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Analog photographers use loupes to review, edit or analyze negatives and slides on a light table. Typical magnifications for viewing slides full-frame depend on image format; 35 mm frames (24×36 mm slides to 38×38 mm superslides) are best viewed at ca. 5×, while ca. 3× is optimal for viewing medium format slides (6×4.5 cm / 6×6 cm / 6×7 cm).
Magnifying glasses typically have low magnifying power: 2×–6×, with the lower-power types being much more common. At higher magnifications, the image quality of a simple magnifying glass becomes poor due to optical aberrations, particularly spherical aberration. When more magnification or a better image is required, other types of hand ...
The invention of reading stones is often credited to Abbas ibn Firnas in the 9th century, [1] although the regular use of reading stones did not begin until around 1000 AD. [ 2 ] [ 3 ] Early reading stones were made from rock crystal (quartz), beryl and glass, which could be shaped and polished into lenses used for magnification.
By convention, for magnifying glasses and optical microscopes, where the size of the object is a linear dimension and the apparent size is an angle, the magnification is the ratio between the apparent (angular) size as seen in the eyepiece and the angular size of the object when placed at the conventional closest distance of distinct vision: 25 ...
Because the tops have magnets only at the corners, there's a slight gap in the center between the top and the frame — but it's not noticeable to you as the wearer and barely noticeable to onlookers.
Given as the first number in a binocular description (e.g., 7×35, 10×50), magnification is the ratio of the focal length of the objective divided by the focal length of the eyepiece. This gives the magnifying power of binoculars (sometimes expressed as "diameters").
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