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How
to Select Magnifiers
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Diamonds are graded
for clarity at 10X. If a flaw in a diamond cannot be seen by a trained
eye at 10X, the flaw does not exist for the purpose of grading clarity.
-
A 10X triplet loupe
is the conventional jewellers' loupe. A triplet has three lenses which
greatly reduce or entirely remove distortion and colour aberrations (depending
on the quality of the loupe), compared to single lense or doublet loupes.
-
Magnifiers are also
classified by working distance (focal length). A 10X loupe has a working
distance of 1" which means the magnifier will be in clear focus when
held 1" from an object.
-
The higher the power,
the shorter the working distance,and the shorter the depth of field
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More
on How to Select Magnifiers
This information
was obtained with permission from Grobet File Company of Canada.
Precision work routinely
requires magnification to increase the visulal size of objects. As the
eye comes closer to an object, the apparent size and detail in increased;
however, the ability of the eye to focus correctly diminishes at distances
closer than 10" (254mm). Use of a magnifier provides increased focusing
power, resulting in the visual effect of a clearer, larger image of the
object.
Four
Characteristics of Magnifiers
-
Power of Magnification
The ability of the lens to increase the visual size of an object. The symbol
X (times) is used to identify this factor. A magnifying lens bends light
rays resulting in an image that looks larger than the actual object. For
example, a 3X magnifier triples the size of an image.
-
Working Distance
( Focal Length ) In addition to
power, a magnifier will also be classified for working distance. The higher
the power of a lens, the shorter the working distance (the distance between
the object and the magnifier). For example, a 2X lens has a working distance
of 5" (127mm), which means that the magnifier will provide double magnification
and be in clear focus when held at a distance of 5" from the object.
-
Field of ViewThe
size of the area that is seen through the magnifier. The field of view
decreases as the power increases.
-
Depth of FieldThe
distance that a magnifier can be moved from an object and still have the
object in focus. The higher the power, the shorter the depth of field.
Corrective
Magnifiers
Certain magnifiers
have lens systems which correct optical distortion or aberration that might
otherwise be present as follows:
Distortion
Uncorrected lens will curve "straight lines" of light toward the centre.
Chromatic and
Spherical Aberration Size
and shape differences will occur in the image of an uncorrected lens. These
aberrations are clearly noticable when viewing a matrix of dots of the
same size.
Definition
of Common Terms
-
Achromatic Lens:
Lens that eliminates chromatic aberration.
-
Aplanatic Lens:Lens
that corrects for spherical aberration and coma.
-
Chromatic Aberration:Inability
of a lens to focus light of different colours at a point.
-
Coma:
Blurry appearance around an object viewed through an uncorrected lens.
-
Corrected Lens:
Lens system that corrects for distortions and aberrations to produce a
sharp image.
-
Spherical Aberration:Lens
defect that produces an image that lacks contrast.
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Hearts
and Arrows Loupe
This loupe will show
whether an Round Brilliant Diamond is perfectly cut. A symmetrical pattern
of eight arrows will be seen when viewing a perfectly proportioned stone
from the top - a symmetrical pattern of eight hearts will be seen when
viewing the bottom. If the stone is not perfectly cut, the patterns will
not be clear and symmetrical.
The Hearts and Arrows
loupe is a valuable promotion tool for diamond sales, and it is
portable.
1015 Hearts
and Arrows Loupe $39.95
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|
Optivisors
Most popular head
magnifier, comfortable headband, adjustable to fit any size. Prismatic
lenses are ground and polished. Lens plates can be ordered separately.
DA2 Optivisor
1-1/2X, Working Distance 20" $39.95
DA3 Optivisor
1-3/4X, Working Distance 14" $39.95
DA4 Optivisor
2X, Working Distance 10" $39.95
DA5 Optivisor
2-1/2X, Working Distance 8" $39.95
DA7 Optivisor
2-3/4X, Working Distance 6" $39.95
DA10 Optivisor
3-1/2X, Working Distance 4" $39.95
Optivisor
Lens Plates Only
LP-2 Optivisor
Lens Plate for DA2, 1-1/2X, Working Distance 20" $29.95
LP-3 Optivisor
Lens Plate for DA3, 1-3/4X, Working Distance 14" $29.95
LP-4 Optivisor
Lens Plate for DA4, 2X, Working Distance 10" $29.95
LP-5 Optivisor
Lens Plate for DA5, 2-1/2X, Working Distance 8" $29.95
LP-7 Optivisor
Lens Plate for DA7, 2-3/4X, Working Distance 6" $31.95
LP-10 Optivisor
Lens Plate for DA10, 3-1/2X, Working Distance 4" $31.95
LP1 Optiloupe
$10.95
Fits on either side
of optivisor and adds 2X to the magnification. Optiloupe attachment
can be adjusted away from lenses when not in use.
Watchmaker
Type Eye Loupes
Inexpensive watchmaker's
type loupe in black plastic holder. Good quality lens.
X10010
Watchmaker Type Eye Loupe, 10X, Working Distance 1" $4.95
X07015
Watchmaker Type Eye Loupe, 7X, Working Distance 1.5"
$4.95
X05020
Watchmaker Type Eye Loupe, 5X , Working Distance 2"
$4.95
X04025
Watchmaker Type Eye Loupe, 4X, Working Distance 2-1/2"
$4.95
X03330
Watchmaker Type Eye Loupe, 3.3X, Working Distance 3"
$4.95
X03035
Watchmaker Type Eye Loupe, 3X , Working Distance 3-1/2"
$4.95
X02540
Watchmaker Type Eye Loupe, 2.5X, Working Distance 4"
$4.95
X02345
Watchmaker Type Eye Loupe, 2.3X, Working Distance 4.5"
$4.95
Bausch
& Lomb Loupes
B&L
Hastings Loupe 10X - Professional Jewellery Loupe
Triplet lens, high
quality prismatic. Eliminates colour degradation and gives an undistorted
wide view.
82900 B&L
Hastings Triplet Loupe 10X $79.95
B&L
Coddington Loupes
Single Lens with
a grooved diaphram around its circumference. High definition, distortion-free
view. A black iris masks all distortion that would otherwise be discernable
around the outside of the field of view.
83500 B&L
Coddington Loupe 10X $49.95
83700 B&L
Coddington Loupe 20X $49.95
Jeweller's
Loupes & Magnifiers
These loupes are
excellent for the price. There is some distortion at the extreme edge of
the field of view, unlike the B&L loupes that have no distortion. Made
in China. Not all colours are always available.
15 mm 10X Chrome
Doublet $9.95
20.5 mm 10X Triplet
- Black, Blue, Green, Gold, Silver, Rose, Chrome $31.95
20.5 mm 10X Triplet
with Rubber Grip - same colours $39.95
18 mm 10X Triplet
- same colours $29.95
18 mm 10X Triplet
with Rubber Grip - same colours $36.95
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Lacy West Supplies Ltd.
www.lacywest.com