ED Glass and Binocular?

[stereotruckdriver]

Hi all still new here. I just wanted to throw this out. I always believed and learned that ED glass wasn't necessary in a Binocular and that one didn't need it? ED and the like were for Scopes and then you did not notice until higher powers 40x plus or for Photo purposes? Now people like Pentax, Vortex etc... Zeiss and now Leica HD have added to the hype! Now most high end glass is amazing compared to what we all have used through-out the years. I must confess that I always thought Swaro and Leica amongst others were acctually using some sort of ED glass, I mean the views were awesome? Now prices are getting higher and company's that I thought were using ED glass are now advertising using ED or some other propriertary glass? What were they using before? Does ED glass make a difference? I say yes, indeed it does make a difference. Just look what can be had at $ 500 the Vortex Viper! You take away the ED and what do you have? Legend maybe Monarch? And my favorite Pentax DCF ED, in my opinion yeah it's not as robust as an SLC but gives an equal and in some respects better view! So are the alpha's back pedaling or are the new models going to be better than any thing we have ever viewed through? Or are company's like Pentax and Vortex utilizing what the others have been doing all along and have just come up to speed? I mean you could by Swaro or Leica for $8-900 before? So 800 or $2000.00 Umgh! Any ways sorry to ramble on, or for ruffling any feather's. Good Day to you all. P.S. I really like this forum, it's a wealth of info!!!!

[Pinewood]

I enjoy using my Zeiss FL, not for absence of chromatic aberration, but for the color contrast and color quality. I believe that the reduction of CA in a low power binocular by using FL glass may not be obvious, but the crispness of the details and the improvement in color gradations are noticeable to many but not all users. Whether this is worth the extra money is the buyer's decision.
As to American prices, look at the devaluation of the dollar for a significant part of the price increase.

Happy observing,
Arthur

[henry link]

This is a bewilderingly complex topic. Unfortunately comparing binoculars usually consists of comparing one black box to another. Its very easy to fall into the trap of attributing a difference we see to a design difference we happen to know about.

I'm certain that all of these new "ED" binoculars will not perform equally well. Some examples will probably be no better, possibly worse, than some convention binoculars at suppressing longitudinal CA because not all "ED" glass is equal and the choice of matching glass types is just as important. Even in conventional binoculars there are obvious differences in freedom from longitudinal CA from different objective sizes with different focal ratios. Then there are the natural variations in CA that result from the stopdown imposed by the eye under different lighting conditions.

It is possible to test binoculars for longitudinal CA. I do this by placing an 8x telescope behind the eyepiece to boost the magnification 8 times and look at a high contrast white on black target in sunlight. This not only shows the color fringe magnified 8 times, but also shows the total CA from the entire objective. Before I wrote this I compared a Zeiss 8x42 FL to a Nikon 8x32 SE. At 64x the Zeiss has a fraction, perhaps 1/3, of the longitudinal CA visible in the Nikon at 64x. If I stop down the Zeiss to 32mm to match the objective size of the Nikon almost all of its longitudinal CA disappears. If I stop down both binoculars to 24mm to correspond to the stop down imposed by the eye in sunlight then both look essentially free of longitudinal CA even at 64X. At 8x I can see no hint of longitudinal CA on the target through either binocular in sunlight.

What I do see, however, in both binoculars at 8x is plenty of lateral CA, some quite close to the center or even directly on axis if I decenter my pupil slightly. The Zeiss is a little better near the field center, but actually becomes worse than the nikon from about 10 degrees off axis to the edge. One thing I am certain about is that the familiar complaints birders voice about "CA" is not longitudinal CA at all. If you can actually see a color fringe on a dark bird or branch against a bright sky you are seeing lateral color. Lateral color results from uneven magnification of different wavelengths at different positions in the field. It's easily to tell lateral color because objects will show a fringe of one color on the side facing the center (usually red) and a different color on the side facing the field edge (may be green, blue or yellow). Lateral CA is worst at the edge of the field and comes and goes with shifts in pupil position of the eye. Longitudinal CA is a purple fringe which radiates from objects equally in every direction and is equally bad for objects everywhere in the field. Lately I've been testing different binoculars for lateral color trying to determine all the possible sources in binocular designs. Alas, it has turned out to be another bewilderingly complex subject, full of unexpected variables. Sometime soon I hope to start a thread to share everything I don't know about it.

[FrankD]

Sometime soon I hope to start a thread to share everything I don't know about it.


I eagerly await that day Henry. Your contributions are always appreciated.

[trashbird]

Henry Link saith:

"It is possible to test binoculars for longitudinal CA. I do this by placing an 8x telescope behind the eyepiece to boost the magnification 8 times and look at a high contrast white on black target in sunlight. This not only shows the color fringe magnified 8 times, but also shows the total CA from the entire objective."

So what you are saying is that CA can only be detected if you magnify the binocular image 8x? What I am getting from this is don't use an 8x telescope on your bino when you are looking through them. :)

[henry link]

Trashbird,

What I meant to saith was: "It's easier to see things when they're big."