From: Mike Unsold (mike_at_antispamdomain.not)
Date: Wed Jun 25 2003 - 11:00:49 EDT
Good test list. The only comment that I have is that IS0 3200
may not be used much in practice. Typical ISO settings in use are
200 to ~800. I would add this range of IS0 numbers to the test list.
Mike
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Thanks, this is a good starting list and a good starting point for
evaluating
the cameras. I am learning rapidly about these cameras from this
list and
your fine contributions. I will think about these issues a bit more
today and
post a response.
Regards -- Doc G
----- Original Message -----
From: Pertti Tapola
To: digital_astro_.at._yahoogroups.com
Sent: Wednesday, June 25, 2003 6:59 AM
Subject: [digital_astro] 10D dark frame comparison (was: Data point
on Canon
10D)
--- In digital_astro_.at._yahoogroups.com, "R. A. Greiner"
<ragreiner0_.at._c...> wrote:
> I think a list all in one place is important. This should include
camera model with first part of serial number, The temperature of
the
camera, the vital settings such as RAW, ISO speed, Color settings
and
processing settings in the camera, and of course the post processing
that
is done in the Canon and/or other software.
I think we will have to wait until the Canon FileViewer 16 bit TIFF
conversion
from RAW really works. Until then you need some other piece of
software
(at the moment CaptureOne) to get the real results from the image.
But FileViewer should work really soon now.
If we use the RAW format, most of the camera settings lose
significance.
White balance is decided only after the raw data has been captured,
and so are all the "parameters" (sharpening, contrast, etc).
If we use the (working) 16 bit linear TIFF conversion, there is
nothing
that interferes with the raw detector data. In this way we can avoid
the stretching done by the camera for the dark frame. (That would
favour cameras with very hot pixels over those that have uniform,
though
smaller noise.)
> This makes quite a list. Many of the variables are default
settings of
course. I have not yet found all of the settings possible. Since you
have
considerable experience with these issues, can I suggest you start
us off
with a list that you feel comfortable with.
Well, I don't think many variables remain if we use the RAW format.
So I suggest, as a "standard 10D dark frame test procedure", the
following:
1) remove the lens and put the (plastic) cap on instead,
2) cover the finder (with the cover that is integrated to the strap),
3) put the camera in shadow, anyway,
4) select the RAW image mode,
4) use ISO 3200 and 30 seconds (from the camera settings)
5) take the first image with camera that has not been used for a
while
(to remove the effect of warming of the camera electronics)
6) record the ambient temperature,
7) convert the file with FileViewer into a 16 bit TIFF, using the
linear mode
and false color filter,
8) use Photoshop to find out the average value in the image as well
as the standard deviation, one set of values for luminance and
one set for each of the colors (R, G and B), a total of eight
numbers,
9) give a verbal description of the stretched image (e.g. uniform
starlike
white noise, predominantly green speckled noise, multicolored noise
that increases to the right, amplifier glow on the left or whatever
the
image looks like).
> We can then attack it with enthusiasm. (G)
I'm looking forward to that! ;-)
> I did by the way do the testing of my two cameras at 22 degrees C
and an
ISO of 1600.
I suggested using ISO 3200 and 30 seconds, because that makes testing
simpler. Based on some experiments with my camera, it gives a good
estimate of the noise at ISO 400 and 300 seconds but it is a lot
quicker
and is also easy to perform in cases where you don't have a remote
timer
available. The time is also short enough to test in a shop or a
friends
camera.
> I think we are on the way to getting this evaluation pinned down.
I
plan, soon, to do some testing at various temperatures since I have
a
temperature chamber available. I am very interested in knowing how
temperature affects the noise. I wonder how the camera will function
at
-40C and +40C. (VBG)
Tell us, please. I will be able to tell you in January how the
camera works
in -20C. Based on real-life experiments with Nikon 990, we should see
almost no noise in even several minute exposures at ISO 3200. But
then again,
the temperature behaviour of CMOS detectors might be different from
CCD,
and also advanced Canon processing does also change it.
I tried making one experiment where I compared 20C with 10C, but I
did
not find any difference - or maybe the time was too short for the
camera
to cool down.
Pertti
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