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Hair of the dog

 
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boomblurt



Joined: 18 Aug 2013
Posts: 131
Location: Australia

PostPosted: Thu Sep 29, 2016 6:07 pm    Post subject: Hair of the dog Reply with quote

Inspired by Beatsy's recent "Knot [in] the hair of my chinny chin chin", I tried to do a hair image. It took quite a few attempts to get anything worth sharing - getting decent light at 50x is, to me at least, a black magic that still bamboozles, despite all the excellent information here.

The model was my dog, a Blue Heeler named Jack, who has both dark and light coloured hair. The white hair had a mostly colourless cuticle (Edit: cortex is actually the clear bit here and cuticle is the scaly outer) so I'm thinking that it's the same effect that gives his polar bear cousins their colour.

Mitutoyo 50x, Raynox 150, Canon 6D, flash.


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Geoff


Last edited by boomblurt on Thu Sep 29, 2016 9:01 pm; edited 1 time in total
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Saul



Joined: 31 Jan 2011
Posts: 740
Location: Naperville, IL USA

PostPosted: Thu Sep 29, 2016 8:41 pm    Post subject: Reply with quote

Very interesting - looks like I can see inner and outer layers ?
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Saul
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 17516
Location: Richland, Washington State, USA

PostPosted: Thu Sep 29, 2016 8:51 pm    Post subject: Reply with quote

I agree it looks like there are some sort of layers. Perhaps not inner/outer, but at least front/back.

Any chance we can see this in stereo?

--Rik
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boomblurt



Joined: 18 Aug 2013
Posts: 131
Location: Australia

PostPosted: Thu Sep 29, 2016 8:54 pm    Post subject: Reply with quote

Google informs me that we are seeing three layers there - the cuticle is the outer, scaly layer, while the innermost part is called the medulla. The clear middle portion is the cortex and it normally contains the pigment.

Rik, I don't think I'd be able to stereo this - the retouching was too fiddly.
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Geoff
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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA

PostPosted: Thu Sep 29, 2016 9:27 pm    Post subject: Reply with quote

You might try it without any retouching and see how it looks. I often present a retouched single image, and then a stereo pair with no retouching. Of course the pair will have artifacts, but if the added insight from the stereo is enough, I just live with them.

--Rik
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boomblurt



Joined: 18 Aug 2013
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Location: Australia

PostPosted: Thu Sep 29, 2016 10:55 pm    Post subject: Reply with quote

The stereo was done at +/- 8 but doesn't really help to show the internal structure, to my eyes at least.

To the naked eye the hair is pure white, but under the microscope the clear cortex becomes more apparent as magnification is increased.


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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA

PostPosted: Thu Sep 29, 2016 11:16 pm    Post subject: Reply with quote

Thank you for the stereo. I have pulled your pair into StereoPhoto Maker and examined it with magnification, in parallel view using my best viewer (https://www.berezin.com/3d/pocket_3dvu.htm).

The stereo does make clear that the white portion is internal, not back surface, which is a nice bit of insight.

Other than that, I have to agree that in this case the stereo does not add much. I think this is a tribute to your illumination, which makes the general 3D structure clear even in a single view. Nicely done!

--Rik
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rjlittlefield
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Joined: 01 Aug 2006
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PostPosted: Thu Sep 29, 2016 11:20 pm    Post subject: Reply with quote

By the way, I'm having some trouble believing that the stereo was done with +-8, unless you've done some significant post-processing.

With +-8, some subject features should move a lot to the right, others to the left (in each view).

But in the pair that you've presented, it seems like all features have moved in the same direction although by different amounts. Does this make sense, and can you explain?

--Rik
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boomblurt



Joined: 18 Aug 2013
Posts: 131
Location: Australia

PostPosted: Thu Sep 29, 2016 11:54 pm    Post subject: Reply with quote

I just redid the stereos to confirm that it is +/- 8 ... initially I had done it using smaller values and was surprised to see not much effect. Retouching was cloning out a couple of dust trails, plus levels and a little sharpening.

I've aligned (by positioning) the two images in Photoshop and there is a rotation there, but it's not massive. (Edit: So the right image's right/rear side moves to the left, while the left/front of the right image moves to the right.) Could slabbing be the cause? The stack was 20 slabs, with about 200 images in total.

Edit: Also I don't think that the hair and knot are the same distance from the lens. I suspect (but can't recall for sure, as I did a few versions) that the knot is furthest away, with the view from above resembling a ^ with the knot at the apex.

Here's a gif of the stereo images :

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Geoff
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boomblurt



Joined: 18 Aug 2013
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PostPosted: Fri Sep 30, 2016 3:09 am    Post subject: Reply with quote

Aaahhh ... (/inspiration after a couple of Vodkas) ... Zerene produced a stereo with the knot off centre (to the left in the left pic and vice versa) - perhaps due to the +/- 8? Most subjects I've done wouldn't be possible at +/-8, but here, with no hairs etc to give depth cues that's what I ended up using. Then I cropped in stereophotomaker and this aspect remained. So if you compare the knot, as cropped, it is all moving in one direction.

When the images are repositioned so the knot is in basically the same place, as in the gif, the rotation around the knot is evident. Could this explain it?
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Geoff
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ChrisR
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Joined: 14 Mar 2009
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Location: Near London, UK

PostPosted: Fri Sep 30, 2016 4:23 am    Post subject: Reply with quote

These look to be flattened, once air-filled tubes, like polar bear guard hairs?

found a ref:
http://azadocents.org/wordpress/?p=211
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Chris R
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rjlittlefield
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PostPosted: Fri Sep 30, 2016 5:05 am    Post subject: Reply with quote

boomblurt wrote:
Could slabbing be the cause? The stack was 20 slabs, with about 200 images in total.

Bingo!

So, I'll bet that what you did was to add the slabs to the end of the regular source files, set stereo for +-8, then Stack Selected of just the slabs, the last 20 of the total 200.

When ZS processes Stack Selected with stereo turned on, the shifts are interpreted as applying to all the input files as a single stack. That's what allows Stack Selected outputs to serve as retouching inputs for a full stack.

But in the scenario I've outlined, it means that the shifts for the 10% of images that actually got stacked corresponded to a rotational component that was only 10% as large as you expected, plus a constant offset that accounts for the other 90% of the nominal shift. Effectively you got a stereo rotation corresponding to only +-0.8 instead of +-8.0.

A better way to do the stereo would be to either
(1) open a separate project containing just the slab outputs and Stack All those, or
(2) Stack Selected the original 180 images instead of the 20 slabs.

In either case, appropriate shifts then would be in a range of maybe +-2 to +-3, giving a stereo separation that is roughly 2.2 to 3.3 times larger than you have now. Remember that you can use arbitrary shifts, like 2.5, if that looks better than either 2 or 3.

--Rik
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boomblurt



Joined: 18 Aug 2013
Posts: 131
Location: Australia

PostPosted: Fri Sep 30, 2016 5:14 am    Post subject: Reply with quote

Interesting link, Chris. It is a guard hair, and I only mentioned polar bears as I seemed to recall from somewhere that their "white" hairs are actually clear.

And thanks Rik, that makes sense. I usually use that sort of shift so it was confusing, and I'll know in future.
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Geoff
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Beatsy



Joined: 05 Jul 2013
Posts: 707
Location: Malvern, UK

PostPosted: Fri Sep 30, 2016 5:58 am    Post subject: Reply with quote

Nice one boomblurt - your efforts paid off handsomely. I find lighting tricky at 50x too (although my hair knot had the mitty on a 135mm tube lens, so only 33.75x on the sensor - but still tricky nonetheless).

Interesting to compare the differences. I see this hair also has a flattened cross section like my beard hair - was it fairly coarse?

Perhaps we're at the start of a series here... Smile
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boomblurt



Joined: 18 Aug 2013
Posts: 131
Location: Australia

PostPosted: Fri Sep 30, 2016 6:53 am    Post subject: Reply with quote

Thanks, Beatsy Very Happy

The hair was almost as thick as a beard hair, but the cuticle scales were larger. Untied, the shape didn't seem to be too far off cylindrical (I had another look after Chris' post) - maybe the tension in the knot increases any flattening present?

And I'd wager that Chris is right and the hair is hollow, just from the way it deforms; seems lots of animals have hollow hair including some dogs.
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