This is the ceiling of the Longwood conservatory Organ Room. Yes,
there is some pin-cushion distortion, noticeable in this thanks to all
the straight lines (the ceiling was flat). On the other hand, this is
my "cheap" $400 consumer-grade 28-135 IS Zoom lens. I have been
considering replacing this with the 24-105mm IS "L" lens. I did not
attempt to correct this distortion problem in software, so I don't
know how effective that would be. I can say that I'd be really annoyed
if I had spent the money for an "L" lens and ended up with the same
issue.

JD
Canon 10D
EXIF Data Included
e-mail: blissful-wind(at)usa.net

Additional images at;
http://www.flickr.com/photos/john-pa/

John - Pa. wrote in :

All of these are very good shots. What is HDR? Is that combining 2 shots one
exposed for highlights and one for shadows? Or (prolly) something more
complicated. Thanks for posting these.

Jeff

Thanks for you comments.

And now you asked a question and got me started. :-)

HDR stands for High Dynamic Range. I guess you could describe
it broadly as a generic digital manipulation technique, and there are
several flavors. Basically however, it takes several images of the
same thing which have been exposed differently, and then blends them
together. In this way, for example, you can get the highlight detail
available in an EV-1 underexposure and combine it with the shadow
detail available in an EV+1 overexposure. There are other blending
techniques available to overlay and manually "paint" one image through
another, but HDR is a more automated way to do sort-of the same thing.
Sometimes people generate results with HDR that are quite bizarre and
"surreal" looking, but I'm personally more interested in trying to get
at results that IMO approximate the natural dynamic range of the human
eye, which is far broader than either film or 12-bit color depth
digital sensors can deliver.

I believe that Adobe Photoshop has a basic HDR function built in, but
I use a standalone software product called Photomatix. One of the cool
things that Photomatix can do is take these several differently
exposed images and generate a file that uses floating-point digital
values rather than fixed-bit color depth. I think of this as "true"
HDR because the color depth in this case is essentially infinite. Of
course, since neither today's printers nor monitors can directly
handle floating-point images, you still have to convert it back to at
least a 16-bit representation.

Some of the tricks for good HDR are; a) Use a tripod and a static
subject, because any displacement of subject across the several images
will show as blur after the blending; b) use aperture priority mode,
because if the different exposure settings are achieved with different
lens openings, the DOF variance will also cause distortion; c) Use
automatic exposure bracketing, if your camera has it.

JD


On Tue, 20 Mar 2007 22:32:09 GMT, Jeff Dave Wolf
wrote:

John - Pa. wrote in :

All of these are very good shots. What is HDR? Is that combining 2 shots one
exposed for highlights and one for shadows? Or (prolly) something more
complicated. Thanks for posting these.

Jeff
Canon 10D
EXIF Data Included
e-mail: blissful-wind(at)usa.net

Additional images at;
http://www.flickr.com/photos/john-pa/