Originally posted by OrenMc Ben I seen your review of the A 400 f/5.6 you have and the price you paid. What would be in your opinion the most one should pay for that lens.
Oren, this question is hard to answer, as the same Pentax lens nowadays may be sold for its weight in gold or can be had cheaply, because the auction went unnoticed... I bought mine from KEH, which has the advantage, that there item condition rating is quite o.k. and they provide great service, if something is not as it should be. That was worth perhaps + 70 USD on an auction price.
The prime question is, what it is worth to you: The image quality is superb, but the handling is slow, especially at short distances (due to the focus rotation angle). It has no AF, so manual focusing comes into the play, too. So, if you are a happy MF user, this doesn't matter too much, otherwise it would be an important factor price-wise. The later FA 400/5.6 is an elusive lens. I have only know it from an old Pentax catalogue and I think, I have seen one recently for sale second-hand in the region of 2500 USD.
In terms of image quality there is no other affordable lens for Pentax, that can be compared to the A. The FA 400/2.8 is another price league, though its IQ is perhaps better. The Tokinas, Vivitars or Sigmas in that range are all not as sharp. So the choice is limited to the A 400 or something like a 300mm lens + tc. One alternative could be zoom lenses, like the Tokina AF ATX-80-400 and the like. I have the Tokina (first generation) and I have never used it for anything just for test shots. If anybody wants it, I sell it. The Penntax blows it away quality -wise.
If you consider that old MF Tokinas, Sigmas etc. regularily go for 200 USD on ebay, the Pentax really is worth 400 USD, provided the lenses and the aperture and the focusing action are all flawless. The problem is, (short conclusion to a long post): there is simply no real alternative. 400mm lenses are today very rare. As far as I know, none is available new for Pentax now (not from Pentax, but even not form Sigma, Tokina etc.), so at the end of the day, if you really want it, you have to pay whetever the seller asks. But my limit for ebay would be 400 USD, KEH or any other reputable dealer a bit higher - just what I paid.
One intersting alternative springs to my mind: the rare Tamron 400/4. It is a very rare lens, but highly praised. And I would have bought it recently, hadn't I not just got the 300/2.8. The 400 Tamron is super-sharp and has, I think IF (inner focusing), which makes it a bit less tedious to use. But it will be a bit more expensive, as you usually would have to buy an Adaptall PKA adapter on top (which costs 80-100 USD). This might be the only lens, that could perhaps rival the Pentax A and is affordable.
Ben