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| Warranty: All merchandise
guaranteed from manufacturer's defect.
Returns: Returns only accepted with Return
Merchandise Authorization (RMA). A 15% restocking fee applies
to all returns of saleable merchandise.
Freight: F.O.B. Richmond,
Virginia. Orders shipped USPS or UPS/DHL GROUND. For
Next Day and 2nd Day Air, please call
(800) 537-4410.
Payment Terms: Visa,
MasterCard, Amex, Discover, Diners Club.
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Technical Data
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Useful Information about Magnifiers
and Lenses |
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| Biconvex |
Plano-convex |
Aspherical |
Biconcave |
Plano-concave |
Aplanatic |
Achromatic |
Triplet |
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Table
of Near Vision Equivalents
1 Foot = 12 inches = 0.3048m, 1 inc=2.54cm
m = 3.2808 feet, 1 cm = 0.3937 inch.
* For US-market us dec.: US Snellen conversion |
Magnification requirement
= Visual acuity requirement/
Visual acuity achieved cc |
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Dec.
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Log
Mar
for testing at
40 cm (16
inch)
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*US
Snellen |
Metric
Print Size
for testing at
25 cm
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Npoint
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Metric
Print Size |
1.0 |
0.0 |
20/20 |
0.4M |
N2 |
0.25M |
0.8 |
0.1 |
20/25 |
0.5M |
N2.5 |
0.32M |
0.666 |
0.2 |
20/30 |
0.6M 6Pt |
N3.2 |
0.4M |
0.5 |
0.3 |
20/40 |
0.8M |
N4 |
0.5M |
0.4 |
0.4 |
20/50 |
1.0M |
N5 |
0.63M |
0.333 |
0.5 |
20/60 |
1.25M 12Pt |
N6.3 |
0.8M |
0.25 |
0.6 |
20/80 |
1.6M |
N8 |
1.0M |
0.2 |
0.7 |
20/100 |
2.0M 18Pt |
N10 |
1.25M |
0.16 |
0.8 |
20/125 |
2.5M |
N12.5 |
1.6M |
0.125 |
0.9 |
20/160 |
3.2M |
N16 |
2.0M |
0.1 |
1.0 |
20/200 |
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N20 |
2.5M |
0.08 |
1.1 |
20/250 |
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N25 |
3.2M |
0.065 |
1.2 |
20/320 |
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N32 |
4.0M |
0.05 |
1.3 |
20/400 |
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N40 |
5.0M |
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| The Equivalent Power of a stand magnifier
(the equivalent spectacle lens power) is the Transverse Magnification
(TM), also called the Enlargement Ratio, multiplied by I meter/Eye-to-image
distance (aE) in meters. Therefore, EP=(TM)*(l /aE). The Transverse
Magnification (-FM) of a stand magnifier is the Lens-to-image
distance (s') / Lens-to-Object distance (s). Therefore, TM=s'/s.
Click
here for details on Stand Magnifiers. |
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