Leica 10x42 BRF manual Glossary, Color errors chromatic aberrations Every image-forming

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Glossary

Astigmatism Because of the naturally curved shape of a lens, not all light rays converge on the same plane. While the center of the picture is sharp, the edge of the picture appears to be out of focus. One can cause objects in one or the other plane to be rendered sharply by refocusing. In addition, astigmatism causes the sharpness of an object detail to be influenced by its orientation. This effect becomes stronger towards the edges of the image. For example, if we look at the corner of a picture of a chain link fence, it will be noticeable (if astigmatism is present) that the wires that point towards the center of the image are reproduced with a diffe- rent degree of sharpness than those that are oriented at a right angle to them.

By refocusing, one or the other wire direction can be rendered sharply, but not both of them at the same time. This effect can be reduced by appropriate optical design measures, but it cannot be eliminated completely. Astigmatism leads to a significant impairment of the image quality.

Distortion The term distortion is used to describe the effect that causes the image of an object to be rendered with a non-uniform reproduction ratio. For binocular observation, unlike in photography, this effect is applied quite deliberately to reduce the so-called “globe effect” caused by perspective observation and by swinging the binocular. To the observer, the image created in this manner appears straightened out. There are two kinds of distortion : pincushion distortion (illustrated on the top), and barrel distortion (as shown on the bottom). Observa- tion through a binocular that does not have deliber- ately implemented judicious distortion is quite un- pleasant.

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Color errors (chromatic aberrations) Every image-forming

 

component made of glass – such a lens elements – refracts

 

light rays of different colors at different angles. This results in

 

the fact that not all the light rays that emanate from a multi-

 

colored point on the object are re-united at a single point in

 

the image. This results in color errors for the observer. Color

 

errors become particularly evident to the observer as color

 

fringes when high magnifications and long focal lengths are

 

being used, as they are in spotting scopes. Pictorial examples :

 

Color errors appear primarily as color fringes around dark

 

objects in front of bright backgrounds, as illustrated by the

 

example on the left with the red-fringed feather dress. With

 

APO correction of Leica (right illustration) such color effects

 

are no longer discernible.

 

 

 

Optical glasses with anomalous partial dispersion

APO color error correction APO stands for apochromatic

Light rays of different colors are refracted at different angles

color error correction. It is only beneficial for lenses with long

through the lens elements. This effect is called dispersion and

focal lengths and for high magnifications, like in spotting

in different types of glass it is present at different levels of

scopes. Apochromatic color correction is achieved by the use

strength. Most types of glass have typical, “normal” charac-

of special types of optical glass with anomalous partial disper-

teristics. Special glasses with “anomalous partial dispersion”,

sion and with glasses that contain fluorite. Such correction

on the other hand, have characteristics that are different in

results in images with enhanced sharpness, increased contrast

certain ranges of colors, and this makes a special color error

and an extremely natural color rendition.

correction possible that cannot be achieved with normal types

 

of optical glass. Glasses with anomalous partial dispersion

 

are used for the enhancement of image quality, and they are

 

used in all Leica binoculars and spotting scopes.

 

High refraction glasses Lens elements made of high refraction glasses bend light rays more strongly than lenses with the same shape that are made of standard glasses. Therefore the use of a lens element made of high refraction glass can achieve strong effect without the need for lenses with excessively strong surface curvatures. This helps to prevent imaging errors, thus leading to greater imaging performance. High refraction optical glasses are used in all Leica binoculars and spotting scopes in order to make their short construction possible.

ASPH. ASPH. is an abbreviation that denotes the use of at least one aspherical lens surface in an optical system. Unlike regular spherical lens surfaces, aspherical lenses have a curvature near their edges that is different from the curvature in the center of the lens. That makes it possible to influence light rays passing through the edges of the lens differently from light rays passing through the center portion of the lens. It also makes it possible to achieve several correction goals simultaneously with only one lens element. Furthermore it helps to reduce the weight and the physical size of an optical system and it makes certain imaging characteristics possible to begin with. Such surfaces help to increase the image quality or to influence the distortion. The fabri- cation and the handling of aspherical lens elements is significantly more costly, however, than that of conventional spherical lenses. In order to assure the extremely high image quality in all models of Ultravid binoculars, aspherical lenses are used effect- ively in the 25 mm and 20 mm BR / BL models. In the remaining models the high image quality is achieved by means of complex optical systems that consist of several lens elements.

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Contents Leica Sport Optics Leica Digiscoping Page Yellow Wagtail / Motacilla flava Spanish Imperial Eagle / Tringa totanus Leica Camera Inc has been One of these entities American Birding Association ABA, USA Duovid class Two binoculars in one Leica Duovid 10 +15 x Leica Duovid 8 +12 x Leica Duovid 8 +12 x 42 the most flexible 42 mm binoculars Leica Duovid 10 +15 xLeica Duovid 8 +12 x Duovid class Two binoculars in one Leica Duovid 10 +15 x 50 the binocular-spotting scopesBlack Order No Green Order No Ultravid class Binoculars for extreme demands Leica Ultravid 8 x 20 BL Leica Ultravid 12 x 50 BR Leica Ultravid 8 x 50 BR Leica Ultravid 10 x 50 BRLeica Ultravid 12 x 50 BR Leica Ultravid 7 x 42 BRLeica Ultravid 8 x 42 BL Leica Ultravid 10 x 42 BLLeica Ultravid 8 x 32 BR Leica Ultravid 10 x 32 BRLeica Ultravid BR 25 mm the stars among the compacts Leica Ultravid 10 x 25 BRLeica Ultravid 10 x 25 BL Leica Ultravid 8 x 20 BR Leica Ultravid 8 x 20 BLLeica Ultravid BL 42 mm lightweight in a classic design Ultravid class Binoculars for extreme demandsLeica Ultravid BR 50 mm ready for any light conditions Leica Ultravid BR 42 mm the robust all-rounderLeica Ultravid BR 32 mm always with you 20 BL Order NoTrinovid class Proven technology for Leica Trinovid 10 x 42 BN Leica Trinovid 8 x 20 BCA Leica Trinovid 8 x 42 BN Leica Trinovid 10 x 42 BNLeica Trinovid 8 x 32 BN Leica Trinovid 10 x 32 BNLeica Trinovid BCA 25 mm and 20 mm distinguished compact Trinovid class Proven technology for the ambitious viewerLeica Trinovid BN 32 mm the constant companions 20 BCA Order NoTelevid class High-performance spotting scopes Leica Televid Leica APO-TELEVID Leica Televid 77 ensures the viewer Great detail recognition, even under the worstLight conditions Scott Roederer, birder and author, USA WW/16 WW/26 x WW WW/32 x WW 20-60 x/16-48 Order No Leica APO-TELEVID 62 true color rendition in a compact formOrder No Leica Digital Adapter Vertical or horizontal formatRangefinder class Pure precision monocular Leica Rangemaster 900 scan Leica Geovid 8 x 42 BRF Leica Geovid 8 x 56 BRF Leica Geovid 8 x 42 BRFLeica Geovid 10 x 42 BRF Leica Rangemaster 1200 and 900 scan the small big helpers Leica Rangemaster 900 scanLeica Rangemaster 1200 scan Leica Geovid BRF next generation binocular with rangefinder Leica Geovid 56 BRF Observing and rangefindingGreat White Pelican / Pelecanus onocrotalus Technical Data 12 x 50 BR Magnification Front lens diameterExit pupil Twilight factor Eyepieces for eyeglass10 x 32 BR 10 x 25 BR/BL 20 BR/BL10 x 42 BN Armored, black Delivery scope10 x 32 BN 10 x 25 BCA 20 BCA Spotting scopeAngled viewing Delivery Scope Field of viewFilter thread Dimensions W x H x D Straight viewingFocal length of the lens Eyepiece forObjective angle of view Close focusing distance Measuring modePower supply Battery lifetimeTechnical Data Very useful binocular equipment Floating carrying strap, orangeOrder No Neoprene carrying strap, contoured Tripod adapter for binoculars Order No Carrying case for TelevidOrder No Ever-ready-case for Televid Order No Ever-ready-case for Televid 77 Angled viewTechnical binocular terms Example Leica Trinovid 10 x 42 BNOptical quality Color errors chromatic aberrations Every image-forming GlossaryLens without coating Lens with Leica HDC multi layer coatingLeica rangefinder technology with a press of the button
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