Re: Color contrast at the night sky?


Brian Tung schrieb:



1. (a) One pair of binoculars shows better color contrast in full
daylight than the other pair. (b) On the other hand, the second
pair shows better color contrast in twilight than the first pair.

2. (a) One pair of binoculars shows more detail in DSOs than the
other pair. (b) But this other pair shows more detail on
terrestrial objects than the first pair.

And finally, you're saying that 1a and 2a are the same, and 1b and 2b
are the same (and also has a yellow cast). Is that all correct?

Yes, this is exactly what I mean.


If that's what you mean, my guess is that the (b) binoculars are acting
as a weak color filter, and this often has the effect of sharpening
some detail when the objects are easily seen. However, this filtering
also reduces the total amount of light that gets to your eyes, making
dim objects (such as DSOs) harder to see, which is why (a) is better for
those nighttime observations. But it's hard to say for sure without
more observations or first-hand inspection of the binoculars.


I´m talking here about some binoculars of very high quality. I took
also different color plates and charts which are used normaly for photo
objectives inspection. I found that the (a) binoculars (Leica Ultravid)
showed all colors more vividly and stronger but the (b) binoculars
became superior when I watched at a grey tone chart. I think that the
(b) binoculars made by Swarovski have a light transmission with a
maximum shifted slighted to the the yellow range of the visible
spectrum of light. Finally this may work like a filter even though the
transmission as a whole is pretty high and close up to 90%.

Steve

.

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