• Welcome to BirdForum, the internet's largest birding community with thousands of members from all over the world. The forums are dedicated to wild birds, birding, binoculars and equipment and all that goes with it.

    Please register for an account to take part in the discussions in the forum, post your pictures in the gallery and more.
ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

Dielectric coating vs ED glass ? (1 Viewer)

I am looking at binoculars in the £150-£200 range ish and I have found several models I like the look of where at the same price point they feature either : dielectric coatings or ED glass


Vortex Diamondback 8x32 = dielectric coating
Celestron Trailseeker 8 x 32 = dielectric coating
Hawke Endurance 8 x 32 = ED glass

Which would you tend to go for at that price point? A dielectric coated model or one with ED glass ?

(also any particular preference for any of the above models or any others to consider? Looking at 8x32/10x32 size for packing in a day pack for general travel and at home for looking out at the ships and the bay from my balcony [Bournemouth UK]).


Found one that has both just inside the price at £199. The Viking Kestrel ED, both dielectric and ED glass. Doesn't seem to have the bulletproof warranty of Vortex or Hawke though. Also no sign of any reviews of this model and hardly any mention of the brand VikingOptics on the net.
Last edited:
Hi Dragon
The quality of a bino is determined by more than just ED glass or prism coating. Some folks prefer the slightly warmer view of silver. Of the models you list I would audition the Hawke as they have a growing reputation and I have heard a respectful comment about them from a competitor.

Last edited:
As far as the Hawke's go, I have recently purchased a pair for my wife and have had no complaints about them. They are light, bright, sharp and, for the price, appear very good value for the money. I have occasionally used them myself when looking at butterflies/dragonflies, when my Leica's will not focus close enough, and have been very satisfied with the views obtained. They are not as good as the Leica's but at 1/8th of the price are excellent value.


I'm Drinking wine at the time of writeing this article. My apologies. Please correct my drunking information below.

(Short answer)

I would seek a bino with a dielectric coating, with minimal chromatic aberrations, over budget ED glass, but in an ideal world I would have both.

Reason/long answers,

Dielectric coatings are created by the depositing metallic materials for example Tantalum Pentoxide (Ta2O5) and/or Aluminum Oxide (Al2O3) in alternating polarized layers. In order to maximize or minimize interference of light refraction effects needed within the optic, normally creating a brighter image over non dielectric coated optics e.g: silver coated/ED lenses

Whereby ED glass (achromatic doublets) uses an positive low-index (crown) element and a negative high-index (flint) normally with a photosensitive polymer layer reducing chromatic aberrations within the binoculars.

Although the chromatic aberrations will be effected by the gradeing of the ed glass depending on material composition and other factors including(can't remember).

In conclusion, I would seek a dielectric coated with ed glass binocular to reduce Chromatic aberrations and increase brightness ect..

Recommendation, would be the Viking Kestrel ED Binoculars or a non ed pair would be ether R.S.P.B WPG or Viking Vistron.
While it's true the best binoculars on the market mostly have ED glass and dielectric mirror coatings there are some extremely good ones costing several times the budget here that lack one or the other, or both.

It seems not everyone is sensitive to CA or can discriminate the colour differences between the different coatings, so it's not a given that you will see any benefit. It doesn't help that the ED class of glass covers a wide range of optical performance, as does the term dielectric coating. At the entry level it can be questionable if there is any benefit at all.

I have tried the original three models on the list, and reviewed the Hawke for the forum. Unfortunately it was a few years ago and there may well have been changes in coating, lens supplier, or even manufacturer in that time, so I'd be reluctant to offer an opinion. I'd only suggest you rely on your own judgement of performance rather than the labelling on the box.

Good luck,

Last edited:
Hi DodgyDave,

Can you explain the photosensitive polymer layer in ED glass?
If this exists, does it exist in telescope ED doublets?
Wouldn't this reduce transmission, and be variable in effect?

Minus blue filters are available for fast refractors to reduce CA, but I don't use them.

Photosensitive layer?? You might put a matching liquid between elements to stop reflections or maybe a UV cure adhesive if that is what you meant.
Different glasses have different refractive index variations... you play with them to minimise the shift in focus with focal point. ED is just one type of glass that can help.
ED and phase coatings are never mentioned with Porros and the view through a Nikon 8x30 still seems wide and clear and crisp....

wllmspd, post 7,
ED stands for extra low dispersion glass and that optical glass type can be used in any sort of binocular.
Phase coatings is a very different ball game and that type of coating is only necessary for roof prisms, where a phase shift occurs between light beams from different prism surfaces. That is not the case in porro prisms, therefore you will never see phase coatings in binoculars with porro prisms. Although I thought that this was well known among readers of Birdforum, your post 7 seems to indicate that his might not be the case.
Gijs van Ginkel
Make a reflectance test artefact from a bit of SF6 glass (I had the melt date), really dense stuff (Extra Dense ;-)

Dielectric coatings and ED glass have different purposes. ED glass is used with the intention of producing a cleaner image (or reduce chromatic aberration if one wants to get into the bino-geekery). Leaded glass was used before ED for essentially the same purpose. Dielectric reflective coatings reflect more light than silver or aluminium mirrors. The use of dielectric coatings in those roof prism binoculars with prism designs that require mirrors will normally result in a slight increase in perceived brightness - but this difference may be too slight for you to notice, especially on a bright sunny day.

typo's comment that it is perfectly possible to design an excellent binocular using neither dielectric coatings or ED glass is one I'd wholeheartedly agree with. How you actually get on with a binocular (looking through it and its feel in the hand) is critical and I think we would all agree you should get your hands on the binoculars you are interested in - side by side if at all possible - and carefully assess them before buying.

NB. if you are looking at ships and such from your balcony, you may find an old 10x50 porro very satisfying to use, especially if you can brace your arms against your rail or use some kind of tripod or mount. Such binoculars should be quite easily (and often cheaply) found in secondhand web sites or newspapers covering the Solent area.
To answer op's question, in thise case I would always take the ED glass rated first.

I would always appreciate a clean chromatic aberration free image over a little bit more brightness and slightly better contrast dielectric prism coatings offer.

You can get the Bushnell legend M, which is affordable, and offers both ED and dielectric prism coating. It has a good following.
And just when you thought it was safe to go back into the water, Bill Cook swims by. It seems that he’s a fellow who, after talking with thousands of customers, is of the opinion that most rhetoric put forth by the average observer concerns things they only THINK they have observed, not considering the many other factors that, while they are not frequently spoken of, play a tremendous part in the various stages of wonderfulness being described.

Some of the things spoken of here, matter. To most observers—except the “A” types—they don’t.

“Stackin’ BBs all night long ... d’light come an me wan’ go home.”—Harryn Belafonte, 1956

(Okay, okay, I took a few liberties.)

Last edited:
Warning! This thread is more than 6 years ago old.
It's likely that no further discussion is required, in which case we recommend starting a new thread. If however you feel your response is required you can still do so.

Users who are viewing this thread