David Gluckman says ?
you have to get as close as you can within the
constraints of your

lens (I need to be at least 16 feet away with my 600mm lens).?


? David is saying that the minimum focusing distance for his lens is 16
feet. (Like a pair of binoculars or spotting scope has a minimum focusing
distance). This can be further reduced, at some expense in light, by adding
extension rings to the lens. He?s accurately said that no one gets this
close with Snowy Owls.





David Gluckman says ?
. The autofocus on digital cameras uses the

lines (differences in contrast) as focusing points. On a white bird like
Snowy

Owls, finding those lines is very difficult for any camera unless you can
get

close enough. This is particularly so for the fine white facial feathers
which

become even more difficult to photograph if there is any movement caused by
the

wind. If you look carefully at the images posted you will find very few with


clear facial feathers around the beak unless they were wet or the shooter
very

close
.?



This is not a good reason to get close to Snowy Owls
as the rest of us who
use long focal length lenses have no problem with the autofocus working
accurately on snowy owl face at long distances. (40 to 200 yards is easy.
Check the exif distances on these images
(select the ?original image?
options at the bottom of the image and view the exif below it for distance,
in meters (meter is 39.7 inches), and yet no lack of detail in the dry white
face even though not very close).



http://www.pbase.com/donnelson/image/140119032

http://www.pbase.com/donnelson/image/140119038

http://www.pbase.com/donnelson/image/140119060





David is correct about atmospheric effects. Note that these are pretty
limited when temperatures are low like they are in the Northwest over the
past few weeks, although there are always exceptions. Atmospheric effects
can be a larger problem when the sun is out, with local heating of some
surfaces. Especially in the spring and summer.



Regards

Don Nelson

Oregon



Subject: Observations of a big lens photographer of Snow Owls
From: cgluckman AT aol.com
Date: Mon, 12 Dec 2011 20:27:01 -0500 (EST)

Once again the Tweeters discussion about big lens photographers is
interesting

and poses one question that I'll try to respond to. I'm sorry we had to
cancel

the photo symposium planned for December that was going to cover

bird/photograher topics so we'll just have to try for a reset next year. The


following is some information for you non-photographers who are interested
in

understanding why us big lens folks want to get so close to the birds. It's
not

meant as an excuse or reason for action, I leave that for others to sort

through.







Most bird shooters want the clearest, sharpest image they can get. In order
to

do that, you have to get as close as you can within the constraints of your

lens (I need to be at least 16 feet away with my 600mm lens). I rarely need
to

get that close (except shooting hummingbirds and sparrows), nor do I usually


want to do so because I may want the whole bird in the picture and the
larger

birds just won't fit when that close. The autofocus on digital cameras uses
the

lines (differences in contrast) as focusing points. On a white bird like
Snowy

Owls, finding those lines is very difficult for any camera unless you can
get

close enough. This is particularly so for the fine white facial feathers
which

become even more difficult to photograph if there is any movement caused by
the

wind. If you look carefully at the images posted you will find very few with


clear facial feathers around the beak unless they were wet or the shooter
very

close. In addition to focus problems, all telephoto shots are subject to

atmospheric distortion that increases dramatically with the distance from
the

object being shot, depending on numerous conditions that every shooter
should

know but many don't. Temperature differentials across water, snow, sandy
areas,

rocky shores, open fields and wooded hills can have a major impact on the

clarity of an image. Dust or fog in the air decreases clarity. Lots of
humidity

does the same. You can reduce these impacts by shooting when the air is

clearest or temperature differentials are the lowest but you can never
totally

eliminate the effects. However, you can reduce this distortion by getting

closer to the object. That's why we want to be as close as possible. This
won't

resolve the ethical/interaction problems raised but I hope it will add a bit
of

information to the discussion.







David Gluckman

811 22nd St.

Pt. Townsend, WA 98368

360 379-0360