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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

Recent content by typo

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    Review of Kowa BD II 6.5x32 XD

    Torview, That's a pretty impressive description, but probably merited from the few minutes I enjoyed with one at Birdfair. I hate tripods so usually make do with 10x, but life is just a bit more chilled with a lower power. I liked the little Kowa a lot too. David
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    - The nominal luminous power of the binoculars:

    Steve, I've already posted this in another thread but it's probably helpful to do again here. http://www.physicsinsights.org/simple_optics_brightness_1.html Those studies by Berek and Leinhos actually did have transmission as a factor, but that has largely been forgotten about over the last...
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    - The nominal luminous power of the binoculars:

    Lee, It seems that you have not understood the fundamental points debated in this thread so I'll recap on a few points. Rico claimed in #1 to have invented a formula that shows that the luminous power of a binocular changes with magnification. Totally impossible by the laws of physics. In #4...
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    New for 2020 Meopta Meopro Air Binoculars

    Thanks for the info. I really hoped this would be the year for the Meostar update, but with that price tag it might be a serious contender. Anyone going to the SHOT show? David
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    - Magnification and move vision:

    In case anyone wasn't sure about Rico's claims that 'brightness' changing with magnification there are loads of articles on the internet that state plainly that it cannot, but this one popped out first this morning. http://www.physicsinsights.org/simple_optics_brightness_1.html As for this...
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    Light transmission comparison esp. Zeiss

    I don't know where Gigs found those plots, but the first screenshot attached shows a plot of the current CIE 2006 luminosity function. The second screenshot is from Nature 26756 (2016) that shows that the spectrum of the ambient light is predominantly in the blue and violet deep into twilight...
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    Light transmission comparison esp. Zeiss

    Tom, You can download Holger's paper by clicking the link at the bottom of the introductory section here. https://www.birdforum.net/showthread.php?t=385328 What the work of Berek (in that paper) and Köhler and Leinhos indirectly shows is that the proportion of the available light reaching the...
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    - Magnification and move vision:

    Introception, Thank you for that eloquent explaination. Perhaps you will find it useful to have a look at the discussion that followed Rico's original post on this subject. https://www.birdforum.net/showthread.php?t=384516 Some of us did try to explain to Rico that 'brightness' is a human...
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    - Magnification and move vision:

    Lee, I think it's worth looking again at Rico's post again in it's entirety so we don't take this "too bright" comment out of context. "the exit pupil is not the only factor to calculate the "light power" of binoculars, but it is essential to also use the magnification value." It is really...
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    Eyepieces touching glasses?

    Roberto, Mpeace is right, your post can be read that way too. I prefer my glasses to touch the eye cups for stability. My glasses are fairly close fitting, so on most binocular models I prefer to twist out the eye cups a little. Unfortunately differen companies measure their ER in different...
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    Eyepieces touching glasses?

    Hi Roberto, I suppose I must have tried out two or three hundred different 8x and 10x binoculars with their eye cups fully down and not once have the lenses of my glasses touched those of the eye pieces. I can't say that it couldn't happen with some prescriptions, but I don't think it should be...
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    - Magnification and move vision:

    Celestron have a regular stand at the UK Birdfair and they put a bit more of their astro stuff on show a couple of years ago. I tried the 25x70 and 20x80 on tripods and the 15x70 hand held. I wouldn't have described any of them as bright, but the 20x80 was the best of the bunch. David
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    Crossfire HD

    Hello Sean, I thought by now you might have had some comments from some that have a closer look than I have. I've really only done a quick side by side with the Diamondback HD on the Vortex stand at a couple of Birdfairs and I picked up the 8x not the 10x. For what it's worth I much preferred...
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    - Magnification and move vision:

    Lee, re. #97 This is to do with Rico's magic formula for Light power. The numbers in that first series all come to about 63. So between dawn and sunset when terrestrial luminance can vary a thousand fold, and the pupil of the eye might range from less than 2mm to over 4mm, the number 63...
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    Mid-price binoculars recommendation

    SzimiS, It sounds a really unfortunate dilemma. It's never easy to see things through someone else's eyes, but there are very good binoculars out there at sub-alpha prices. It just depends on your priorities. I had considered the Monarch HD lacklustre but the samples on the stand at last...
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