DA*200 and 2x converters

[pentaxkat]

Out of curiosity has anyone tried the DA200mm with a high quality (7 element) teleconverter e.g. Sigma EX or the more expensive Kenko ones? Whats the quality like say in comparison with a 300mm and 1.4x or a 400mm f5.6 or a zoom like the Bigma?

Obviously if you want reach the 300mm plus 1.4x is probably a better bet (although my M* 300mm is prone to fringing wide open, so I wouldn't want to stick a teleconverter on it, plus I don't think it would handle so well with a converter).

However, I was talking with a friend (who has Canon) and he loves his 200mm f2.8, even for wildlife and it did get me thinking the advantage of a 200mm lens, is you can have f2.8 if you need it, which could make it more versatile if quality with teleconverters wasn't too bad. You could use it at 200mm for general travel or larger animals/animal in environment portraits and use a 2x for more reach.

I'm not able to afford the DA*200 or anything but I always like to find out about Pentax lenses and kit trade-offs. At the moment I need to improve my technique with my 300mm (which is a lovely little lens; I'll stick some photos up with it at some point when I've sorted through a load). I like having a really portable tele and stalking birds up close handheld with some fill flash. The DA*300 looks rather big for Pentax (but still very nice!).

[Lowell Goudge]

I have a sigma APO 70-200 F2.8 EX and use it with both the 1.4X and 2X sigma TCs.

I have this for the exact reasons you state. when I only want 200mm Maximum, indoor sports, biugger wild life etc. I take off the TCs and have a very fast lens.

I find for longer situations (birding especially) the TCs don't really cost me anything in IQ that I can see.

The only issue is that at present, pentax does not recognize the USE of TCs and the focal length and apature data fed to the camera is that of the main lens. The impacts are as follows:
- your focal length will be incorrect for shake reduction
- the metering may (dependant on camera model) be off by as much as 1 1/2 stops. At least it is on the K10D.

The latter is due to the behavior of the K10D focusing screen, which has a non linear behavior with metering as a function of actual F stop. This seems to be compensated for within the camera with A series and later lenses, BUT without having the correct F Stop for the lens plus TC gets the compensation a little off. I have posted regarding this issue previously

The real issue you need to watch is that Sigma TCs are unique in design, with a very prominant (it sticks out) front element arrangement that cannot be used with many other lenses.