In another thread I was seeking information on a 10x40 IF roof prism binocular made by Celestron. Henry Link referred to a book authored by Alan Hale titled "How to Choose Binoculars," which listed that particular binocular model in 1991. (copywrite date of Hale's book) Hale also states "... However during the past few years, some manufactuers have begun coating the roof with an anti-phase shifting material...) page 37.
While Hale was CEO and President of Celestron International, his book is not a promotional piece for Celestron. On the contrary he deals with basic facts about binoculars. It is a useful book for persons starting from scratch in better understanding the basic ins and outs of binoculars.
I had begun to compare the 10x40 IF roof Celestron to other 10 power models in my collection, both porro and roofs. These included: Bushnell Custom 10x50 porro, Leupold Cascade 10x42 porro, Nikon 10x32 LX roof, Nikon E2 10x35 porro, Nikon 10x70 Astrolux porro, Nikon SE 10x42 porro, Nikon 10x25 LX , and Nikon Diplomat 10x25 porro.
Using a tripod platform for steadiness in good light, I assumed the Celestron would not resolve as well as the aforementioned models because it (1) was a roof, and (2) was not phase coated. But I was surprised. Its resolution, colors, and brightness were excellent. It had none of the soft contrast of the old Leitz Trinovids. Focusing on a variety of subjects including an optical chart, animals, distant buildings, and at infinity, the Celestron surpassed every so slightly most of the other binoculars.
Being objective as I can be, the Celestron had the shortest ER, the least depth of field, and although advertised as wide angle, the least useful edges.
But for 50% of the field, it is excellent. Maybe this particular model is phase coated. I have no way of knowing. Being that it is IF, that may be a critical difference in fine tuning the focus to its advantage.
But what amazed me the most is the binocular with the best resolution in the center and the most vivid colors is the discontinued Nikon 10x25 Diplomat. No fooling.
That got me to reading some more, using Wikepedia and the latest Zeiss literature, also from the Zeiss website. It appears that two variations of roofs prisms now dominate the market: Schmidt-Pechan, and Abbe-Koenig.
Both benefit from Phase coatings, but only the Schmidt-Pechan roof requires a reflective coating to be usable.
Aluminum, silver, and dielectric coatings are used, with dielectric being the best for reflecting light. The current Zeiss Fl 32 mm models are Schmidt-Pechan roofs as are some of the Conquest models. The others are Abbe-Koenig roofs and do not require reflective coatings although the phase coatings are necessary and are also considered a dielectric coating, but not reflective. That is my understanding. Confused?
I also learned that water proof roof prism binoculars filled with either nitrogen or argon gas prevents the oxidation which impairs both aluminum and silver reflective coatings since oxygen and hydrogen cannot get into the body. Of course filling any binocular that is not sealed adequately with nitrogen or argon gas will not create a fog proof binocular over time. Straighten me out if what I have written is contrary to accepted facts. Sometimes my grasp of technicalities is inadequate. John
John,
I have used two non-p coated prism roofs that appear to be as sharp and almost as bright as p-coated Nikon Monarchs.
The first pair is a Japanese 9x63 roof, made in the mid 80s (I bought them in 1986 to look at "Halley's Coma" :-).
It looks a lot like the Optolyth 9x63 with the long tubes and dimpled black rubber armoring. They appear to have green MCs only on the outer lens surfaces.
The 9x63s have A-K prisms, so no mystery why the images are not dim and soft in daylight (in low light, the large exit pupil comes into play).
The second is a 20-year-old pair of Swarovski 7x30 SLs. As far as I know, the SLs have SP prisms like the newer SLCs. So this was very surprising.
Other non-p coated prism roofs I've tried such as the Nikon 8x36 Sporter I, Canon 8x32, and Brunton 8x32 Lite-Tech had noticeably softer images and also appeared to be a bit dimmer.
Why the Swaros look sharper and a bit brighter than those other non-p coated roofs is a mystery????
As Henry pointed out on another thread, the EP design on the newer Swaro 8x30 SLC is fairly simple compared to other top roofs. So it's not due to a more complex EP design.
Brock,
When you mentioned comparing the Japanese 9 x 63 with Nikon Monarch's were you thinking of the 8.5 x 56 or 10 x 56 Monarchs?
http://www.eagleoptics.com/binocula...6-atb-binocular
Bob