johnwhit wrote:
The (now discontinued) Tamron 1.4x TC is pretty good and fetches a good price. The Pz-AF Teleplus (Kenko) 1.5x, 1.7x and 2x 7 element are the best available at present if you want SDM compatibility.

John

rparmar wrote:
I fill the 24mm and 28mm slots with decent Vivitar primes. I don't care that they are manual focus, but I imagine much of the market would. Maybe I should be keeping my eye out for an FA 135/2.8.

Algernon wrote:
I've already stated in another thread that to anyone doing nature photography FF offers no advantage, unless you can get as close as you want too. If you have say a 400mm lens you will need to buy a 600mm lens to get the same shots......... but if your going to buy a 600mm lens you might as well use it on the APS-C and completely fill the smaller frame anyway.

rparmar wrote:
Hi John, this is a good discussion to have. Nice to get your potted history of focal lengths! One day I have to get a "swinging sixties" fisheye. Never wanted one before now, but that phrase has done it!

The lenses I suggested are not necessarily because I would want them (though I might) but because they are gaps in the existing line-up. I try not to be too self-centred on matters like this... just enough to be interesting! To that end, here's a list of the prime focal lengths Pentax makes available:

14mm
15mm
21mm
31mm
35mm
35mm macro
40mm
43mm
50mm
50mm macro
55mm
70mm
77mm
100mm macro
200mm
300mm

Where are the gaps? Taking into account that field of view is not linear with focal length, between 21mm and 31mm and between 100mm and 200mm are ill-served. Plus longer focal lengths than 300mm, though Pentax tried offering one of those and no-one wanted it.

mph555l wrote:
I'd like a DA10 limited, and a DA8 fisheye limited.

(And a lottery win to pay for them..)

Cheers,

/Ian