To Guillaume- many thanks for your *location*.
It looks that this glass is produced no more, stopped before years. Never mind, but is there a possibility to buy it somewhere? Don't think much.
It's gonna be harder...The most important is optical output, more important than weight. Some tests one probably cannot wait in that times of this lens-production, can he..?
Anyway, it does not look so horrible as someone wrote... It is quite lovely! You should see my 500/5,6...
3kg of weight and 37 filter...(my 300 has 2,2 kg and 43mm). Such a mite...
I am sending many greetings to Lynn from my transport-van!

If you can seriously to do photos of birds (esp.singing) you cannot be *shorter* than 500 (at least!)-or do NOT live in Europe!!!.(my experiences)
600 is nice but nothing special. Good luck with *hunting* them, creeping behind them, staying put for hours etc. If you want to *exchange* some infos about shooting them, here I am:
ante_portas@hotmail.com I am *trying* it for a some time, so *a little experienced*...??
Good advice for the beginning: try to find something more quietness...what about table top first..??? ;-)
With best regards, Pavel