Dashing in Blue

6 May 2013 by Paige Brown, posted in Uncategorized

The blue dasher, or Pachydiplax longipennis (meaning long wings), is a prize for macro photographers. With its beautiful colors, graceful poses and metallic eyes, what photographer wouldn't love to be able to creep up close enough to get a "bugs-eye" view of these abundant creatures?

Also known as "blue pirate", this dragonfly contributes to pest control by consuming hundreds of smaller insects every day. I didn't even know dragonflies at bugs until I caught one in the act on camera!

Dragonfly eating a bug. http://paigesphotos.photoshelter.com/.

I was likely taking pictures of female blue dashers today around the rose-bush in my neighbor's yard, as the males usually hang around swamps and water edges. The female's eyes are reddish brown in the top portion, and blue-grey in the bottom portion, as seen in the image above.

The blue dasher can be seen from southern Canada south through Mexico and Belize, the Bahamas and Cuba (Rosser et al. 2006).

Some other interesting facts:

  • "Dragonflies can fly over 30 mph (48 km/h) and can even fly backwards." link
  • "Nearly 30,000 lenses make up the compound eye, giving the adult dragonfly a 360-degree field of vision." link.

The compound is amazing to me. GrrlScientist wrote an amazing blog post about the compound eye of the dragonfly in 2009:

"All dragonfly species have excellent vision. Each compound eye is comprised of several thousand elements known as facets or ommatidia. These ommatidia contain light sensitive opsin proteins, thereby functioning as the visual sensing element in the compound eye. But unlike humans, day-flying dragonfly species have four or five different opsins, allowing them to see colors that are beyond human visual capabilities, such as ultraviolet (UV) light. Together, these thousands of ommatidia produce a mosaic of “pictures” but how this visual mosaic is integrated in the insect brain is still not known."

Each facet of the dragonfly's eye contains special (and unique) light-sensitive proteins called opsins. The top portion of the dragonfly's eye has proteins that capture shorter wavelengths of light, such as UV light, while the lower portion of the eye has proteins that capture longer wavelengths of light.

Each facet of the dragonfly's eye 'sees' in only one direction, but the combination of nearly 300,000 lenses allow the dragonfly to see in nearly all directions. Engineers including UC Berkeley's Luke Lee have actually used the dragonfly eye as an inspiration to create super-structures of tiny crystalline lenses that can collect light from all directions:

"Tests have shown that the compound eyes created by the Bio-Poets group can, in fact, detect light signals coming from virtually all directions -- better than the best fish-eye lenses of today's cameras, Lee said. They can also swiftly detect moving lights as they pass from one lens to another across the smallest distances -- an extremely useful ability, he suggested, for covert surveillance devices."

Which brings me to how I captured the images of these blue dashers - not an easy task from an optics perspective on its own! Here was my set-up:

  • Canon Rebel t3i
  • Canon 100mm Macro lens
  • 25mm auto-focus extension tube + 12mm auto-focus extension tube. These tubes are exactly what they sound like - simple hollow tubes that extend my macro lens from the body of my camera. They contain no glass or fancy optics, but simply move my lens further away from my camera's sensor. By doing so, the extension tubes decrease the minimum focusing distance of my lens, allowing me to get closer to my subject and thus increase the magnification of my lens on its own. An extension tube increases lens magnification by an amount equal to the extension distance divided by the lens focal length.
  • An simple on-camera stand-up flash, with a special light modifier. The light modifier is required because, with a direct flash, my lens could actually cast a shadow on my subject (because I have to be so close to the subject to get a picture of compound eyes!). But the light modifier can effectively bounce the light of my flash unit downward, while also bouncing and diffusing the light into different directions so that I don't cast any harsh shadows on the subject with my long lens.

Here is a picture of my set-up:

A nifty and "cheaper" way to get extreme-close ups of insects without an expensive devoted macro-photography flash device. As you can see, the "snoot," which has a white side that faces down toward the camera, will bounce the light from my flash downward onto a subject right in front of my lens. By extending the 100mm macro lens away from the camera body with extension tubes, I can get around 1.6x magnification!

I'm just happy to have caught a blue dasher in action, compound eyes and all. I'm just impressed that she let me creep up on her with this huge camera set-up!

Thanks for reading! If you are interested, my extreme close-up bug shots are for sale at http://paigesphotos.photoshelter.com/!

http://paigesphotos.photoshelter.com/

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