diracpoint
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My cheap macro lens arrived a few days ago, so I decided to take a closer look at the hand engravings. Lines that appear like surface scratches to the bare eye, reveal a very nice three-dimensionality: One more: Now, from the macro images we can do a little “back of the envelope” calculation to estimate the width of each groove. In the picture below, the real dimension of the bottom side of the bridge is roughly 5 mm (orange arrows). At the center we have 6 side by side grooves (pink arrows), and the length of that segment is roughly 1/3 rd of that side=> 5/3=1.67 mm (green arrow) Since this segment has 6 grooves (pink arrows), the width of each groove (their widest part) is 1.67 mm/ 6=278 microns. To put it into perspective, from Wikipedia, “human hair varies in diameter, ranging anywhere from 17 μm to 181 μm”. 😉😆 So, the widest part of the groove is about two human hairs thick (or less, depending on the type of hair you take 😀), and then it becomes narrower than that towards the center. It’s also interesting to note how sharp their narrowest points are towards the center! How they do all of these just by hand is mind blowing! 🤯 
And without the b/w filter: 
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