Re: why is 32 bit image setting making such a difference?
- From: "AB Sauers" <ab@xxxxxxxxx>
- Date: Sat, 26 Apr 2008 13:25:36 GMT
"David Weinshenker" <daze39@xxxxxxxxxxxxx> wrote in message
news:fuue9g$mju$1@xxxxxxxxxxx
AB Sauers wrote:
With the latest Photoshop's ability to work somewhat with 32 bit images,
as
an experiment, I decided to convert all planetary 8 and 16 bit images I
had
from the past to 32 bit, apply unsharp masking and see what would happen.
To my surprise, these converted images seem to be able to take, in some
cases, quite a bit more sharpening at 32 bit before noise and highlights
become problematic. In fact, I have been able to significantly clear up
several images simply by converting from 8 bit to 32 bit and then unsharp
masking carefully. My question is, why is this? I always figured that
once
an 8 or 16 bit image was saved that converting up to a higher bit was
just a
waste of space and of no benefit, but yet I am seeing results.
Even if the original camera data is 8 or 16 bit, the higher resolution
enables
the image processing calculations to work at higher resolution, so the
output
data can contain pixel levels intermediate between the quanta of the input
image.
The former version of Photoshop, and indeed this version, favors working
with images in 16 bit format, so 16 bit is what I got used to. Then when I
saw that the latest version has limited, but still useful, capabilities in
32 bit mode, I decided to just convert several 8 and 16 bit masters to 32
bit and try unsharp mask and a few other things. I was certainly surprised
by how much more sharpening I could do without introducting artifacts or
noise as I would at 8 bit and even 16 bit mode.
I decided to take a look at the histogram. At 8 and 16 bit, the histograms
of the masters basically fills the range but upon re-examination after
conversion to 32 bit, much of the range is now compressed at the left. This
extra "room" must be responsible for allowing more sharpening/ processing
routines. Once I am finished processing at 32 bit, I resave at either 16 or
8 bit, and the result is still much better than if I had never upconverted
for processing.
Now the question becomes that since most of my AVIs were in 8 bit format
(webcam), would there be an advantage to converting the individual AVI
frames from 8 bit to 32 bit mode for reprocessing (aligning, stacking, etc)?
AB
-dave w
.
- References:
- why is 32 bit image setting making such a difference?
- From: AB Sauers
- Re: why is 32 bit image setting making such a difference?
- From: David Weinshenker
- why is 32 bit image setting making such a difference?
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