Opteka 500mm f/8 T-Mount Telephoto

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For those considering a 500mm "mirror" lens, I highly suggest checking these instead.  There's several brands currently available  which usually sell for around $120.00. They come with a tripod mount, and use a four element design. While not up to the high quality, or speed of more expensive brands, they'll give reasonable results if properly used.

 Compared to the same millimeter mirror lenses, these offer smoother bokeh, brighter color, and have an ajustable aperture. They also use a T-Mount adapter allowing fitting to most bodies. Though larger than mirror lenses, they weight 22.6 oz., less than best closest focus distance of  33 feet, but angle of view is a tight 5 degrees.

Lacking coupling, it's necessary to shot in manual, or apterture priority. They're best in bright sunlight, and used with mid to higher ISO ranges due the f/8 aperture. Since coatings are minimul, a UV filter is highly recommended. Purchase models having a 67mm filter size, as these are the sharpest models available.  Sample photos:

Photo taken "hand held" in cloudy conditions, ISO 800 f/8. One click of sharpen in PhotoShop with color adjustments. This lens seems to have a slight color cast, but  adjustment in post processing will easily correct it. Since coatings are minimul, I also suggest avoid shooting toward the sun to avoid lens flare.

These are  excellent for those who can not afford more expensive  telephotos, and certainly usable in proper conditions. I wouldn't recommend it for shooting fast moving sports figures, but for general photography it performs reasonably well.

For this lens to perfom it's best, stay at 1/750th of a second or above, or mount to a stable tripod. If light permits, stopping down one, or two f/stops always increases sharpness of any lens. Using a shutter speed which is too slow, is often mistaken for bad optics. As a general rule, it's necessary to keep shutter speed at least 1.5 times faster than the lenses millimeter to avoid motion blur.

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