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Zeiss ED, AOL and FL Glass

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/16/2005 at 15:07
Chris Farris View Drop Down
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Here is a copy of an e-mail from Zeiss discussing the differences in their glass.

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The normal glass used in optics uses lead, arsenic and other "heavy metals" to increase density so that it bends light more sharply. This also adds to the weight of the glass, introduces some color to image, and absorbs some light. By eliminating the heavy metals, we make the glass both lighter in weight, and more transparent, but we have to then use more elements (glass to air surfaces) to get the same amount of bend. This is a good trade off, since the net effect is a brighter, lighter, more color neutral optic. This is the AOS.

FL glass is used for a completely different reason. Remember the part in the training about "Chromatic Aberration" or "color fringing." Color fringing (which is easy to see in competing products, and even in our Victory II and Conquest binoculars) is caused by the fact that glass bends each color of light at a slightly different angle, so you can't bring all the colors to the same focus. If you focus for red/yellow light (which our eyes are most sensitive to) there will be tiny (to quite large, depending on the quality of the optics) fringes of blue/green on one side of high contrast objects, and yellow/red on the other. The cure is ED glass: extra low dispersion glass which bends all of the colors of light at relatively the same angle. However, to make ED glass you have to add even more heavy metal, making the glass much heavier and even less transparent.

FL glass is glass with Fluorine ions suspended in it. Fluorine, in its pure form, is a gas, and even in compounds (Fluorides, among which is "Fluorite" which is used as a lens material by both Kowa and Leica in their spotting scopes) it is relatively light in weight. Fluorine also has a very low "index of dispersion" which means that it bends all the colors of light at just about the same angle. Unfortunately, fluorite is hard to work, fragile, extremely toxic, and chemically active which means that Fluorite elements don't have the best reputation for stability. Suspending the fluorine ions in optical glass produces a glass with the dispersion of ED or a Fluorite element, but without the weight and limited transmission of ED, or the stability problems of Fluorite. Best of  both worlds.

You can see that the Diascopes have practically no color fringing in an extremely bright, color neutral image, and the new NV 42FL binoculars will have that same color purity and extreme brightness. Anyone can see the difference, once it is pointed out to them. We will make up some POS materials to show the difference even under artificial light.

 

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/29/2005 at 09:58
Rusty View Drop Down
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AOS Question?

 

Chris,

 

Does the AOS system have any aspherical elements/lenses?  I have notice the VII I have has little or very minor distorions near the edge of the field.  And yes, the VII does have a fair amount of CA, even in the center on challenging objects (this is really the only negative I have for these binos).  I will write up a review/comparison I did between the VII and Pentax DCF WP later on in the review section.

 

Rusty

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/06/2005 at 13:32
Chris Farris View Drop Down
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No aspherics but a very sophisticated 4 element, thin element, air-spaced objective. "The Vlls show a below average amount of secondary color fringing in the center of the field on the most challenging targets"...certainly less than Swarovksi and the Leica Ultra Trinovids. The FLs eliminate that color and are far superior to the ELs and the new Leica Ultravids.

 

Birding and Observation Product Specialist
Carl Zeiss Optical, Inc.
Carl Zeiss Sports Optics Division
13005  N. Kingston Avenue
Chester, VA 23836 USA

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/06/2005 at 17:54
Rusty View Drop Down
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I love my 10X40 VII's, but they do have some CA.  However, in mid to low light, they are still better than most current  binos.

 

Rusty

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/11/2005 at 08:07
Rusty View Drop Down
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Chris,

 

I really checked the Victory II carefully in the center of the field, and you are correct.  The center 25 - 30% of the field has very little CA, probably less than SLC's, Leicas, and EL's..  However once you look out of the center 30%, there is CA.

 

Rusty

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