Forbidden colours: backlight spiderwebs (part 2) and more surprising finds

To prove my claim that the colours in a spiderweb can indeed be created with the sun as backlighting, I took photos of spiderwebs high in a tree, with my camera pointed dangerously close to the sun. And a new surprise finding.

[1927] Original picture (scaled to 900x600 pixels).

All of the following spiderwebs are backlight pictures high in a Juneberry (Amerikaans krentenboompje, Amelanchier lamarckii ). Because they are so high in the tree, I could not identify the spider, but presumably it is also a Garden Cross Spider (kruisspin, Araneus diadematus).

[1902]. back-lighted spiderweb. overview. contrast enhanced

[1938] Spiderweb, backlight, contrast enhanced.

 

The background is dark because the contrast in the photo was increased afterwards, making the colours stand out better. Originally, the background was very light: it is a backlit photo; the sun was dangerously close to the spiderweb.

Here is a unedited photo which looks to me like an impressionistic painting: 

[1864] Out of focus results in an impressionistic painting!

 

[1864] detail. contrast slightly enhanced

Surprising finds

The typically feathery pappus of a ripe thistle flower is known as thistle-down. The feathers make the seed airborne with the slightest breeze. The feathers are lightweight and thin by design: they are supposed to be blown by the wind. I found somewhere that the individual hairs can produce colours, and indeed that's what I found too. They look very similar to the colours of spiderwebs! 

 

[5586]. Seed with feathers.

 

[5580]. Same object. Note colour patterns similar to spiderwebs!
Slightly post-exposure enhanced contrast.

Artificial objects

 

[5559]. Snap Ball Tea Strainer (without sunshine)

 

[5573] Same object with sunshine (detail)
Out-of-focus enhances the effects.
No post-exposure editing.

[5573] Unexpected black concentric circles! (detail)
No post-exposure editing.

[5576]. image 2x magnified.
Surprise: 5 black concentric circles! Wow!

 

[5573] Detail. some look like parts of spiderwebs?

 

So, artificial and natural objects exhibit at least some comparable patterns. Does this invalidate my hypothesis that spiderweb threads have an internal banded structure? and that everything has to be explained by the laws of optics? Are they visual illusions? However, are the colour patterns really similar enough? 

We can safely assume that the artificial metal objects have no internal crossbands. So, the optical phenomena are not caused by internal structures of the metal. They must be optical effects. But spiderwebs and the feathers of seeds are composed of proteins and possibly other biological compounds. Could that make a difference? These questions are far outside my own expertise and technical capabilities. I wonder if physicists recognize these patterns, especially those black concentric circles? I included them in my blog because they are so wonderful.

 

 

Technical details

Spiderwebs: SONY RX10-iv. 

Macro (Snap Ball Tea Strainer; seed): SONY A6700/90mm macro. Sunlight.

 

Previous blog

• Spiderweb colours violate the rainbow rule 28 July 2026

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