Quote: Dally "On a different note, I am wondering whether a Sigma 150-500mm lens (c. £600) would be worth it? I know their top of the range version (more expensive) can produce petty impressive results, but I am not sure about spending £600 on something which may not be top notch. Do you have any experience of this particular lens?'"
I've never used it. But I would have no concerns about doing so. Of course I always advise people to buy the best glass they can afford. But unless image sharpness and lens distortion are absolutely critical issues I wouldn't waste the money. Professional level lenses are meant for professionals. I'm not saying amateurs should steer clear but you really need to know a good deal about photography before you'll be able to get the best out of a professional lens.
I've seen people throw two grand at a professional 18-55mm or a 22mm-80mm workhorse lens and a 70/200mm intermediate zoom and yet they scarcely know how to operate their own camera. I haven't the heart to tell them they've wasted their money.
I'd definitely be wary of spending big on a 500mm lens. Unless you are a dedicated wildlife photographer shooting at least once per week you're really not going to get a lot of work out of it. My 70-200mm cost me a grand and yet I doubt I shoot more than 5% of my photographs with it. If you are going to invest big money pile it into an everyday use zoom. At least then you are getting value for money.
Quote: Dally "Sadly, Pentax lenses are expensive - c. £1,000 for a 300mm f4 prime lens. Maybe I should have transferred over to Canon / Nikon when I got my last camera! But the Pentax K3 came out better in reviews than the equivalent Canon / Nikon cameras and is a great top end consumer level camera.'"
I began with Canon - simply because it was a big name and the entry level bodies were affordable. I briefly moved over to the Sony Alpha system but even though I really rated the Alpha bodies the choice of lenses was very limited.
I have some very real criticisms of Canon (and Nikon) especially in relation to pricing. But you can't knock Canon's catalog of lenses. For instance I don't know any manufacturer who currently offers FOUR separate professional-standard 70-200mm lenses.
So whilst other manufacturers are undoubtedly forging ahead of Canon and Nikon in terms of camera bodies - all of them are way behind on glass. And as any photographer will tell you - glass is the most important factor when buying into any camera system. Good glass lasts you a lifetime whereas camera bodies are often outdated within 18 months.