Catadioptric Lenses Have Several Drawbacks
Weighing just 25 oz., this 500mm mirror lens is ideal for nature, wildlife, and sports and photography. This features a a faster F stop of F6.3. It also includes lens caps, lens case and a 1 year Rokinon warranty.
T-Mounts are available for all the digital SLR systems, as well as for C-mount systems. However, in every case the fixed f/6.3 aperture is not communicated to the camera body. As such, you can use the lens in "M" manual exposure mode or "A" aperture-priority mode only.
This lens has a broad diameter and stocky build, making it a bit easier to handle than a normal refractor lens. It also has a much different rendering of out of focus areas than a normal lens; highlights will be doughnut-shaped rings with more saturation and contrast on the edge of the ring than on the center.
Catadioptric lenses have several drawbacks. The fact that they have a central obstruction means they cannot use an adjustable diaphragm to control light transmission. This means the lens's aperture value is fixed to the overall focal ratio of the optical system (typically f/8 for 500 mm designs, or f/11). Their modulation transfer function shows low contrast at low spatial frequencies. The folded optical path does reduce the length of the lens, but increases its width.
Their most salient characteristic is the annular shape of defocused areas of the image, giving a doughnut-shaped 'iris blur' or bokeh, caused by the shape of the entrance pupil.
Several companies made catadioptric lenses throughout the later part of the 20th century. Nikon (under the Mirror-Nikkor and later Reflex-Nikkor names) and Canon both offered several designs, such as 500 mm 1:8 and 1000 mm 1:11. Smaller companies such as Tamron also offered their own versions. Of the major manufacturers, currently only Sony (formerly Minolta) offers a 500 mm catadioptric
lens for their Alpha range of cameras.
Samyang offers a variety of uniquely priced optics, delivering a lot of optical
capability for very little money. These rebranded catadioptric lenses are
available under the names of Bower, Opteka,
Phoenix, Rokinon, Sakar,
Vivitar and others.
Mirror lenses can produce pictures and under carefully chosen conditions they
may even produce pretty good ones. However, these situations are rare and therefore
most will have unsteady background blur. Most mirror lenses suffer from a rather mediocre optical performance. This may all be fine for personal purposes and for documentation but most likely you'll not be able to sell such pictures. Therefore a classic (refractive) lens like a 400/5.6 fix-focal or even a xx-500mm zoom
or even a 70-300-f/4-5.6 with a 1.4 or 2x teleconverter is usually a better and more serious approach. Nonetheless mirrors are quite cheap
(but you get what you pay for).
(To rephrase the paragraph above: Mirror lenses are Junk!)
This lens is an ideal candidate for astrophotography use when mounted to a Vixen GP2 Photo Guider (or other motorized equatorial telescope mount).
• Fixed-aperture 500mm f/6.3 mirror lens in T-mount
• Rokinon 500mm F/6.3 Mirror Lens
• T-Mount Adapter
• Front & Rear Lens Caps
• Lens Hood
• Lens Pouch
• 1-Year Warranty
April 16, 2010
By S. Lee "JAM" (UTAH)
This review is from: Rokinon 500mm f/6.3 Multi-Coated Mirror Lens for Canon EOS 50D, 30D, 20D, 5D, 7D Digital Rebel XS, XSi, T1i & Film SLR Cameras (Electronics)
LOVE IT LOVE IT LOVE IT. DONT BELIEVE THE PEOPLE ON THE BLOGS AND REVIEWS SAYING IT IS TOO MUCH OF A HASLE. I BOUGHT IT AND HAVE FOUND IT SIMPLE TO USE (IF YOU UNDERSTAND THE BASICS OF SPEED AND ISO FOR LIGHTING CONDITIONS) JUST BUY IT AND YOU WILL LOVE IT. WHAT? YOU THINK YOU MIGHT AS WELL SAVE YOUR MONEY AND BUY A 5K LENS> YA RIGHT!!! THAT WILL NEVER HAPPEN> YOU WILL NOT REGRET THIS.