Looks like the Leica people still have to do some explaining. They may certainly need to coordinate better between what the scientists say and what is finally printed after the text has been fitted into the format of the brochure. Also, I assume all those definitions in their brochure date from before announcing the new Ultravids and Televids. So, that text may not be meant for our upcoming new toys.
A few more excerpts...
"Fluoride lenses With the help of new fluoride (FL) glass, in Leica HD and APO
models the color fidelity and contrast of images is further improved. Optical
FL lenses are to a large part made up of calcium fluoride, a mineral with a
crystalline structure. Unlike conventional optical lenses, this creates a very
low level of dispersion (light scattering) and corrects aberration (imaging errors) significantly better. So as a result, the viewing experience is more natural and impressive than it has ever been before."
"High-Definition optics (HD)/Apochromatic color aberration correction (APO) The optics on the new Ultravid and Televid HD models stand apart from conventional optics by way of their increased image resolution performance. The contrast on these models is greater, color aberrations are reduced, the image looks sharper, details are more clearly recognizable, and the color reproduction of the image is extremely natural. This is made possible by optimizing the existing optical systems with the help of new FL lenses.
Here, FL denotes a special type of lens made from calcium fluorite – a crystalline mineral with an extremely low refractive index and very low dispersion (see “color aberration”). Furthermore, these optical glasses offer an impressively high degree of transmission – from UV right into the IR segment of light. By combining FL types of glass with “normal” optical glasses and glasses with anomalous partial dispersion to form achromatic optical systems, chromatic aberration and other imaging errors can be significantly reduced. This performance is only further improved by apochromatic aberration correction (APO), as used in the APO models. They are also
made up of a combination of FL and “normal” optical glasses as well as glasses with anomalous partial dispersion, but are considerably more elaborate, since in their special optical construction they are optimized for three lengths of light waves (primary and secondary spectrum) instead of two (only primary spectrum) – as in achromats. The more compact this kind of optical system has to become, the more complicated its development is. Especially for long focal lengths and high magnifications, this kind of elaborate
APO construction is worthwhile, because in ensures a totally impressive viewing experience."
"LEICA APO-TELEVID 82
Top-of-the-range spotting scope delivering professional standards for all users. An in - nov ative 4-part fluoride lens objective for maximum color fidelity and richness of contrast. Optically neutral front lens glass to
protect the APO optic, and Leica AquaDuraTM coating. Par ticularly short close focus distance of 3.9 meters. Rubber-protected magnesium housing, waterproofed up to 5 meters. Comes with the new variable wideangle
eyepiece 25 – 50 x WW ASPH."