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Message: <blockquote data-quote="denco@comcast.n" data-source="post: 3642811" data-attributes="member: 25300">The HT is not on that list. I was just using that as an example of the relatively higher transmission values of porro's compared to roofs. The main point I was trying to make is as EdZ says is:"While this is by no means an exhaust sampling, of the comparable roofs and porros that I've measured, porros generally have not only higher transmission, but also better illumination. "I find it hard to believe  houseofoutdoor.com's transmission's values on the SE of 85%. I have compared the Habicht 8x30, Nikon 8x32 SE and Nikon 8x30 EII  and houseofoutdoor.com has a transmission of 95%, 85% and 75% respectively for each and I don't really see a 20% difference in transmission between the Habicht and the Nikon 8x30 EII. Here is Allbino's methodology in measuring transmission.TRANSMISSION (15 points) - Currently we use spectophotometer to obtain the transmission graph in the range of wavelenghts from 380 to 900 nm. The method is very precise one and allows us to minimalize uncertainties to around 1%. In older tests we used three less accurate methods:We mount a high level digital camera to an eyepiece (ocular lens) and we take a picture of diode. Then after standard procedure of data reduction, we carry out aperture photometry by comparing diode brightnesses (measured by eyepiece + camera configuration). Results depend only on lens diameter (which we know) and light transmission (which we can count).We mount a high class CCTV video camera and record diverse luminosity star clusters (for example ‘Pleiades’) on a very starlit sky. The differences in range results from different transmission.Another method rests on projecting intensive sunlight onto shaded white screen. A part of this screen is directly sunlit and to shaded part we glue a ruler. The screen is located in a specific distance to line up and cover screen surface brightness with projected image of sunlight surface brightness. Now we take a picture of this projected image of sun by camera. The ruler let us measure the scale of taken picture. A proportion of measured sun image in relation to actual lens area gives us the transmission.How do we test binoculars? - Description of test methods and categories.By doing many measurements and using independent methods, we estimate the precision of transmission estimate in range of 3-5%.</blockquote>

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