Saturday, November 11, 2006

The Bird on Shipshape, on the Nest, and CCD Artifacts

The color of the bird's head in this photo taken November 7th, really made me wonder exactly at which hawk I'd been looking earlier in the day. I'm used to the wonder of hawk feathers changing rather radically depending on the light but this was extreme. Had it been Lola after all?

This photograph was taken a few moments after the one above. There was no switch made. With the number of people at the Hawkbench, we would have noticed without a doubt.
The bird is Pale Male in two photos taken in bad light November 7th, 2006.

Photograph by Lincoln Karim
This is a photograph identified by Lincoln on his site as Lola in The Ramble.

This is the naked eye view of Shipshape from the spot where the falcon photographs was taken.
At this distance and particularly if an image is backlite when digiscoping there is a tendencey towards a blue purple aura.

A reader wrote,

"The bird perched on the corner looks large. Are the Rufous back and blue wing ccd artifacts? Great sighting! Wish I could've been there. "

As this reader did with a bit of whimsy, some of you may have noticed that the "Peregrine" on the antenna of Shipshape in the entry of 11/07/2006, is a very strangely colored Peregrine. She is crow sized or I never would have seen her go behind the building, and does have the black head and thick black "mustache" of a Peregrine as opposed to the slighter mustache and paler head seen on Kestrels. I give it to you, Kestrels do look more the color of the bird in the photographs when it comes to back and wing.
Though their bellies are not nearly that rufous usually but have more of a blush on cream at the top. Also in not one of the photographs did the bird look to have a rufous tail, which it should were it a kestrel. Nor did any of several experienced bird watchers who came by the Bench while she was there and looked through the scope, dispute the general consensus. Were we all deluded? Fooled? Maybe. The whole thing is weird.

Well, I knew a weird color phenomena and even the appearance of strange shapes was something that digital cameras tended to do sometimes. And my baby Nikon, larger more advanced models don't fit the scope attachment, does it particularly when subjected to creating images with the contributing factors of low light, distance, and shooting through the magnification of the scope. I wasn't aware of what it was called. Now after the reader's question and looking it up to make sure we were talking about the same thing, I know the phenomenas name, CCD artifacts.

CCD stands for charged-coupled device. A device made up of semiconductors arranged in such a way that the electric charge output of one semiconductor charges one next to it.

Artifacts in this case are things you didn't see in the first place but appear in the photograph due to chip defects, bad pixels, cosmic rays, or including possibly, an enhancement function of my camera or computer program that makes the photograph "better" before I ever see it. But why better in that particular way?

Is the camera picking up some underlying pigment and then amplifying it? Maybe. Look at the photo of Pale Male from the same day. Do you see how dark his head is? When I downloaded the photos of the two birds from tuesday, PM and the Peregrine, I really began to second guess myself. I began to wonder if I hadn't been looking at Lola and a Kestral but had misidentified both in the field. I brought up some past photos of Lola and as I remembered, her bellyband is much more distinct than Pale Male's. Look at the bellyband in Tuesday's photos, it isn't nearly as broad or contrasting. It is Pale Male.

Whew, that was a relief. As all I've really been looking at when it comes to birds in the last good number of years has been Red-tails and particularly Pale Male and Company. To mistake Lola for Pale Male would have been dreadful.

Donegal Browne


Anonymous said...

Is it possible that a female Kestral could have that plummage?

Donegal Browne said...

6:06 Anon,

Supposedly a female Kestrel lacks the blue-gray wings. If Kestrel he was male.

By naked eye the colors in the photograph were not really apparent. I've been giving thought to the hypothesis, that pigment registered by the camera, was then enhanced by some aspect of the photo process, at which point the camera told us it actually may have been a Kestrel. Something all our eyes couldn't see, hampered by distance, glare, and the idiosyncracies of high magnification. .

Anonymous said...

The color cast problems you have digiscoping are not CCD artifacts. It is an optical problem common with digiscoping, called Chromatic Aberration. It results in Blue/Purple fringe problems at the edges of objects.

CCD artifacts are a minor problem with digital cameras. Chromatic Aberration and JPEG artifacts (problems with compression which result in a loss of detail and similar problems to Chromatic Aberration) are your issues here.

The bird is a Kestral. Tail shape, body shape, head markings, and lack of eye ring all point to a Kestral.

Donegal Browne said...

Yes, I agree we were fooled in the field.

I'll post a photograph that shows what we were seeing at the highest magnification of the scope before the images were brought home and further enhanced.

I also think after going back to previous photographs of the GM Peregrines that this Kestrel doesn't sit in the kind of postures that those did and it was a cue I missed.