A customer who bought a set of Hawke Frontier ED 8×43 binoculars from the Northern Optics weekend display at the Waters` edge visitor centre, Lincolnshire asked what ED stood for in the description.
I explained that with normal binoculars not all colours come to the same point of focus. This means you get some chromatic aberration (false colour) and slightly reduced sharpness and brightness in comparison.
So as a practical demonstration I asked the customer to look at a heavily back lit lamp post with non ED binoculars. So as to level the playing field I used Hawke ED 10×32 and non 10×32. He noticed that the non ED model gave some red and purple colour fringing down the edges of the post (chromatic aberration). The when the ED 10×32 where used, there was a marked drop in false colour and in his words a much better overall viewing experience.
Then we went up a notch to the Hawke Frontier ED 8×43, where there was a noticeable further reduction in CA due to the higher grade glass. Although ED glass does not completely illuminate CA , it vastly reduces it.
As with our customer, it is always best to buy binoculars from a place where you can see through them, plus have a vendor with a in depth knowledge of optics.