Folks, I feel that my next lens acquisition needs to be a long telephoto for wildlife. I don't have the bucks for one of the 400, 600, or 800 mm L lenses; so I've been thinking about the 500mm F8 mirror lens. It will obviously be a good bit darker, but are there other considerations? I've also read that mirror lenses in general aren't nearly as sharp as refractors. What about chromatic aberration, etc.? What about non-Canon lenses like the Sigma 600mm F8? What have your experiences been?

Thanks!

-- Mike Bechtold (Wmichaelb@aol.com), September 07, 2000

Answers

The biggest thing with the mirror lenses is that they have funny looking out of focus highlights. Due to the design, out of focus highlights show up as little donuts of light. This may be OK to you, or it may not be.

And YES, an f8 lens is going to be dark and hard to focus.

I have been thinking of getting one, but I do some aviation photography, so shooting an airplane against the sky, there should be little problem with out of focus highlights.

-- Terry Carraway (TCarraway@compuserve.com), September 09, 2000.

Mike,

My reading on mirror lenses vs. refractors was (and this is 20 -25 year old info) that mirror lenses didn't suffer from color fringing ( I think the term is chromatic abberation ). Reason being that light paths for different colors are the same when reflected from a surface. When they are refracted through a lens red, green and blue focus at different points, degrading the image. Many modern teles are designed with superior glasses and are sold as apo-chromatic, eliminating the color fringing effect. I bought a brand new 500mm f-8 Canon FD lens in Singapore 2 years ago. I haven't done any really critical work to say that it's good or bad or indifferent, but I am pleased with the prints and slides I've made with it. Terry Carraway's comments about donut shaped highlight's do apply. They are most noticeable in boat or surfing situations with lots of little reflections of the sun off ripples in the water's surface.

-- Bill Salati (wsalati@powwowmail.com), September 09, 2000.

Hi Mike,

I have only two days' experience with a genuine FD 500mm mirror lens, but here goes. Everybody loves an "expert." The f/8 fixed aperture makes it considerably more difficult to focus than my 400mm f/4.5. Without the vari-pitch cam like the 400, the actual focusing mechanics are more touchy as well. I have no images on film yet, but the viewfinder image seems sharp using the tripod. I had borrowed a nameless 500 mirror a few years back, which produced slightly soft focus and poor contrast. I think the Canon will be sharper and have better contrast and color saturation. The FD 400/4.5 is beautiful-- surgically sharp, excellent contrast. Makes just beautiful slides. The mirror lens is vastly lighter and more portable. Out-of- focus "donuts" show up even in unexpected places. Tree leaves even create subtle ones. That phenomenon also shows up in other ways. An electric pole takes on a faint multiple image when out of focus. Canon literature does say, as mentioned in previous responses, that chromatic aberration doesn't exist with the mirror. Like you say, though, my 500 cost less than 1/4 of what I paid for the 400! Bottom line opinion: if viewfinder brightness is OK for you to focus, it is a real option for an entry into super telephoto.

-- Alan Swartz (swartz@tyler.net), September 18, 2000.