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Message: <blockquote data-quote="ksbird/foxranch" data-source="post: 1306499" data-attributes="member: 37413">Kevin perhaps I am not understanding your definition of "one frequency", which I thought referred to One Frequency of Light. I am specifically commenting on this quote from your most recent post "So my working hypothesis is you arrange the films to preferentially reflect one the polarizations at the lower interface and allow the "leading" polarization through the interface. Then you propagate that through the film reflect it from a outermost interface then propagating through the film again (so being delayed) until it meets back up with the other polarization and now they're both in phase. I suspect there is an extra (non-obvious) trick that requires three layers but I suspect it has something to do with selecting the polarization. When you do this you can get the phase delay to zero at one frequency"Since there are an Infinite number of visible light frequencies visible across the full spectrum of our ability to see, and at most, companies like Zeiss might be compensating for the s and p phase incoherence at 20-30 of these frequencies, 99+% of the light frequencies coming into the light path and reaching the eye are not coherent. The Zeiss compensation in their roofers might be better than other roofers, but it is still at least 100x worse than a well made porro.I never got an answer on this but why is it that the best images for birding seem to be produced by the Nikon SE series bins (porros) (or possibly the Fujinon FMT series)? If Nikon can make the most highly rated bins image-wise, it is surprising that they don't make the same objective and eyepieces for a roofer, unless this would show up the obvious inferiority of roofers due to phase incoherence.I offered the advantages that most porros offer and they seemed very important (wider fields generally, much lower cost for the #1 rated bin image-wise according to reviewers, which is the Nikon SE porro system, etc.). You said there was a similar phase incoherence problem in porros but never defined how it would work when the light path enters or reflects through porro prisms at 180 degrees or 90 degrees and any other light reflections do not continue in the light path, they either reflect back out of the binocular, or are disbursed or reflected into baffles or blackened-frosted prism sides. When the offending out-of-phase light waves doesn't get to your eye there isn't a phase coherence problem.Leica created all the misunderstanding/marketing-effect about roofers with their early Trinovids. This mis-perception in the market has continued to this day and in much the same way that we lost about 90 years of electric car development when we didn't support the early electric cars, the world's largest binocular markets got swept up into the huge mis-perception that just because roof prism binoculars were more expensive (like the early Trinovids), they had to be able to produce a better visual image, which is patently untrue (like the notably "soft" images produced by the early Trinovids). For years the US military has been hoping there was some kind of straight-line design binocular (like a roof prism design binocular) that can produce as sharp of an image as a porro prism binocular, because roofers might be easier to make waterproof, and they could be easier to make rugged, and they could be easier for soldiers to transport. But no roof prism binocular has passed the minimum standard for sharpness (to know the enemy, you must be able to ID the enemy). Right now Fujinon makes US military binoculars using their flat field designs. Other companies are close, but all the competitors end up being porros because they produce the best visual images. The older East German 7x40 porro prism military binocular is still in great demand and 90% of all the designs now made after testing for most military are prorro prism designs. Sure the Bundeswehr buys some roof prism bins, but only under duress due to the importance of Zeiss, and Zeiss' unwillingness to make porros for the military for "marketing confusion" reasons (in other words if Zeiss made a great porro prism bin for the German military, consumers would want to get them in a CF design and this would make Zeiss roofers look bad). It's the same reason Nikon won't make a waterproof version of the SE series.</blockquote>

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