[obol] Re: photos of new feathers - fuzzy! Diffraction or what?
- From: "Jenkins, Maurice A." <alanjenkins@xxxxxx>
- To: "priscillanhk@xxxxxxxxx" <priscillanhk@xxxxxxxxx>, OBOL <obol@xxxxxxxxxxxxx>
- Date: Sat, 27 Sep 2014 19:56:24 +0000
Hi Priscilla,
It's not clear to me what feathers and what parts of the feathers you're asking
about. The greenish iridescence is normal light diffraction of some feathers
in many species. In fact, most avian green color is from iridescence and not
pigmentation. It would seem to me that one would not be able to focus on
iridescence, just like tying to sharply focus on a rainbow.
I do not see any ensheathed feathers in your photo, they all appear to be fully
grown out. The sheaths of in-growing feathers are translucent white and round
in cross section like a white soda straw.
If the fuzzy nature you refer to is the tan edging of the feathers, they might
appear frayed out on the edges and thereby looked unfocused; the edges of some
feathers are less tightly organized (the adjacent feather filaments adhere less
to their neighbors) than the central parts closer to the shaft. The tan and
white edges of feathers are weaker than darker ones because dark pigment
(melanin) makes the feathers stronger where it occurs. Feather mites, which
eat feathers, specialize in eating away the less pigmented, and weaker parts,
which changes the shape of the feathers along the edges and would make the
eaten feathers look sharper. Many body feathers start out spade shaped with
convex edges, and as the mites eat the softer less pigmented edges, they become
lance shaped with concave edges.
That's my take on it, but again I'm not quite sure what parts or
characteristics you are referring to, and fuzziness could just be a case of
camera movement, out of depth of field parts of the photos or an artifact of
enlarging the shot.
They are great photos, however, please keep on sharing them.
Alan Jenkins
Creswell, Oregon
________________________________
From: obol-bounce@xxxxxxxxxxxxx [obol-bounce@xxxxxxxxxxxxx] on behalf of
Priscilla Nam Hari Kaur [priscillanhk@xxxxxxxxx]
Sent: Saturday, September 27, 2014 11:36 AM
To: OBOL; Priscilla Nam Hari Kaur
Subject: [obol] photos of new feathers - fuzzy! Diffraction or what?
Green Herons seem to be easy to approach this time of year.
The cropped photo in the link below was taken of a bird
only about 20-25 feet away.
The focus seems sharp across the entire patch of bird shown,
but what intriques me is the "fuzzy" appearance
of some of the very short - and I presume - "fresh" or new feathers.
A friend suggested these feathers are still encased in some kind of sheathing
or not fully opened yet, which sounds good. That makes me think
that the fuzziness is due to diffraction of light through these
hypothesized sheaths.
I should add that a bunch of photos of different Green Herons in recent
weeks show this same phenomenon in the same area of the birds,
so it's not an artifact of the camera.
Does anyone know more about any of this? I tried googling around
but couldn't find anything. I'd really appreciate knowing
a little more about what is going on here, both in terms of bird feather
physiology, as well as the photographic/diffraction aspect
(if that's what it is).
http://priscillanhk.com/images/cropped_2_IMG_5229.JPG
http://priscillanhk.com/images/cropped_IMG_5229.JPG
Thanks!
Priscilla Sokolowski
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