Objective coating Changes (1 Viewer)

[Tobias Mennle]

Yes, they are. But COLORS mean nothing. AR coatings have no COLOR. What is seen as COLOR is the wavelength being reflected. 🐱

Bill

Of course you are right, because the full argument needs a 180 degree twist to be comprehensible. The colour that is reflected by the coating is definitely strongly reduced in the transmission curve, so the colour cast is "opposite" on a colour wheel. Colour wheel is the handy interface in the postproduction of imagery. Classic case is old Swarovski "Blaubelag" in my 1961 Habicht which shows strong blue and magenta reflections - and only that. That means, transmission curve is skewed towards yellow and green, resulting in yellowgreen, which is exactly what I saw when photographing colour casts through the binocular.

This still applies to the latest Swarovski SLC, or Leica Geovid, albeit with more subtlety. The effect is stunning though. Dedicated hunting glasses need it.

 

[Tringa45]

Of course you are right, because the full argument needs a 180 degree twist to be comprehensible. The colour that is reflected by the coating is definitely strongly reduced in the transmission curve, so the colour cast is "opposite" on a colour wheel. Colour wheel is the handy interface in the postproduction of imagery. Classic case is old Swarovski "Blaubelag" in my 1961 Habicht which shows strong blue and magenta reflections - and only that. That means, transmission curve is skewed towards yellow and green, resulting in yellowgreen, which is exactly what I saw when photographing colour casts through the binocular.

This still applies to the latest Swarovski SLC, or Leica Geovid, albeit with more subtlety. The effect is stunning though. Dedicated hunting glasses need it.

Tobias,

You have taken over 13 months to reply to Bill and he is unfortunately not posting at the moment.
As I mentioned in post #19, coatings on premium manufacturers' products are often tailored to the refractive indices of the elements to which they are applied. If the same coatings were appled throughout they would result in different reflections on different glass sorts.
Are you seriously suggesting that the colour balance of the reflections from the objectives (0,2%?) result in a complementary colour bias seen at the eyepieces?

John

 

[Tobias Mennle]

Tobias,

You have taken over 13 months to reply to Bill and he is unfortunately not posting at the moment.
As I mentioned in post #19, coatings on premium manufacturers' products are often tailored to the refractive indices of the elements to which they are applied. If the same coatings were appled throughout they would result in different reflections on different glass sorts.
Are you seriously suggesting that the colour balance of the reflections from the objectives (0,2%?) result in a complementary colour bias seen at the eyepieces?

John

John, I totally believe you that manufacturers do need to balance glass properties with different coatings, and even to accommodate for different batches of the same glass, which must be a royal pain. The latter I take from cinematography forums, because when a set of prime lenses does not have a fully consistent colour reproduction due to different batches it costs money in postproduction.

Bill wrote above "As for as I am concerned, “ruby coatings” were designed to con the unwary.". Those coatings are a good example, I saw them in cheapest Chinese glass used by my Russian friend. Colour cast is strong green, for "perceptual contrast and brightness boost" (my term). That is, no matter how bad the optical system is, the coatings "con the unwary" with the impression that the glass is much sharper and brighter than it is. Zeiss is using a similar approach, which I find not acceptable for glasses that are advertised for nature observation. Swarovski at least gives you a good choice with their different lines (they used to advertise the SLCs as "contrast optimized").

But yes, I do believe the objective lens coatings often give a good hint - not the full story - of what to expect from the colour reproduction, and using the colour wheel as a guide. Best example are the often high intensity magenta/tobacco "hunting" coatings from Zeiss and Swaro, which Leica from what I have seen only uses in the Geovids - dedicated hunting glasses - or the classic Swaro Blaubelag. I have tried to photograph colour casts in binoculars a couple of years ago.

I also believe the front lens is the most essential lens for coatings to work, at least in flare suppression.

I might want to make a list of questions regarding transmission curves and colour to hand it at least to Swarovski, so if you have input, please. Maybe it would be worth a new post.

 

[Tringa45]

John, I totally believe you that manufacturers do need to balance glass properties with different coatings, and even to accommodate for different batches of the same glass, which must be a royal pain. The latter I take from cinematography forums, because when a set of prime lenses does not have a fully consistent colour reproduction due to different batches it costs money in postproduction.

Bill wrote above "As for as I am concerned, “ruby coatings” were designed to con the unwary.". Those coatings are a good example, I saw them in cheapest Chinese glass used by my Russian friend. Colour cast is strong green, for "perceptual contrast and brightness boost" (my term). That is, no matter how bad the optical system is, the coatings "con the unwary" with the impression that the glass is much sharper and brighter than it is. Zeiss is using a similar approach, which I find not acceptable for glasses that are advertised for nature observation. Swarovski at least gives you a good choice with their different lines (they used to advertise the SLCs as "contrast optimized").

But yes, I do believe the objective lens coatings often give a good hint - not the full story - of what to expect from the colour reproduction, and using the colour wheel as a guide. Best example are the often high intensity magenta/tobacco "hunting" coatings from Zeiss and Swaro, which Leica from what I have seen only uses in the Geovids - dedicated hunting glasses - or the classic Swaro Blaubelag. I have tried to photograph colour casts in binoculars a couple of years ago.

I also believe the front lens is the most essential lens for coatings to work, at least in flare suppression.

I might want to make a list of questions regarding transmission curves and colour to hand it at least to Swarovski, so if you have input, please. Maybe it would be worth a new post.

Tobias,
I know next to nothing about cinematography but belive your prime lenses have T-stops, which are calibrated to the transmission of the of the individual lenses, whereas f-stops have openings dimensionally related to the lens' focal length.
Perhaps manufacturers of cinematography lenses can allow themselves the luxury of sacrificing transmission by using glass sorts with specific absorption properties in the interests of colour balance. This would be apparent to some cinema visitors but binocular users would prioritize transmission over minor deviations in colour balance.
Schott's introduction of HT versions of existing optical glasses a few years ago created a lot of interest although the transmission gains were very minimal at the blue end of the spectrum.
I believe that mirror coatings on Schmidt-Pechan prisms could play a role in colour balance. Porro binoculars and roof prism binoculars with Abbe-König prisms rely on total internal reflection and show a gentle decline in transmission into the infra-red. Some Swarovskis with SP prisms and dielectric coatings on the other hand have a precipitous drop above 650 nm. It's well known that Meopta still use silver coatings on the Meostars, possibly combined with a few dielectric layers between prism and siver layer to improve blue reflectivity. Could this combination explain the extended red transmission of Leica binoculars? Somehow though, I don't think they'r going to let us know.
Maybe the transmission at the objective surfaces differs slightly due to hydrophobic or hard protective coatings, but I don't think it affects flare much. Henry Link stresses the importance if internal baffling and it can also be reduced by shielding (lens hood or matte box) as demonstrated in my primitive comparisons here: Veiling Glare Comparisons.

John