I've owned this generally reviled mirror lens since the late 80s, when Bald Eagles began showing up again in the lower 48. Most photogs consider it a piece of junk. I read where one fellow sold his at a garage sale for $10 and felt guilty about it. Another guy simply binned his. My results with Pentax 35mm cameras were not good, and the lens had been gathering dust over the last two decades.

Mounted on a modern Pentax 10mp digital SLR, the doggy mirror has given me the occasional good result. Image quality (IQ) is quite poor, but contrast and color rendition are surprisingly good - there is almost no detectable chromatic aberration (CA). The K10D uses an APS sensor, so the 500mm mirror gives an effective focal length of something just over 775mm, all in a trim package not much bigger or heavier than your standard coffee mug. Due to the long reach and light weight, the Pentax/Cambron combo makes for a serviceable hand-held field imaging system

The K10D has an image stabilizer system that compensates for camera movement by jiggling the sensor. The great virtue of such systems is that older lenses can take advantage of the body-based shake reduction. Unfortunately, the K10's performance tails off at higher ISO settings. If only! Adding to the challenge (and rewards!), even through the K10D's very bright true pentaprism viewfinder, the Cambron mirror is extremely difficult to get into focus due to the optimistic f8 rating for the lens. It's truly a Dark Mirror

The Moon was about 45 degrees above the horizon when the sky cleared and I scraped together a few minutes to set up Velbon (video) tripod and take 20+ exposures at ISO 100 and 1/125 sec, with varying results and one keeper, which we see here reduced to 75% after some image processing in Corel PhotoPaint 10. I applied the auto-equalize filter. twiddled curves with the standard diagonal S-shape (no relation), and finished out with PhotoPaint's Unsharp filter (100%@5 pixels). I also ran the unprocessed image through Photoshop 7, but judged the results from PhotoPaint to be superior.

Thanks Raoul, for your efforts and encouragement - however unspoken - to crank up the Dark Mirror and share my results here.

S