Pentax 250-600mm f/5.6 ED IF SMC P-FA
(From Pentax lens literature) The unique Pentax SMC P-FA 250-600mm f/5.6 ED IF zoom lens provides a moderately long zoom to extremely long zoom range. It features a fixed aperture setting of f/5.6 throughout the zoom range and uses a 43mm rear filter. An internal focusing system ensures faster and smoother focusing while a high-refraction extra low dispersion (ED) glass element produces high-resolution, high-contrast images with true-to-life color rendition. This lens is great for capturing candid shots from a distance.
Pentax 250-600mm f/5.6 ED IF SMC P-FA User Reviews
10 out of 10 points and recommended by Marc Langille (1 reviews)Optical quality is superb - even wide open; unique FL range; MFD is only 11.5 feet; power zoom is great for framing/composition;It's a carry on item unless you are willing to risk checking it... not likely! Will fit in a Pelican 1510 carry on. It's a heavier lens.
Brilliant, even on digital: I highly doubt I will ever part with this lens. The FA* 250-600/5.6 is definitely better than the Sigma 500/4.5 EX DG APO lens I used. This heavier lens - like any larger super telephoto - requires top shelf tripod and gimbal head to bring out the best images. I have a Gitzo GT3541XLS, Wimberley WH-200 gimbal head and Wimberley P-50 lens plate - three screws hold the almost 7" long plate to the tripod collar foot. I've not really tried it on a monopod yet, but I now have a Wimberley C-10 QR clamp to mount on my monopod so I am looking forward to seeing it in action.reviewed October 9th, 2010
It's a fantastic lens. This is by far the better lens of choice and the MFD kicks the competition around by a good margin. Most 600/4 lenses start at 15.5 feet and go up - that's the lowest in class of any 600mm - next 600mm is 15 feet - great for shooting in a blind/hide. Only Nikon's newest 600/4 is on par with the FA* 600/4 in that aspect. Having a max. aperture of F/5.6 is but a small trade off for it's flexibility. When the light is getting that low, it's becoming a compromise anyway. All wrapped up into a unique FL zoom.
What's astounding is that the FA* 250-600/5.6 is unbelievably sharp even wide open throughout the entire FL range. The proof is in the images I have taken with it. If it's a tad soft at 600mm wide open, then that is an issue with the photographer's technique, nothing more. This is another example of the pinnacle of Pentax optical engineering mastery.