photo:sigma500mmf4
Table of Contents
Sigma 500mm f/4 Ultratel mirror lens
see also:
introduction
- this super telephoto lens introduced in ? is a catadioptric mirror lens, and as with all such mirror lenses, share the following characteristics:
- manual focus
- fixed aperture (in this case f/4)
- virtual elimination of chromatic aberration as uses mirror rather than lenses
- also means focus position for infrared photography is the same as for light photography
- central mirror:
- allows much more compact lens length as the optic path is reflected internally twice
- by necessity, blocks some of the light and thus causes:
- decrease in image contrast
- characteristic “doughnut” shaped bokeh imagery in out of focus areas
specs
- 500mm focal length and field of view (5°) at infinity focus
- fixed f/4 aperture
- lens elements, ? groups
- closest focus 15m (3m via an extension tube)
- rear filter thread
- T lens mount thread
- 159mm diameter, 216mm long and 2.7kg (6lb)
- comes with a special lens cap that has a removable inner section. Leaving the lens cap in place, but removing the inner section, cuts the mirror's aperture to f/5.6
- matching 2X teleconverter
reviews
photo/sigma500mmf4.txt · Last modified: 2014/05/18 18:17 by gary1