Well, I for one am staying the hell out of this.
MARK!
Kenneth Waller
http://www.pentaxphotogallery.com/kennethwaller
----- Original Message -----
From: "P. J. Alling" <webstertwenty...@gmail.com>
Subject: Re: Define "blown out" :-)
Well, I for one am staying the hell out of this.
On 4/5/2010 4:07 PM, David Parsons wrote:
I didn't see a question in your first post.
On Mon, Apr 5, 2010 at 3:44 PM, Jack Davis<jdavi...@yahoo.com> wrote:
I only read as far as about half of your first sentence. I didn't need to
read further as it was obvious you had missed the point of the question.
Jack
--- On Mon, 4/5/10, Godfrey DiGiorgi<gdigio...@gmail.com> wrote:
From: Godfrey DiGiorgi<gdigio...@gmail.com>
Subject: Re: Define "blown out" :-)
To: "Pentax-Discuss Mail List"<pdml@pdml.net>
Date: Monday, April 5, 2010, 12:05 PM
On Mon, Apr 5, 2010 at 10:27 AM, Jack
Davis<jdavi...@yahoo.com>
wrote:
I'll offer mine the nebulous term by saying that if at
least some surface areas are rendered featureless by virtue
of being too bright, I'd consider those areas "blown out."
Many images can tolerate a certain amount of this condition,
but it's amount is the criteria and varies with each viewer.
Said areas must, of course, contain some available mask
detail which defines the surface.
IOW, I'm not talking about an absolute ball of glare
wherein no detail is discernible.
There's nothing nebulous about "blown out". Consider areas
of pure
white with no detail as Zone 9 on the Zone System
scale defined as
follows:
Zone 0 – key black or pure black – carbon or photo
paper black.
Zone 1 – near black – shadows in faint light or rooms
without light.
Zone 2 – dark gray/black – only subtle textures are
visible.
Zone 3 – very dark gray – distinct shadow texture is
visible.
Zone 4 – medium dark gray – slightly darker “black”
skin, dark foliage
or shadows in landscapes.
Zone 5 – medium gray or 18% gray – darker “white”
skin or lighter
“black skin,” light foliage or the dark blue of a clear
blue sky.
Zone 6 – mid-tone gray – average “white” skin or
shaded areas in snow
on a bright, sunlit day.
Zone 7 – light gray – pale “white” skin, a concrete
walkway in sunlight.
Zone 8 – gray/white, near white – distinct highlight
detail, like a
white wall in sunlight or brilliant surfaces in flat
light.
Zone 9 – known as key white or pure white – pure white
paper or snow
in bright sunlight.
(Normally I think of the Zones as being from 1-10, but
Ansel was a C
programmer and did a 0-based count ... ;-)
So, by definition, anything you want detail in is "blown
out" if your
exposure has placed it above Zone 8 on the above scale.
Since I've never seen any application use 16-bit number
scales to
describe pixel values, you can determine what areas of your
image are
"blown out" in Photoshop or Lightroom using either a
percentage scale
or an 8-bit pixel value scale and floating the cursor over
white-looking areas while looking at the information
display panel.
Presuming that the exposure did not go to saturation and
there is data
in those bright areas, you can place them in adjustment
using the
Exposure (aka white point) sliders. This table makes it
easy ...
http://homepage.mac.com/godders/zone-system-numbers.jpg
EG: you have a near blown out area in a photo that you want
to ensure
images with detail on screen and in your prints. Float the
cursor over
it in Lightroom and see that it is currently at about 94%
in all
channels (or in one of them if that is the significant
color of the
area). Nudge the Exposure slider in the negative direction
until it is
in the range of about 85-88% to set that as the brightest
point. Now
make adjustments with the mid-tone, black point and Tone
Panel to
bring the rest of the photo into line with a satisfactory
display.
A certain amount of area at Zone 9 is fine, as long as it's
not where
you wanted to convey detail. Too much Zone 9 in an image
generally
looks bad. Another thing to be aware of is that many papers
and
monitor screens cannot display the full 10 zone scale very
well, or
have non-linear characteristics ... That's why calibration,
profiling
and testing for DR are essential to good quality image
display,
whether on screen or on paper.
--
Godfrey
godfreydigiorgi.posterous.com
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