Loupe

Specification

Technical parameters

Overview

A watchmaker's loupe is a single-lens magnifier held in the eye socket, leaving both hands free. Magnification is stamped on the barrel: 2.5× for assembly and general work, 4× for most service work, and 6× to 10× for inspecting pivots, jewel faces and hairspring coils.

The number is a trade. Higher magnification means a shorter working distance and a shallower depth of field, so a 10× loupe is useless for anything involving movement — your hands move further than the field allows. Most work is done at 2.5× to 4×, with a higher power picked up only for inspection.

Optical quality is the difference between a useful loupe and a headache. A cheap loupe with uncorrected distortion will make you misjudge distances constantly, and the resulting eyestrain ends sessions early. An achromatic triplet is worth the cost if you spend more than an hour at a time under magnification.

What matters about it

• Hands-free magnification held in the eye socket
• Power chosen per task, not per preference
• Achromatic triplets reduce distortion and eyestrain
• Working distance drops as power rises
• The cheapest tool you should not buy cheaply

Practical notes

• Start at 2.5× or 4×; go higher only when you need to inspect a surface.
• Hold the loupe with the socket, not your hand, so both hands stay free.
• Pair it with a daylight-balanced bench lamp — magnification without light achieves nothing.
• Clean the lens with a cloth; a scratched loupe is worse than a weak one.

Compatible with