lens. now obviously the 400 lens is a lot cheaper but I also read on this forum that of the 150-500 and the 50-500 the 150 is a lot sharper. My main requirements are sharpness and reach. I use a hama shoulder mount so I can keep the camera nice and steady. Of the 3, does any edge it over the other? Alternatively, older Sigma 400 primes are available, what's the view on one of these.