BirdForum is the net's largest birding community dedicated to wild birds and birding, and is absolutely FREE!

Register for an account to take part in lively discussions in the forum, post your pictures in the gallery and more.

Reply to thread

Message: <blockquote data-quote="denco@comcast.n" data-source="post: 1558231" data-attributes="member: 25300">"That said though with modern AR, dielectric mirror and phase coatings there is little effective difference between the two in terms of transmission but roof prism components are more expensive to make because they have to be made to higher tolerances or require additional coatings."     Well said but not true in actual light transmission testing. In some government testing for light transmission in binoculars some $200.00 porro prisms outperformed the Alpha roofs. Sadly even the Steiner 7x50 Marine and Tasco Waterproof 322BW had better light transmission than the Swarovski and Zeiss (96.4% and 95%). The best performing roofs were the Zeiss FL 10x56 and the Swarovski SL 10x50 at 93.3% light transmission while some porros like the Nikon Prostar were at 97.5% light transmission. It is a fact that porros are more efficient at transmitting light. Nikon 8x32 SE's are as bright as a lot of 8x42 roofs. Here is a link to the summation of the article.<a href="http://www.photography-equipment.org/lens_light_transmission_efficiency_vs_brightness_63770.htm" target="_blank">http://www.photography-equipment.org/lens_light_transmission_efficiency_vs_brightness_63770.htm</a>Dennis</blockquote>