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Dielectric and Phase Coatings - do they interrelate? (1 Viewer)

Prime HD

I checked the Prime HD according to test:

As cited by Gijs in post #3:

-1- binocular without P-coating: the pupil of the binocular appears brighter between crossed polarizers than between parallel polarizers.
-2- binocular with P-coating: the pupil of the binocular appears darker between crossed polarizers than between parallel polarizers.

The Prime HD showed results similar to number 2. It had two "darkest positions". One with the roof line horisontally and one with the roof line vertically when looking at the lcd-screen with crossed polarizers.
Both halves had the same dark blue colour.

When looking at the screen with paralell polarizers, I could turn the bin full 360 degrees with no particular difference in the bright image....

Anders
 
John Russell said:
Dielectric coatings are today a "must have" for any bins with Schmidt-Pechan prisms but perhaps they are not without their disadvantages.

John
Click to expand...

Hi,

Out of my own personal curiosity could I ask why dielectric coatings are perceived to be a "must have"?
As stated, Meopta binoculars do not have dielectric coatings on the Schmidt-Pechan prisms, but I would be hard pressed to find a large group of binocular users who felt that the optical quality of the MeoStar B1 series is severly lacking when compared to other top-end manufactuers.
The discussions here have been great to read and the back-and-forth is really interesting, so your feedback on this issue is appreciated.

Thanks!
 
I'll have a go.

I'm sure you appreciate that the relative reflectance of silver coated mirrors is comparatively poor at the blue end of the spectrum. Dielectric coatings can (if not always do) deliver a more neutral reflected spectrum. Many here feel that for birding in particular a completely neutral colour balance is desirable and favour binoculars that are closest to that ideal. I sit on the fence on this matter. I'm not sure the Meopta reputation for a 'yellow' view is justified these days, but in certain situations I find any blue deficiency to be quite noticeable. Under the reddish skies of sunset, I find switching from my warm biased daytime pair to my bluer balanced dielectric binoculars makes a big difference to my appreciation of colours. The flip side to that is that daytime haze is mostly scattered blue light so my pairs with a warmer balance do provide a crisper more contrasty view, particularly at distance.

I think it is well known, if occasionally forgotten, that different transmission profiles are suited to different applications, birding, hunting, military, nautical etc. and the challenge for manufacturers is to find a satisfactory common denominator or like Steiner for example tweak the profiles for different markets. Certainly there is a current fashion for dielectric coatings (which Meopta offer on their component products) and many here feel it would benefit your products. I don't know if it is quite that simple. I think the HD is very good already and would be happy if it was rolled out to other models.

David
 
Last edited:
typo said:
I'll have a go.

I'm sure you appreciate that the relative reflectance of silver coated mirrors is comparatively poor at the blue end of the spectrum. Dielectric coatings can (if not always do) deliver a more neutral reflected spectrum. Many here feel that for birding in particular a completely neutral colour balance is desirable and favour binoculars that are closest to that ideal. I sit on the fence on this matter. I'm not sure the Meopta reputation for a 'yellow' view is justified these days, but in certain situations I find any blue deficiency to be quite noticeable. Under the reddish skies of sunset, I find switching from my warm biased daytime pair to my bluer balanced dielectric binoculars makes a big difference to my appreciation of colours. The flip side to that is that daytime haze is mostly scattered blue light so my pairs with a warmer balance do provide a crisper more contrasty view, particularly at distance.

I think it is well known, if occasionally forgotten, that different transmission profiles are suited to different applications, birding, hunting, military, nautical etc. and the challenge for manufacturers is to find a satisfactory common denominator or like Steiner for example tweak the profiles for different markets. Certainly there is a current fashion for dielectric coatings (which Meopta offer on their component products) and many here feel it would benefit your products. I don't know if it is quite that simple. I think the HD is very good already and would be happy if it was rolled out to other models.

David
Click to expand...

Thanks for the feedback! That is along the lines of what I was expecting.
So then the simple answer to why MeoStar binoculars do not have dielectric coatings is that the line was designed and calculated optically with the silver coated SP prisms and any change to that is considered for a new "generation" of completely re-designed binoculars, not as an upgrade to the existing series. The inclusion of HD optics is something we can do without dramatic changes to the optical / mechanical foundations of the current models.
 
MeoptaMan,

That is an interesting point. So, the introduction of ED glass in the Meostar line of binoculars does not require an entire redesign to the binocular but the introduction of dielectric coatings would?

Hmm, interesting. I would assume that stance is something specific to just the Meostar line of binoculars. The reason I say that is because I am aware of at least one series of binoculars that switched from silver to dielectric coatings without any notable change in the optical system of that binocular. Common sense would dictate that since one company was able to do it with that particular model then Meopta should be able to do it with the Meostar lineup.

However, common sense fails in this case as there may be something specific to the optical design of the Meostar that does not allow this. I would assume it is something more specific than just the lack of compatibility between the ion-assisted antireflective coatings and a dielectric coating? The reason I say this is because I have used/owned some models with dielectric coatings that weren't as impressive optically as their silver coated counterparts. My hypothesis was that the specific combination of antireflective coatings and dielectric prism coatings didn't "mix" too well.

Any further comments on this issue would be appreciated.
 
FrankD,

I probably had the wrong choice of words...I do not know for 100% if the switch from silver to dielectric coatings require a complicated optical change....something would need to be changd, but I do not know exactly what.
Better said, the switch from silver to dielectric coatings is something we would consider as part of a larger re-design; upgrade of optics, mechanics, coatings, ergonomics, etc... as part of a new generation of binoculars.
The step up from standard to HD optics was more driven by a specific OEM demand than an internal strategy.
Generally, when we upgrade the product it is preferred to be as part of a larger whole scale improvement, not incremental.
Obviously the switch to HD lenses was outside of this strategy.
 
Dear all,
The reflection efficiency from metal mirrors like silver or aluminium is wavelenght dependent. The reflection efficiency drops fast below 400 nm but the wavelenght region below 400 nm is not very important for our vision. More important may be that the reflection efficiency of all metal mirrors from 400 -800 nm or even higher are about 95% (my estimation from published efficiency curves). As a consequence of this lower reflection efficiency the amount of light which leaves the binocular is lower than in the case of 100% reflection efficiency. Using di-electric material as a high reflective mirror ( many stacks of di-electric material arre applied) two things can be regulated:
-1- the surface mirror has now a reflection efficiency of almost 100%, which gives the binocular a brighter image since more light leaves the binocular and
-2- by playing with different dielectric media and stacking the different layers the designer may be able to play with the reflection color balance.
Silver mirrors are nowadays often protected with silicium oxide layers or other hard material, so the risk of oxidation is much lower.
Further reading: Optics Source Book, Sybil Parker, ed, MGraw-Hill Book Company.
Gijs
 
Thanks MeoptaMan for joining our discussion. It's great to get information from the source.

I suspect that neither ED glass nor dielectric coatings require significant optical layout redesigns. An ED based objective would likely have slightly different curvatures and thickness but would still fit in the lens same mounting with no modification.

Leica added dielectric coatings with the introduction of the Ultravid, and ED glass with the Ultravid HD. But the optical layout seems unchanged since the Trinovid BA and BN. Field of view, field correction, eye relief and overall length are no different. This is a design that has been milked for all it's worth!

Ron
 
MeoptaMan said:
FrankD,

I probably had the wrong choice of words...I do not know for 100% if the switch from silver to dielectric coatings require a complicated optical change....something would need to be changd, but I do not know exactly what.
Better said, the switch from silver to dielectric coatings is something we would consider as part of a larger re-design; upgrade of optics, mechanics, coatings, ergonomics, etc... as part of a new generation of binoculars.
The step up from standard to HD optics was more driven by a specific OEM demand than an internal strategy.
Generally, when we upgrade the product it is preferred to be as part of a larger whole scale improvement, not incremental.
Obviously the switch to HD lenses was outside of this strategy.
Click to expand...

Changes are quite significant. Both, silver layers and anti-reflex coatings can be applied using the traditional and cheap vacuum vapor-deposition method - material is vaporized and condenses onto the substrate. A high end multi-coating is made of 5-8 layers and these techniques work well enough to create such a coating.

Dielectric coatings are different: Good mirrors require a very accurate deposition of 30 or so layers, and it requires ion beam sputtering techniques, machines with an initial investment of half a million Euro and all that. Naturally, this is difficult to swallow for a smaller manufacturer. Alternatives: Purchase the prisms, including dielectric coating, directly from the glass makers. But here, one has do deal with mass production, only average quality is available. This is why it is hard to compete with a big manufacturer like Zeiss or Nikon who have dozens of these coating machines standing around.

So I suggest the low-tech alternative: Go Porro, make them really well, and you really don't need any particular high tech equipment for that.

Cheers,
Holger
 
According to their website Meopta does make lenses, prisms, and has AR, metal and dielectric coating capabilities.

I don't know much about vacuum deposition methods but I've believe the latest technologies involve higher temperatures and laser mediated depositions which enables the use of more exotic materials and allows finer tuning of the coatings. I wouldn't know who has that technology or what difference it makes. Anyone know more about it?

David
 
Last edited:
typo said:
According to their website Meopta does make lenses, prisms, and has AR, metal and dielectric coating capabilities.

I don't know much about vacuum deposition methods but I've believe the latest technologies involve higher temperatures and laser mediated depositions which enables the use of more exotic materials and allows finer tuning of the coatings. I wouldn't know who has that technology or what difference it makes. Anyone know more about it?

David
Click to expand...

An anti-reflex coating is also a dielectric coating, so is the P-coating. Sure everybody can make a low-tech dielectric mirror for little money. But to compete with a Zeiss Conquest HD, such a mirror should better be of considerable quality. Perhaps Meopta has got even that technology, and stays with silver coatings for other reasons, but it is hard to imagine which reasons that would be ...

Cheers,
Holger
 
Think how easy applying a nice thick coat of silver must be compared to the complex dielectric stack. There would be a considerable investment in getting the dielectric process going, and considerable effort in application. That is bound to be off putting to a small in-house(innocent until proven guilty!) maker.

What if Meopta started using dielectric, but changed nothing else about the binocular? I can imagine them having to raise the price $200, and most users would wonder, what is the improvement? An accompanying overall design change would make the cost increase more bearable to the buyers. "The All New Meopta", you know.

Ron
 
Ron,
Meopta is not a small company. It has made the Leica Apo-Televids for Leica and the previous Zeiss Diascope telescopes for Zeiss. I have spoken dealers who have visited Meopta and they were quite impressed by the modern well equipped construction facility. Moreover the application of di-electric coatings should not be that difficult for a modern well equipped company.
Gijs
 
Gijs van Ginkel said:
Ron,
Meopta is not a small company. It has made the Leica Apo-Televids for Leica and the previous Zeiss Diascope telescopes for Zeiss. I have spoken dealers who have visited Meopta and they were quite impressed by the modern well equipped construction facility. Moreover the application of di-electric coatings should not be that difficult for a modern well equipped company.
Gijs
Click to expand...

It seems to be a simple business decision on their part. Should they do it or shouldn't they?

Let us assume they don't have these machines or they would be using them very shortly for making dielectric prisms.

How much would it cost Meopta to put in the correct coating machines and then how many binoculars would they have to sell to get back their investment in the machines? Perhaps they could be used for other optical instruments. Once more it would be time to call in the numbers crunchers again to see if they would still be competitive in those enterprises.

Bob
 
ceasar said:
It seems to be a simple business decision on their part. Should they do it or shouldn't they?

Let us assume they don't have these machines or they would be using them very shortly for making dielectric prisms.

How much would it cost Meopta to put in the correct coating machines and then how many binoculars would they have to sell to get back their investment in the machines? Perhaps they could be used for other optical instruments. Once more it would be time to call in the numbers crunchers again to see if they would still be competitive in those enterprises.

Bob
Click to expand...

I think the problem are not alone the machines. To operate and adjuste these machines is a quite delicate process that requires special know-how of well-educated experts. Now that Leica and Zeiss have left them I could imagine that some input is missing at Meopta.

Steve
 
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