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Started by George Page, 11/02/2002 10:23PM
Posted 11/02/2002 10:23PM Opening Post
The exit pupil for the Kowa Highlanders is well below the recommended lowest value of 3. The exit pupil for any 82mm objective, if kept within the recommended 3 to 7 range limits the magnification to a range of 12x to 27x.

The Highlander magnifications are 21x, 32x and 50x.
Direct comparisons of these binoculars to some of the best binos on the market as well as with 4 inch apos is highly favorable in a review posted here. The reviewer is experienced and has access to the best equipment available. The predicted problems based on low exit pupil values with an 82mm objective used with such high powers seems to be incorrect.

The Astro Index of these binoculars, another useful criteria determined by multiplying the square root of the objective and the magnification, is quite high for these binoculars.

For a given objective and increasing magnification the exit pupil decreases (BAD if not within range of 3 to 7) while the Astro Index as proposed by Alan Adler, increases (The higher the better).

These binoculars seem to be rather impressive. The index pupil values at 32x and 50x would suggest problems at these magnifications but this is not supported by user experience. Since the index pupil values are used to evaluate equipment, I would appreciate any comments as to the reason this precicted problem is not evident.

It may be particularyl useful to understand and properly weight the exit pupil factor when making an evaluation, especially when the product is not readily available for inspection.

Posted 11/03/2002 06:31AM #1
The 50x per inch of objective diameter rule of thumb for relating usable magnification to objective diameter in telescopes would yield an exit pupil of approximately 0.5, and the 50x rule is often exceeded. Is there any reason(s) why this would not apply to binoculars? Guess a review of optics would shed some light on this.