Hopefully, this short review will help others who are interested in P67 telephotos. Overall construction and finish of this lens is outstanding. The first thing you'll notice about this monster is that it makes the 300mm seem like a toy. It weighes about 13 lbs. It is hard to handle/carry and to set up on a tripod. It will only accommodate a 1/4 inch tripod screw but I feel it needed a 3/8 inch type. Pentax recommends using one tripod on the lens and one on the camera body. This proves to be extremely difficult when you need to change focus or framing. I suggest using one large tripod with locked mirror and cable release. The diaphram and aperture ring are the finest I've used on any lens. The diaphram is a twelve blade type which is a benefit because it reduces the amount of diffraction due to it being closer to a circular shape. Quarter stop settings are easily possible with the aperture ring. There is a learning curve involved when attaching the camera to this lens. It is not a quick operation. Also, if you don't tighten the ring snugly, your meter may not work (that is if you have an in-camera meter). Optical performance is outstanding especially at f/16. It is similar to the new version 200mm except not quite as sharp at f/4. Close focusing is at 38' and requires an extension tube for small subjects. Metering is manual but I didn't find this to be a problem. The 600 is an excellent lens but a challenge to use.

-- Steve Rasmussen (srasmuss@flash.net), February 21, 1998

Answers

Reinhard: The 600mm at f/4 is sharper than most refractor telescopes,mostly because the 600 has more degrees of freedom (more optical surfaces to correct aberrations). Although I have only shot this lens wide open a few times, the results have proven better than my other telephotos shot wide open. The 600 is definately well corrected. I would not hesitate to use it at f/4 for astrophotographs. The contrast is very good and easily better than their 300mm f/4. You can see the difference in the finder! SR

-- Steve Rasmussen (srasmuss@flash.net), February 27, 1998.

Gary: please see my post under P67 Optics. SR

-- Steve Rasmussen (srasmuss@flash.net), February 28, 1998.

I just finished a short lens test on the 600mm to verify the sharpness/unsharpness by using a test chart. I only checked two settings, f/4 and f/45. At f/4, the sharpness near the optical axis was quite good but the marginal areas were quite soft viewed with a 4x Rodenstock aspheric loupe. At f/45 there was a slight improvement in the center area but a huge improvement in the marginal areas. My conclusion is that this lens is not as sharp as I had originally thought at f/4.

-- Steve Rasmussen (srasmuss@flash.net), April 28, 1998.

I do a lot of astrophotography and I+m searching for a bigger tele-lens with big aperture. How sharp is the 600/f4 used full open, what about the contrast. If I have to stop down the lens, there are other possibilities

-- Reinhard Becker (becker@astro.uni-tuebingen.de), February 27, 1998.

What about the lowly (and lonely) 800ED? Do you have any experience with this lens? Please advise.

-- Gary M. Younkin (yf92525@navix.net), February 28, 1998.