Spider web "diffraction"

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LordV
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Joined: Thu Nov 22, 2007 10:28 am
Location: UK

Spider web "diffraction"

Post by LordV »

I really can't remember where this came up apart from being some time ago. Someone had a photograph with some lines of colour banding in and was asking what caused it. Think I suggested it might be spider web but didn't really have a convincing example.
Anyway came across this photo on flickr
https://www.flickr.com/photos/38628972@N05/15116370986/

Which is a very good example of the effect and is described as diffraction.
Brian V.
www.flickr.com/photos/lordv
canon20D,350D,40D,5Dmk2, sigma 105mm EX, Tamron 90mm, canon MPE-65

Craig Gerard
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Location: Australia

Post by Craig Gerard »

Brian,

Thanks for the links. Fascinating photographs.

This one too:
http://www.flickr.com/photos/38628972@N05/9740807791/


Craig
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

Chris S.
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Location: Ohio, USA

Post by Chris S. »

Yep, thanks Brian--interesting indeed.

Like you, I'd put "diffraction" in quotation marks, as I wonder if this is really diffraction, or something else. It certainly puts me in mind of the speckle one can see in the reflection off of some metal objects, if the light source has a degree of coherence.

I was just outside in the dark, examining the web of an orb-weaver with an LED flashlight. I did not find an angle from which I could see any color produced by the web. Perhaps I simply didn't find the correct angle (quite possible). But part of me thinks a requirement may be for the light to be at least somewhat coherent, which the sun can be. If so, that would be a suggestion that it's more of a speckle phenomenon.

In doing a quick search on how to harvest strands of spider silk (toward performing the obvious next step), I came across a couple of links that might interest others, as they did me.

Short video: Group at Oxford harvesting spider silk by machine

Graphic: Six types of spider silk glands, and how each type is used

--Chris

LordV
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Location: UK

Post by LordV »

I'm pretty certain I've only seen this effect in strong sunshine.
Brian v.
www.flickr.com/photos/lordv
canon20D,350D,40D,5Dmk2, sigma 105mm EX, Tamron 90mm, canon MPE-65

TheLostVertex
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Location: Florida

Re: Spider web "diffraction"

Post by TheLostVertex »

LordV wrote:I really can't remember where this came up apart from being some time ago. Someone had a photograph with some lines of colour banding in and was asking what caused it.
I can think of several threads where this topic has come up. Rik's post here seems visually close.

I too wonder if it is diffraction. Perhaps the DoF is blurring the effect so much that its messing with me. Maybe I will be able to find some co operative spiders and have a look myself.

LordV
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Joined: Thu Nov 22, 2007 10:28 am
Location: UK

Post by LordV »

Just a follow up. Looked at quite a few webs yesterday around lucnchtime in fairly bright sun and could not really see much in the way of colour effects. This morning though got the photo below shooting into a tangle web nearly directly into the low early morning sun. Certainly showing some optical effects. Camera in shutter priority no flash.
Brian V.

[url=https://flic.kr/p/oSoabJ]Image
www.flickr.com/photos/lordv
canon20D,350D,40D,5Dmk2, sigma 105mm EX, Tamron 90mm, canon MPE-65

ChrisR
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Post by ChrisR »

I THINK that's Fraunhofer diffraction, from a coherent light source.
Particles behave like similarly sized/shaped apertures, for which most of the examples appear.

Chris S.
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Post by Chris S. »

While Brian has been studying spider silk in the field, I've been studying spider silk in the macro studio. Although he and I have not collaborated, I suspect our findings are complementary.

Here is a studio (Bratcam) shot of a 30-micron-thick strand of structural spider silk, lit--similarly to what Brian described--from barely off-axis. Rather than using sunshine for light, I used a halogen illuminator and fiber-optic light guide, which--much like sunlight, can produce reasonably coherent illumination.

Image

More images to come--most likely to be posted in a separate thread.

--Chris

LordV
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Location: UK

Post by LordV »

Interesting stuff Chris !
Brian V.
www.flickr.com/photos/lordv
canon20D,350D,40D,5Dmk2, sigma 105mm EX, Tamron 90mm, canon MPE-65

Chris S.
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Post by Chris S. »

FYI,

Have continued the conversation in this post.

--Chris

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