Thanks very much for the offer! Can't make it until after hunting season, though, which looks like it will extend into January for me this year.
<br>
<br>You brightness testing system sounds interesting, but according to all the optical engineers I've consulted, photopgraphic light meters don't work very well for telescope brightness tests. The big problem is their small field. If held close to the ocular lens, you're only testing the brightness through the center of the optical system, not overall brightness. If held farther back, at the apex of the exit pupil, ambient light from the side interferes with the reading.
<br>
<br>In optics labs they use a different setup, a big sphere painted white inside and lit very brightly, called an integrated or intergrating sphere. The objective of the scope to be tested is inserted into a close-fitting tube in the side of the sphere, and a wide-lens meter fits tightly on the ocular end.
<br>
<br>The light entering the scope is extremely consistent, and all the light leaving the scope is measured without interference from outside light. Have observed these are both Leupold and Zeiss labs, and they will measure transmitted light down to a tenth of a percent. But they're a little out of the economic reach of the average gun writer!
<br>
<br>Actually, proving that 30mm tubes don't transmit more light was simple. The theory promoted by some people(primarily salesmen) is that the bigger tube allows the use of bigger lenses, which allow more light through the scope. The flip side, of course, is that a 1" tube somehow reduces the light, through mechanical constriction.
<br>
<br>If this theory were true, the exit pupil of 30mm scopes would be bigger. This is easily tested by measuring the exit pupils of two scopes of the same magnification and objective-lens diameter. I did this with several pairs of similar scopes, and found that the exit pupil was exactly the same at the higher magnfications, regardless of whether the scope had a 30mm or 1" tube.
<br>
<br>Only at magnifications under about 5x (depending on objective diameter) did the 1" tube constrict the exit pupil. At those magnfications, however, the exit pupil was typically at least 8mm in diameter, even in 1" scopes, more than the human eye can use. So there is no optical advantage in 30mm tubes.
<br>
<br>Tests in integrated spheres bear this out. The only real advantage of a 30mm tube is a greater range of scope adjustment--but only lenses for 1" scopes are used. Several of the 30mm scopes on today's market use larger lenses, and have even less adjustment range than 1" scopes from the same companies.
<br>
<br>We seem to have strayed from muzzle flash into optics!
<br>
<br>
<br>
<br>
