I think Fred has managed to express it better than I did.
The breast feathers in the robin are overlapping fan shaped structures. If you think of a paper fan as sort of a model for what they look like, the barbs are the ribs and the barbules are the paper connecting them. The feathers overlap and lay on the breast of the bird to keep it warm (and obviously for display purposes.) Not only in my robin photo, but in many a bird photo over the past few years, I've seen this kind of atrifacting. The combination of the way the lens resolves the image (low res/good edge detail) leads the digital camera to render the image sharpened so the barbs are prominent, but the rest is all but lost. Subjectively, it looks goods - unless you think about or have seen a lot of birds.
Of Fred's links -
http://www.ummz.lsa.umich.edu/birds/Anatomy/feathers/feather_parts.html
I spent several happy years (too many years ago to recount) working for the Museum of Zoology (and the other affiliated museums) in Ann Arbor - it's always a trip down memory lane to re-visit their web site. I should of looked at the bird collection more closely while I was there!
- MCC
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Mark Cassino Photography
Kalamazoo, MI
www.markcassino.com
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----- Original Message ----- From: "Fred" <[EMAIL PROTECTED]>
To: "Godfrey DiGiorgi" <pentax-discuss@pdml.net>
Sent: Wednesday, February 23, 2005 1:47 PM
Subject: Re: Opinions about Tokinas (Was Sigmas)
That lens has done an *excellent* job of capturing the breast feathers' structure. I used to keep birds (parrots mostly) and that's what their breast feathers look like when seen close up. Robins are much the same.
Well, I'm not so sure...
http://trc.ucdavis.edu/mjguinan/apc100/modules/Integument/hair/feathers2/feathers5.html
http://www.peteducation.com/article.cfm?cls=15&cat=1829&articleid=2776
http://www.ummz.lsa.umich.edu/birds/Anatomy/feathers/feather_parts.html
I think that the photo is showing the barbs but not the barbules, and (as mark has suggested) has sort of "sharpened" the barbs to provide a high ~apparent~ detail without actually showing the detail.
Fred
