Thanks for your comments Henryk and Todd,

Looks like we three agree on not using *dark* sunglasses!

Cheers,

Jim Kelly


"Henryk Birecki" wrote in message
...
| Jim,
|
| there is a big misconception in what you wrote. For polaroids to be
| polarizing they have to absorb 50% of light, and then there are more
| efficiency losses. Sun Tigers are about 50% or more transparent
| (integrated intensity) so are likely to be "brighter" than
polaroids.
|
| In addition to spherical aberrations that you refer to talking about
| depth of focus there is also chromatic one. Suntigers shrink the
| optical bandwidth effectively reducing chromatic aberration.
|
| Using Polaroid glasses and liguid crystal displays is another trick
to
| be mastered as the latter also rely on polarized light.
|
| Cheers,
|
| Henryk Birecki
|
| "Jim Kelly" wrote:
|
| * a dark colour simply causes the eye to open wider to let in an
| appropriate 'amount' of light. When opened wide the eye is very
| susceptible to stray light coming from the side of the lenses, and
the
| depth-of-field is dramatically reduced. Keeping the eye small
ensures
| that maps, instruments and long distance focussing are likely to be
| much easier.
|
|