Part of my pinhole lens project, which will have its own post very soon, here is a quick measurement of the diameter of Thorlabs P300D Precision Pinhole.
I made the measurement using a Zeiss Stemi 508 Stereo Microscope (max. magnification 5X) with a stage micrometer (0.1mm per division), and photos are taken with a Fuji X-T2.
Here is the stage micrometer, each division is 0.1mm.
Here is the pinhole over the stage micrometer, which shows 3 divisions, so 0.3mm as specified.
Here is the actual pinhole (mounted inside a 1 inch metal disk).
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