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!
All colours are real colours, not enhanced!

 

[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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Solar eclipse 12 August 2026 in The Netherlands captured with digital camera equipped with Neutral-density filters

SONY RX10-iv 600mm ISO200 f/4 1/15 sec. time 20:02
that is about 8 minutes before maximum
Dimensions of the sun on this image: 780x725 pixels
Original image: 5472x3648 pixels.

The solar eclipse 2026 was a total eclipse in Iceland and Spain, and partial in The Netherlands. The weather was perfect, completely cloudless, but a littlle bit too hot at first. The maximum was around 20:10 in the evening, with 90% coverage. Because the sun was low on the horizon, a location was required with a good view to the West without trees or buildings, in this case a nature reserve (Westbroekse Zodden). The last contact was around 21:03 and sunset at 21:10.

At a previous solar eclipse I used an improvised method to photograph the eclipse. This time I used photographic HOYA PROND EX - ND500 filters. These are Neutral-density filters (ND filters) which reduce the intensity of all wavelengths of light equally, giving no changes in hue of color rendition. The filters can be combined. To ensure that the camera sensor would not be damaged, I used two of them on top of each other (1) and on top of the standard UV filter. Still, I didn't dare photograph the beginning of the eclipse and waited until the maximum. 

Manual focus required (∞). I used diaphragm f/4,0 because higher settings didn't work well. I used the SONY RX10-iv with maximum zoom 600mm, see pictures. I succeeded in making a few sharply focused photos but I stopped at the moment the sensor seem to produce distorted images. Luckily, it turned out afterwards that the sensor was not damaged! 

©A.B.

Subjectively speaking, the eclipse at the moment of the maximum coverage of 90% was somewhat disappointing; it didn't get really dark. However, the colors in the landscape did fade noticeably, and it became less warm. The human side: people came together from all over to admire the eclipse at the hospot I had chosen. It was a social happening. There was a cheerful and friendly atmosphere.

©A.B

Next solar eclipse: 2 Aug 2027 (49%).

 

Notes 

1. Warning: don't tighten the filters too much! I couldn't get mine apart anymore! I eventually managed to get mine loose again after all. One ND500 filter equals 9 stops down. Two of them equals 18 stops down! So I have used more than recommended ND100.000 (16.6 stops) and coud have easily made pictures of the start of the eclipse. See for table ND filters and stops: Fotograferen met filters and Zonsverduistering fotograferen: de complete gids voor 12 augustus 2026. I only found this website after the eclips.

 

Previous blogs

• Zonsverduistering fotograferen met een gewone digitale camera? Het kan! (29 maart 2025) Solar eclipse with standard digital camera. 31 Maart 2025
• Maansverduistering Maandag 21 januari 2019. Lunar eclipse.  21 Jan 2019
• Totale maansverduistering maandag 28 september 2015 groot succes ondanks slechte weersvoorspellingen. 28 Sep 2015

Spiderweb colors violate the rainbow rule

Spiderweb (overview). Backlight [1]

According to the laws of physics, rainbows caused by sunlight always appear in the section of sky directly opposite the sun [2]. Here I show that spiderwebs violate this rule by pictures of spiderwebs with backlight resulting in rainbow-like colors as well.

Kruisspin / Garden Cross Spider / Araneus diadematus 

Detail. length ~ 1 cm / 0,4 inches

Straight white lines demarcate a sector of the spiderweb circle
that lights up selectively. The rest is faintly visible and colorless.
The lines meet at the center of the web,
and seem to point towards the sun.

detail of previous picture. Click to enlarge.

So the part of the spider web circle that lights up seems to be a segment which points to the sun [3]. Furthermore, as shown in the previous blog, the threads of the web consist of many small segments with different colors. Contrary to the previous blog, these pictures are taken towards the sun. The fact that colors are seen at all contradict the physical rules for the formation of a rainbow by the sun. A possible explanation could be that the spider web threads are not made up of water droplets but of proteins...   

Garden Cross Spider
This little spider had nothing to eat for a week.
Finally she caught a fly! Enjoy your meal!
Note the difference in size!

An adult Garden Cross Spider
built its web on the window of the barn door.
Fortunately we could still use the door!
By the way: this location is perfect to investigate the effect
of different directions of the sunlight
because you can move the door without damaging the web!
Addtionally you can photograph the web from both directions!

 

Notes

1. The main light source, the sun, is behind the spider, facing the camera and photographer. Note: in Dutch this is called 'een tegenlicht opname'.
2. Thanks Rolie Barth and Matt Young for pointing this out. See for example wikipedia article Rainbow.  
3. However, I did not investigate this effect systematically!

Previous blogs

• Accidental discovery of the ultra finestructure of the web of the Garden Cross Spider [+additional pictures].  29 June 2026
• Araneus diadematus. Panda's Thumb Photography Contest. July 27, 2026

Links

• Spider web colorations on Youtube (high quality photographs, much better than mine!)
• Glistening spider silk with beautiful pictures of Dietrich Zawischa

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