A quality linen tester with a biconvex white-glass lens and a black aluminum frame (anodized). In the foot (31x31 mm window) is a glass plate with a mm/inch scale with a length/dimension of 20 mm (1 inch). It is foldable and is delivered with a casing for safe storage or transport.

6x magnification with a lens diameter Ø of 28 mm.

• magnification: 6x
• biconvexe glass lens (silicate glass)
• lens diameter: Ø 28 mm
• open window/foot: 31x31 mm
• mm / inch scale (20mm / 1 inch)
• frame material: aluminum
• dimensions:

  height 5.5 cm

  width 3.8 cm

  length 5.3 cm

• weight brass 86 grams
• leather pouch included
• made in Germany

Biconvex lenses are also called convexo-convex lenses and are mainly made out of a special quality glass. Different types of biconvex-lenses exist such as the planconvex-lens. The most common biconvex lens is the symmetric-convex lens as used in this magnifier.

The biconvex lens is manufactured with identical convex surfaces each side of the lens. The focal length is equal to the radius of the curvature. Resulting from its perfect symmetry it produce images close to 1 and up to a magnification of 8x. Biconvex lenses have positive focal lengths and form both real and virtual images.

Aberrations such as coma, distortion, and chromatic aberration almost exactly cancel out also due to the symmetry