The Reflex Lens
August 11, 2015 by rodsager (originally posted today on ‘Couv’ Camera)
In the 1980s, reflex lenses became very popular among amateur photographers. Reflex is a bit of a slang term for catadioptric lenses that use a Cassegrain design originally invented for telescopes. First off, forgive some of my slightly soft images here. I hand-held some of the photos under overcast skies and a slight breeze. Reflex or “mirror” lenses are not known for extreme sharpness anyway. The idea behind the lens was to create a long focal length telephoto lens that was small and compact. In this regard the design is nothing short of brilliant. I still own my 1980s Tamron SP 500/8. Tamron made one of the best 35mm cat lenses. The Tamron lens is very small as you can see held in my hand in the photo. This is a 500mm lens!
Reflex lenses have some interesting characteristics that can be both derogatory and beneficial depending on your perspective. First the aforementioned lack of absolute resolution. I am a bit of a sharpness freak, but this Tamron lens is not “soft” by comparison to other cats in fact the opposite is true; it is soft by nature. It just won’t resolve as well as a traditional lens design. Another issue is that these types of lenses have no aperture diaphragm. The lens is always ‘wide open’. There is no stopping down for extra depth or sharpness. That said this 500mm lens is 1/4 the length and likely 1/2 the weight of a similar 500mm traditional lens.
Read the rest here ‘Couv’ Camera…