Many binoculars on the market today come with upgrades that cost more but significantly enhance the quality of the image you will see.
To help you sift through the information to work out which upgrades are most worth your money, we take a closer look at ED and HD glass. What are they and how can they improve your bird-watching experience?
What is an ED (extra low dispersion) lens in binoculars?
ED glass stands for ‘extra-low dispersion’ glass.
It refers to a special kind of glass used for optics like binoculars for birding. It was developed to contain properties that enhance the viewing experience for the user of the optical instrument.
ED glass is used to make the lenses for high quality binoculars for birding. The optical properties of this kind of glass make it superior to conventional glass.
Its specific role is to reduce or correct an issue that can hamper the performance of binoculars and other optics. This issue is called chromatic aberration.
What is chromatic aberration in binoculars?
Chromatic aberration is the term used to name the effect of color fringing that you can get when looking through a lens or pair of lenses at an object. It can appear as if there is a sort of rainbowed halo around a subject.
Chromatic aberration can be more noticeable around the outer edge of a paler object, particularly against a dark background. It also affects the focus of an image, making it softer.
This type of distortion is an issue when you are trying to distinguish fine details and you need to be confident that the color you are viewing is totally true to life.
What causes lens chromatic aberration?
This effect happens because of the composition of light. The light that we see is made up of waves of different lengths. We perceive the spectrum of color due to the differing wavelengths of the visible light.
When you are using an optical instrument, the light waves enter the instrument through a lens. As these light waves enter a single lens, they are directed or bent by the lens.
When this happens, the light is split into different colors. It is dispersed.
Because the light waves are of different focal lengths, they do not all reach exactly the same point. This is what causes the effect of chromatic aberration, which can be seen at the edge of the object.
What is ED glass in optics?
Ordinary, conventional glass can solve this problem, up to a point. But it cannot totally eradicate it.
There can still be a secondary spectrum visible. This is called secondary, or residual, chromatic aberration.
To correct the issue, manufacturers have created a uniquely specialized type of optical glass with properties that cause an extra low dispersion of light.
What is ED glass made of?
Some manufacturers may refer to binoculars featuring ED glass as containing calcium fluoride, or fluorite, which is the mineral used in the manufacture of the glass.
Does ED glass make a difference?
ED glass greatly reduces the effect of color fringing. It does this by limiting the dispersion of the light waves when they pass through the glass.
Extra low dispersion glass is better at focusing the light waves into a single point and allowing the eye to view color better around the borders of an image.
Binoculars with extra low dispersion glass also have a more effective light transmission through the body of the instrument. Consequently, there is a marked improvement in the vibrancy and accuracy of color.
Overall, it produces an image of a much higher quality. Sharpness and contrast are also increased.
Benefits like this are also more apparent at times of the day or weather conditions where light is low.
ED vs HD glass in binoculars for birding
Different manufacturers use different terminology to describe their products. You will also see binoculars and other optics that boast high definition or HD glass.
What is HD glass?
Unfortunately there doesn’t seem to be one standard answer to this question. Whereas ED glass refers to a particular type of glass manufactured for optics, with very specific properties, HD glass is a term that is used more loosely and to describe different advantages.
In some instances, ‘HD glass’ is used primarily to promote the perception of the product, without any specific reference to a feature.
Confusingly, some companies use it to mean ‘high definition’, a term that consumers are used to hearing in reference to products such as TVs, promising a better quality of picture. Other companies use the term HD to explain that their lenses are made of ‘high density’ glass.
Is HD glass worth the money?
What bird watchers are looking for is a product where the HD glass denotes that special lens coatings have been applied.
Top brands coat their lenses to reduce reflection and combat glare. It is worth checking for these lens coatings in binocular specifications as you will get a better quality view.
What is the difference between ED and HD glass?
HD glass does not necessarily mean that you will automatically be getting ED glass. The terms can be mistakenly used interchangeably, so confirm this in the spec of the optics.
Obviously if you get a pair of binoculars with both ED and HD, this is a bonus. One of our top picks in Best Binoculars for Birding, for example, is both HD and ED:
Vortex Optics Diamondback HD 10×42 Binoculars
Does ED glass make a difference?
In comparison with a pair of binoculars with conventional glass, objective lenses with extra low dispersion glass receive and direct the light more effectively.
Without the issue of chromatic aberration, or color fringing, it is much easier to differentiate details, particularly at longer distances. As well as an increased brightness, bird watching binoculars featuring ED or HD glass benefit from finer details.
Final thoughts: is ED glass worth the money?
Chromatic aberration is more distinct on cheaper makes of binoculars. Brands that use high quality components overall – and high quality glass in particular – will not suffer to a massive degree from this issue. You can still get decent binoculars that do not have extra-low dispersion glass.
That said, it is definitely something to be aware of. ED glass is worth the extra investment if you can afford it.
ED glass is a significant upgrade as it boosts the sharpness and vibrancy of the colors, lessening any chromatic aberration. In practice, this means birders are able to appreciate the full spectrum of color without rainbow-type halos around the subject.
Sometimes it’s good to know that you have found the very best binoculars you can for your money. Fortunately it is now quite a common feature so you will have a lot of top models with ED glass to select from, even at a lower price point.
- 1 What is an ED (extra low dispersion) lens in binoculars?
- 2 What is ED glass in optics?
- 3 What is HD glass?
- 4 What is the difference between ED and HD glass?
- 5 Final thoughts: is ED glass worth the money?