If I had a US$10,000 600/4 I wouldn't be shooting with a 7D

There is the potential, if you use your shutter release button for both focusing and releasing the shutter (it's default postion), for losing focus at the critical moment or failing to lock on because you have the 'do not fire unless in focus" (focus priority) setting enabled (again that's the default).

If you remap your focusing to the AF-S button and leave the firing of the shutter to the shutter release button, plus change the setting to shutter priority instead of focus priority, then the shutter will fire independently of the focusing button (now AF-S) and you will get more shots because the camera is not waiting for focus confirmation - which is sometimes the case that even though for a fraction of a second you had the bird in focus the focus confirmation could ignore this because you lost focus again. This allied to burst mode should give you more keepers.

Neil. Gulls shouldn't be difficult, they are large and relatively slow moving. It's possible there is a problem with your technique or settings. Can you tell us how you hold your camera, whether you use a tripod/monopod and the settings you generally use for bird photography ?
I used the K5 and DA*300 for 2 years (with and without the AFA x1.7) and found it very good on larger birds, it was on smaller birds with frenetic feet, or flushed birds, where it had difficulty. In all cases a degree of anticipation is required though.

Here are some samples all with the K5 + DA*300

Thanks Was. !

There are climbers !?!

I still haven't found them ! Where are they ?

Brilliant pano.

Thanks Giofi. I'm not trying to blow any horn but in this instance at least I thought it was what the OP was looking for, a valid comparison.

Everyone on here knows my opinion of you and your integrity so your views on anything have zero interest to me.

When is the last time you actually posted a shot you've taken on PU BTW ?

Do me a favour, if you see one of posts skip past it and you'll save us both making posts we'll regret.

It is a complicated question and will undoubtedly depend a lot on exactly what is being tracked, how large it is in the frame, which lens and camera combination are being used and, for sudden changes in subject distance, where the focus was in the first instance (e.g. were you shooting at the MFD and then suddenly to a BIF at infinity) and of course the distance from the shooter (smaller object).

Having been paid to shoot a fair few sports events I would have no hesitation whatsoever recommending the K5 for rugby (which I shot),, football, tennis (which I shot), hockey, X games (which I shot), motor racing, moto-cross etc. etc. In my first year I used 2 x K5 with the Sigma 50-150 and DA*300 and they performed very well indeed, the failure to lock focus was relatively far and few between, I'd say a 90%+ success rate.

Last year I also used the Nikon D800, Sigma 500 and Nikon 80-200 in addition to the K5 kit. There is a distinct advantage in AF speed with the Nikon, even when used with the 500 (the 80-200 is lightening fast). I would often be shooting with the 500 and put it down to pick up the 50-150 (which with HSM is a little faster than most Pentax lenses) as the players came close to my pitch-side position and the speed difference is noticeable, but that said the K5 didn't fail me and no make/combination has a 100% success rate.

So yes, the Nikon AF is faster (and their 300 primes, whether f2.8 or the f4, are all very fast focusing lenses) and there are/will be instances where it will get the shot and the K5 would miss, but they are usually specific circumstances and the K5 will get 90% of the shots the D800 would. Of course that 10% is part of the reason I added a Nikon kit - birds are tough when they suddenly take flight from the bushes !

That last paragraph is spot on Chris. Sites such as Lenstip, for example, go as far as to stress that point in their testing.

However that said it is far too simplistic to say that 'contrast' per se is what is required for a lens to demonstrate 3D rendering and there is always debate when this subject arises as to which photographs are 3D and which aren't !

Whilst the opinions on what is required for any lens to produce 3D images is even more diverse. Suffice to say that contrast alone is not the sole requisite, distance from subject to background and from the subject to the lens, angle of light source, sensor size, quality of light, separation of the subject from the environment (often of course easier with wide aperture tele lenses or indeed just a tele lens) and many other factors are often considerations.

It is not a pure science and that is why I said that Zeiss (Contax and ZF/E) lenses demonstrate some superb 3D rendering, the 100/2 I mentioned especially but the 35/2, 35/1.4, 50/2, 50/1.4 and 85/1.4 are superb too as no doubt the new 135/2 is/will be. For indisputable examples please just take a look at the very long Zeiss threads (there are a few) in the Alternative Lenses forum at FM. Those examples showing 3D rendering just jump off the screen.

Excellent ! Great sequence - love the action. Pheasants might be as common as muck to some but personally I don't see them that often and from a photographic standpoint love them, they have gorgeous colours when seen up close.