All of the advice is excellent and with the possible slight deviation of the 120-400 Sigma very consistent. I have followed exactly the same route as Alan (Blythman)but independently, not realising what he had been doing. It was borne from experience in the field. You can see that development here if you go back in time with my Flickr pics. Currently mostly with the DA*300 but even more recently with the 1.4x converter. So the advice is good, it's just for you to decide the budget!
Dave

https://www.flickr.com/photos/dcweather/

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I would add to that. Frankly my 300mm DA* effectively can't track in continuous mode. Tried all sorts of the available options. Is the lens faulty, the camera faulty (K3) or is in truth just the way it is?

Every time I spend more money I think I'll get some back on the 55-300 as I can cover all those focal lengths. I never do though because it is such a bargain and so versatile. I'm glad I didn't. I took it abroad with me recently, got some great birding shots and remembered what it was like to travel light. Unless I fall on some seriously bad times it will never go!
Dave

I've got both and might soon part with my 150-500 but am dragging my feet. The zoom is the boon! It is very good quality but once you use the DA*300 you want to use it all the time. I have just got the 1.4TC and the IQ and focusing seem as good, possibly even better though I don't see how it can be unless the contacts for focusing are better than on my DA*300.

Seems to work ok
With 100mm macro:-

Well I'm up to see my brother in Durham at the weekend and then off to the Farnes with two chances, Sunday and Monday so fingers crossed. Just hope I can get some shots as good as yours. Will probably take my 300 + the fab new 1.4x converter. Do I need something shorter as well, maybe the 100mm + converter although I will have the 18-250 for any wider shots.
Dave

Me too today. Tried it with my 100mm macro for butterflies and wow! Was I impressed. Focused the same or better and I couldn't see any loss in quality.






Dave

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I would say the glass transmits the light. The better the glass the lower the modification. The film or the sensor produce the image. You can change either the film or the sensor and alter the amount of noise which ultimately affects IQ .

As you can see - I like to keep in trim

5th from the left in the back row - and mine isn't a perm !

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.. and now with some of my likes :-



Dave