Mirror / reflex lenses... well how do they get? 55mm? 100mm? 200mm?

so I'm a nut "fuzzy donuts"...

Mirror / reflex lenses... In short how do they get? 55mm? 100mm? 200mm?

I wonder why you would be interested in "short" mirror of focal length.

These lenses perform a very special purpose and you normally not wish to use one for general photography.

A lens 'mirror' (technically, these are "catadioptric" lenses which means that it uses a combination of lenses and mirrors.  The clear glass façade is a "corrective" and is technically a goal, even if the map are minor.

These lenses have no ability to communicate with the camera - they have a focal report sets which cannot be changed.  They are setting manual focus only.

They usually come in focal length of 400mm, 500mm or 800mm.

When a lens uses glass elements, the element works by bending light.  Whenever you bend light through something objective (rather than using a mirror), refracts the light based on its wavelength.  The red light does not turn blue light for example.  This means that an element simple single lens can focus all wavelengths of light for the same focal plane.   To fix this, additional lenses items are included - often SEVERAL elements of goal.

When the lenses lie, the amount of light making it to through drops - and to compensate, the lens must have a far greater physical diameter.  When using lenses, these should also be physically larger.  As the elements of lenses get fat, the Prism effect that causes the dispersion (different wavelengths of colors different amounts of curvature) becomes even more extreme.  This is why VERY long focal lengths become VERY expensive.

'Mirror' lenses avoid the problem by bouncing the light on mirrors... There is no dispersion by bouncing a light on a mirror (you are not technically passing light 'through' an objective element.  This is substantially the cost of the construction of the lens!

Mirror lenses are usually "t-mounts" and you should buy a T adapter for your camera.  As mentioned above... you can not adjust the report f / d and the lens is manual focus only.   There is no communication between the camera and lens (the camera behaves as if it had no target).

Out-of-focus image areas will be blur based on the shape of the opening... which is actually shaped donut for a mirror lens.  This means out of areas of interest have black spots in the Middle - resulting in a very unpleasant quality of out-of-focus areas.

A 800mm mirror lens could cost $200 (more or less) and you need the adaptor in T (maybe another $15-30 depending on who makes them.)  An 800mm lens actually designed for an EOS mount (with auto focus, Aperture, control etc.) would be significantly more expensive (probably in thousands).

The inability to change the focal reports, the update manual constratint and the lack of autofocus... There is a considerable handicap in terms of speed and flexibility of shooting.   No, you probably want to use as a daily goal.

Tags: Canon Camera

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