Everyone says how important a larger exit pupil will be for lowlight/night viewing, but higher powered bins with larger objectives will score a higher Twilight Factor number.
Seeing how Exit Pupil seems to decrease as the Twilight Performance increases, which is the more important factor when trying to narrow down choices between lowlight/night viewing binoculars?
I've looked at both the Pentax and Nikon websites and can find no mention of "Twilight Factor" as a specification. Can you tell us which binoc manufacturer(s) use this, and what they say it is supposed to mean?
[QUOTE=xenophobe]Everyone says how important a larger exit pupil will be for lowlight/night viewing, but higher powered bins with larger objectives will score a higher Twilight Factor number.
Seeing how Exit Pupil seems to decrease as the Twilight Performance increases, which is the more important factor when trying to narrow down choices between lowlight/night viewing binoculars?[/QUOTE]
Twilight factor is simply a mathematical equation = square root of the magnification x objective diametre. It does not say anything about the overall optical performance. A poorly made 8x40 will have the same twilight figure as a top of the range 8x40 (17.9). The same applies to the geometric light gathering figure = exit pupil diametre, squared. exit pupil measuring 4mm = GLG (16)