OK, objective diameter divided by magnification equals exit pupil. Increasing optics exit pupil increases low light capability up to the point where it equals or exceeds that of the user – 7mm for young, healthy eyes, somewhat less at my age. However, evidently better lense and lense coating technology gives better low light capability in optics with equal exit pupil size. Hence I’m told Zeiss or Swarovski trumps Leupold with equal exit pupils.

My question – will an exit pupil greater than 7mm help overcome lesser lense coating technology – i.e. would a 6x56 Luepold give low light capability similar to a 6x42 Zeiss?

Brazos_Jack

Short answer is no.
Glass/coatings determine light that passes through the scope to the user's eyes. Generally speaking, great glass and coatings allow for a higher % of light allowed to pass. That costs money. Zeiss Victories trump Leupold scopes, regardelss of objective size, except for Leupold's VX-7, which is close to the Zeiss and Swarovski's, but doesn't equal those excellent optics. I have a VX-7 in 1.5-5x which is good, just a notch below Swaro's high end scope in the same power range.

No. Exceeding the pupil dialation of the eye does nothing to increase the brightness of the image. It does increase the latitude of the placement of the pupil (eye placement) slightly, making it easier to acquire the sight picture.

The difference in the "brightness" of two scopes of equal magnification and exit pupil size could be the difference in the light efficiency of the lenses (a function of lens quality and coatings), or in the NUMBER of lenses. Since some light is "lost" at each lens, a system which uses fewer lenses (i.e. a fixed power as opposed to a variable) is a bit more efficient in transmitting light.

However, regarding "brightness", the human eye is more sensative to certain colors than to others, and can perceive images where the colors are shifted from true color as being "brighter". The real measurment of a scope's optical performance is in its resolution. When testing for efficiency of light transmission, only a light meter can discriminate between the very minor differences on most scopes. If judging a scopes optics by human eye, the only dependable test is to use a resolution target at a known yardage. This will tell you what you need to know. Some scopes produce a "pretty" image (to your eye), while others produce a "clear" image. Use a resolution target to figure out which is which.