Didymium (1 Viewer)

Contrary to expectations, I have found that the stated eye relief of Zeiss binoculars is sufficient for me to use them. I have found that the colours appear to me, on some models, to be more natural than, say, my Swarovskis. This appears to be particularly the case with older models.

By "natural", I mean closer to what I perceive through my spectacles.

I like this. I am bothered by what might be termed the photoshopped interpretation, as one binocular retailer I spoke with, characterized it. Over-saturated could be another apt adjective. Others appear to use the word "pop", amongst others.

Holger Merlitz has written: "Since that time," the 1970s "the color saturation of the image reached that high level we are used to find with modern optics." (http://www.holgermerlitz.de/wisdoms.html). I sense some criticism in that statement, possibly wrongly!

Allbinos writes of the Swarovski 8.5x42 Swarovision under Pros, that it has "very good colours rendering". The transmission chart where the the transmission is fairly level from the blue end rising gently to the reds, may explain this. But, to me the colours can be over saturated to my eyes. The Swarovski EL 8x32 WB is also stated to have high scores for color rendition, but I have not looked through one.

It seems that the emphasis on the red end of the spectrum might have similarities to the red enhancing Didymium filter that I used in my film days, for Didymium photographic filters are/were often used to enhance autumn scenery by making leaves appear more vibrant. Apparently it does this by removing part of the orange region of the color spectrum, acting as an optical band-stop filter (Wikipedia).

I wonder if Didymium is used in binocular glass or coatings, and other techniques to achieve high saturation levels?

This is but my guesstimation. The manufacturers strive to avoid additives that cause transmission loss or skewed colours (which is basically the same, reduced transmission can influence more or less of the spectrum, when it's a slightly narrower band or a sloped transmision curve, colour bias can be detected)

Once the key optical elements are chosen, measures must be taken to adjust colour bias to the desired style.
This is done by designing the properties of each and every single lens's and prism's antireflective or reflective coating.

Using dielectric mirror surfaces allows for a higher overall transmission rate, but I suspect it can also cause uneven curves or some narrow colour bands considerably darkened. This must in turn be adjusted with the antireflective coating's properties.

Exactly what's in (for example) Nikon's ED glass is unknown to me. I adore the vibrant but still perfectly natural colours of my Fieldscopes and the EDG binocular I own. Before that, I had a HG L that took it a bit too far for my taste. The Zeiss FL I owned at the same time was its opposite with a bright, but slightly palish view.

//L