knot of striped hair

[rjlittlefield]

Recently the forum has had some illustrations and discussion of hairs with cloudy centers (HERE and HERE).

It happens that I have quite a lot of that stuff. This sample seems typical of what I've seen through microscopes since I was a kid -- a broad flattened strand, dark on the sides and light in the middle.



If you can see crossed-eye stereo, this closer view may make clear that the light-colored stripe runs through the center of the hair.



A better illustration is provided by this cross-section, cut with scissors a few mm away from the knot (again, crossed-eye stereo).



Mitutoyo 20X NA 0.42 objective on Raynox DCR-150 tube lens at infinity focus, so about 20.8X optical magnification onto APS-C sensor, cropped for display here. Maximum width of the hair shaft measures 112 microns. Shot as 193 frames with focus step 0.002 mm ( =2/3 of nominal DOF).

--Rik

[rjlittlefield]

Here is a version that has been tweaked for better esthetics: flipped vertical so the "tails of the bow" point downward, and with background masked to black in those troublesome overlap areas where background is always covered by some OOF blur from the subject so it develops a hazy glow.



--Rik

[grgh]

Rik,
Perhaps it's my ageing eyes, I very much prefer the Flipped view. As you say better aesthetics,but for me its seems more depth of field together with a better "true reflection" of 3D appearance.

[MarkSturtevant]

Very good. I was wondering if flattened hair strands are also curly.

[rjlittlefield]

Perhaps it's my ageing eyes, I very much prefer the Flipped view. As you say better aesthetics, but for me its seems more depth of field together with a better "true reflection" of 3D appearance.

That's very interesting! My best guess is that the difference is something to do with the apparent direction of illumination. In the original orientation, as shot, the illumination was actually coming more from the top than the bottom. But somehow the hair on the left side of the image was twisted so that its physical bottom ended up reflecting the light more. That may be confusing the perception of depth. Doing a vertical flip of the image makes the light appear to come more from the top, despite that now it actually is coming more from the bottom!

Very good. I was wondering if flattened hair strands are also curly.

Thanks! Yes, flat and curly is how the trend goes. This particular hair was what I'd call wavy, growing on lower abdomen just below the belt. The hair on my head is much straighter, with a more circular cross section, also thinner and mostly gray or transparent these days. Hair on my forearms is intermediate.

The FBI document that BugEZ found, linked HERE, has a fascinating discussion of hair forms. (The document is entirely textual, no images.)

--Rik

[StanMoller]

Honestly, this is the first time I've seen and heard this kind of information about hair. For me, human hair resembles animal hair under a microscope. It is a tube filled inside with carotene (pigment) and covered on the outside with small scales. If these scales fit tightly together, the hair looks smooth and shiny. But dull and unruly hair has a different picture under the microscope - the scales are "shaggy" and tangled. But at least this information is still very useful to me. After all, I decided to study at www.nwcollege.edu, first as a nail technologist and then to master the profession of a hairdresser.