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Posts Tagged ‘ommatidia’

You know you are pretty close to a dragonfly when you can see individual grains of pollen on its head and body. I photographed this Uhler’s Sundragon dragonfly (Helocordulia uhleri) on 12 April alongside a creek in Northern Virginia. Ideally it would be best to stabilize macro shots taken at this close a range by placing the camera on a tripod, but in a field situation with a live subject, that is rarely possible.

If you click on the individual images, you will see some wonderful details, like the ommatidia, the individual optical units that make up the amazing compound eyes of these dragonflies.

Uhler's Sundragon

uhler's sundragon

© Michael Q. Powell. All rights reserved.

 

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Dragonflies have amazing compound eyes that wrap around their heads. With up to 30,000 facets (ommatidia, to be technical), dragonflies have incredible vision and can even see colors beyond human visual capabilities, like UV light. For an easy to read discussion about dragonfly eyes, i.e. not overly scientific, check out this posting by “grrl Scientist” that was posted on scienceblogs.com.

I captured this close-up image of a Great Blue Skimmer dragonfly (Libellula vibrans) yesterday at Occoquan Bay National Wildlife Refuge. At least once a season, I manage to get a shot like this when a cooperative dragonfly lets me get close. I captured the image below with my trusty Tamron 180mm macro lens on my Canon 50D DSLR. This lens, which has a longer focal length than most macro lenses, gives me some stand-off distance so I can get a macro shot like this without actually being on top of the subject. The only downside to the lens is that it has no built-in image stabilization, so I have to pay extra attention to remaining steady when shooting with it—I generally use a monopod to help reduce camera shake and I think it helped for this image.

The image is framed just as I saw it in my viewfinder. Most of the time I end up cropping my images as part of my normal post-processing, but in this case it looked pretty good without any cropping whatsoever.

Great Blue Skimmer

© Michael Q. Powell. All rights reserved

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When I am trying to take a close-up shot of a dragonfly, I know that I have succeeded when I manage to capture some of the details of the ommatidia. What are ommatidia? Ommatidia are the up to 30,000 hexagonal facets that make up the incredible compound eyes of a dragonfly. For more information and a more scientific explanation, check out a posting entitled “Super-predators” that Sue did in June 2013 in her Backyard Biology blog.

Rather than think about science, today I would prefer to simply bask in the beauty of the blue-eyed Blue-faced Meadowhawk dragonfly (Sympetrum ambiguum) that I photographed yesterday as it perched on a fallen leaf at my favorite marshland park. The color of the dragonfly’s eyes completely captivate me.

As for the ommatidia, I’ve cropped a portion of the image and added it to the posting as a second image to make it even clearer what they look like. I chuckled a little when I examined the cropped image, because this dragonfly, like some others that I have photographed, has the sparsely distributed mustache and chin hairs that never fail to remind me of human teenagers who refuse to shave in a vain attempt to look older.

Blue-faced MeadowhawkBlue-faced Meadowhawk

© Michael Q. Powell. All rights reserved.

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