Posts Tagged ‘natural science’

Frogs alive!

February 28, 2013

Frogs alive!” was recorded live on 25 February 2013 at Huntley Meadows Park, Fairfax County, Virginia USA.

Copyright © 2013 Walter Sanford. All rights reserved. www.wsanford.com

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Dragonflies in Flight

February 20, 2013

Dragonflies in Flight” is a slideshow featuring 68 still photographs by Walter Sanford. (Hey, that’s me!) The soundtrack is the song “Fly Away” by Lenny Kravitz (3:41 min).

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Tech Tips: The still photographs were adjusted using Apple Aperture and exported as 16-bit TIFFs. The TIFFs were imported into Adobe Photoshop Lightroom 4 as a collection. The “Slideshow” module in Lightroom was used to create and export the slideshow (56 MB). Watch Adobe TV and learn how to use Lightroom 4 to create a slideshow with music: “Publish a Slideshow,” by Julieanne Kost. See also, Stop-action photography of dragonflies in flight.

Copyright © 2013 Walter Sanford. All rights reserved. www.wsanford.com

Green-winged Teal (male, female)

January 29, 2013

A couple of Green-winged Teals (Anas crecca) spotted during a photowalk at Huntley Meadows Park, Fairfax County, Virginia USA. The male is shown in Photos 1-2; the female in Photo 3.

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Tech Tips: BorderFX, a free plug-in for Apple Aperture, was used to add a text watermark to the photos.

Copyright © 2013 Walter Sanford. All rights reserved. www.wsanford.com

Stop-action photography of dragonflies in flight

January 27, 2013

It is estimated a dragonfly flaps its wings at about 30 beats per second. I shot several photos of a dragonfly in flight using a shutter speed of 1/1,300 second. Turns out that shutter speed was a little too slow to stop wing motion completely.

I posed the following question to Phil Wherry, my good friend and technology/photography guru: How fast would the camera shutter speed need to be in order to freeze all motion of a dragonfly in flight? Phil’s answer is as follows.

To freeze all motion? Infinitely fast. Even if your exposure is one-millionth of a second long, the wings are going to move a little bit during that interval.

You’re going to get some motion no matter what; the question is simply how much is tolerable. At some point the motion will be small enough that the image will look sharp to you. (This same principle, by the way, applies to depth of field: Focus is only perfect at a single plane no matter what the aperture, but the “depth of field” defines the area where the error is small enough that it’s not obvious.)

We’ll start by considering a simpler scenario. Let’s say you have a motor that makes one full rotation per second. Let’s also say you take a paper plate and draw a thick black line on it, then attach that to the motor shaft. Now you have something that looks a bit like a one-handed clock, with the “hand” making one full rotation every second.

Now, let’s say you point your camera at this setup. If you take a one-second exposure, the “hand” will rotate once during the exposure; clearly you’ll have a lot of motion blur. If you shoot at 1/4 second, the “hand” will traverse just one-quarter of the circle. Shoot at 1/100th of a second, and you’ll get a little bit of motion blur as the “hand” swings through 1/100th of a circle. If you shoot at 1/1,000th of a second, there’s still some motion blur but it’s probably not enough to make you perceive the result as blurry.

Now let’s consider the motion of the dragonfly’s wings in detail: If the wings are beating 30 times per second, that means the wing goes through one complete cycle of its motion 30 times per second. Let’s say for a moment that you shoot a picture at 1/300th of a second. This is ten times as fast as the wings are beating, so you’ll capture 10% of the range of motion. At 1/1,300th second, you’re capturing 30 / 1,300 (or about 2.3%) of the wing’s beat cycle.

This is made more complicated because the wings aren’t moving at a uniform speed; they accelerate and then slow down, reverse direction, accelerate, etc. The result is, as one might expect, roughly sinusoidal in shape (though not exactly; see the blue line in Fig. 2 of “Dragonfly Flight“).

If that 1/1,300th of a second exposure happens to occur when the wings are at the end of their travel and beginning to reverse direction, very little motion will occur and the image will look sharp. If the wings are mid-stroke, then some 1/1,300th of a second is likely to have some motion blur.

Experimentation is really the only way you’ll figure this out. Flash might help, too, since a major contributor to the overall exposure would then be a pulse of light that’s only a fraction of a millisecond long.

Phil

The following photos illustrate the relationship between shutter speed and stop-action photography of dragonflies in flight: Photo 1 of 2 was shot using an aperture of f/5.2 and a shutter speed of 1/200 second; Photo 2 was shot at an aperture of f/3.8 and a shutter speed of 1,300 second.

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Copyright © 2013 Walter Sanford. All rights reserved. www.wsanford.com

Great Blue Skimmer dragonfly (female, oviposition, in flight) redux 2

January 25, 2013

The following photo gallery shows a female Great Blue Skimmer dragonfly (Libellula vibrans) laying eggs by the process of oviposition. The dragonfly skims the water repeatedly, picking up drops of water that are used to flick fertilized eggs toward the shore. The process typically lasts a few seconds to a few minutes.

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Habitat: Huntley Meadows Park, Fairfax County, Virginia USA.

Tech Tips: The photo was shot using an aperture of f/3.8 and a shutter speed of 1/1,300 second. The shutter speed was a little too slow to completely stop the motion of the dragonfly’s wings. BorderFX, a free plug-in for Apple Aperture, was used to add a text watermark to the photos.

Copyright © 2013 Walter Sanford. All rights reserved. www.wsanford.com

Common Whitetail dragonfly (immature male)

January 21, 2013

A Common Whitetail dragonfly (Libellula lydia, Plathemis lydia) spotted during a photowalk at Huntley Meadows Park, Fairfax County, Virginia USA. This individual is an immature male. As a young male the dragonfly’s abdomen will be covered by white pruinescence, hence its common name, “Common Whitetail.”

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Tech Tips: BorderFX, a free plug-in for Apple Aperture, was used to add a text watermark.

Copyright © 2013 Walter Sanford. All rights reserved. www.wsanford.com

Fall foliage at Huntley Meadows Park

December 26, 2012

Fall foliage at Huntley Meadows Park, Alexandria, Virginia USA.

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Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com

Happy Holidays!

December 25, 2012

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Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com

Ruby-throated Hummingbird: Noise reduction using Aperture 3 versus Lightroom 4

December 14, 2012

The following photo of a Ruby-throated Hummingbird (Archilochus colubris) was post-processed using Apple Aperture 3, including adjustments for noise reduction and sharpening.

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The same photo was post-processed using Adobe Lightroom 4, including adjustments for noise reduction and sharpening.

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Although neither photo is high quality, the noise reduction adjustment in Lightroom is clearly superior to Aperture.

Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com

Ruby-throated Hummingbird: Noise reduction using Lightroom 4

December 12, 2012

I used my Panasonic Lumix DMC-ZS150 superzoom camera to shoot the following photo of a Ruby-throated Hummingbird (Archilochus colubris) at the Visitor Center, Huntley Meadows Park.

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Tech Tips: The following camera settings were used for the preceding photo (above): Shutter Priority mode; ISO 800; focal length 108mm/600mm (35mm equivalent); 0 exposure value (ev); aperture f/5.2; shutter speed 1/1,250 sec. The camera automatically increased the ISO to 800 in order to compensate for less light reaching the camera sensor at a faster shutter speed. The resulting photo appears underexposed and is noticeably “noisy” (see Photo 2 of 2). I used Adobe Lightroom 4 to adjust the original photo, including noise reduction and sharpening (see Photo 1).

Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com


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