"16-bit" mode.

writes:

I have no idea whether he has any skill as a photographer, but the
comments I've seen him make on theoretical concepts are totally
clueless. He's not quite as deluded as The Preddiot, but he's in the
same weight-class.

I'd have to disagree with that. I had a number of long drawn-out
arguments with Timo in this newsgroup several years ago, but I have to
say that The Preddiot is worse.

Timo is pretty firmly convinced of his own rightness, and tends to
disparage the personal integrity of anyone who disagrees with him. But
if you argue with him in minute detail about something he says that is
clearly wrong, he will eventually see that. He'll never say "I was
wrong", but he will abandon wrong positions eventually if you prove
he's wrong. It just isn't worth the work to do so.

Timo does care about telling people the truth; it's just that he's
sometimes wrong and it's incredibly hard to demonstrate that to his
satisfaction. He's also put a lot of time and effort into thinking
about image processing and setting up his pages; it's too bad they are
sometimes misleading.

But "George Preddy" just makes ridiculous statements, with no reasonable
argument to back them up. And he won't support what he says - he
ignores questions from other people. He's effectively an output-only
device with no regard for the truth at all. Nor does he seem capable of
much original argument; he mostly just parrots Foveon marketing hype.

Dave

writes:

I have no idea whether he has any skill as a photographer, but the
comments I've seen him make on theoretical concepts are totally
clueless. He's not quite as deluded as The Preddiot, but he's in the
same weight-class.

I'd have to disagree with that. I had a number of long drawn-out
arguments with Timo in this newsgroup several years ago, but I have to
say that The Preddiot is worse.

Timo is pretty firmly convinced of his own rightness, and tends to
disparage the personal integrity of anyone who disagrees with him. But
if you argue with him in minute detail about something he says that is
clearly wrong, he will eventually see that. He'll never say "I was
wrong", but he will abandon wrong positions eventually if you prove
he's wrong. It just isn't worth the work to do so.

Timo does care about telling people the truth; it's just that he's
sometimes wrong and it's incredibly hard to demonstrate that to his
satisfaction. He's also put a lot of time and effort into thinking
about image processing and setting up his pages; it's too bad they are
sometimes misleading.

But "George Preddy" just makes ridiculous statements, with no reasonable
argument to back them up. And he won't support what he says - he
ignores questions from other people. He's effectively an output-only
device with no regard for the truth at all. Nor does he seem capable of
much original argument; he mostly just parrots Foveon marketing hype.

Dave

Mike Engles writes:

He did in 1998 and all the articles are on his site.
He certainly is a proponent of linear processing.
ftp://ftp.alvyray.com/Acrobat/17_Nonln.pdf

The thing he doesn't really address is that you don't need to *store*
data in a linear encoding in order to *process* it in a linear space.

Choosing nonlinear storage but linear processing has its costs (the
conversion steps), but choosing linear storage also has its costs (more
bits on disk or in memory for the same intensity range and resolution).

Dave

Chris Brown wrote in message ...
In article ,
Toby Thain wrote:
Chris Cox wrote in message
.. .

The color mode doesn't matter - it's still 16 bit data (0..32768).

It's deceptive to characterise that range of values as "16 bit" - it
has only 15 bits of dynamic range.

YM precision. Dynamic range is independent of the number of bits used to
represent an image.

Right. Sloppy of me.

Chris Brown wrote in message ...
In article ,
Toby Thain wrote:
Chris Cox wrote in message
.. .

The color mode doesn't matter - it's still 16 bit data (0..32768).

It's deceptive to characterise that range of values as "16 bit" - it
has only 15 bits of dynamic range.

YM precision. Dynamic range is independent of the number of bits used to
represent an image.

Right. Sloppy of me.

Chris Brown wrote in message ...
In article ,
Toby Thain wrote:
Chris Cox wrote in message
.. .

The color mode doesn't matter - it's still 16 bit data (0..32768).

It's deceptive to characterise that range of values as "16 bit" - it
has only 15 bits of dynamic range.

YM precision. Dynamic range is independent of the number of bits used to
represent an image.

Right. Sloppy of me.

Mike Engles wrote:

Dave Martindale wrote:

Mike Engles writes:


What I have just read chimes with everything I think should happen in
digital imaging. It does completely contradict everything that has been
written about gamma encoding in these and other forums with the
necessity for gamma to maximise the use of available bits.

ftp://ftp.alvyray.com/Acrobat/9_Gamma.pdf

Yet this guy seems to be a pioneer of digital imaging.

First, note that the article was written nearly 10 years ago. Since
then, we have the PNG file format that explicitly tells you what
non-linear transformation was used in encoding the image. We have
colour management systems, with data chunks encoded in a file header
telling you even more about the meaning of the data. And I think that
even in 1995 TIFF would let you describe the data nonlinearity.

He's right that a lot of guessing happened in 1995. But things are
better now. He also talks a lot about one particular application,
Altamira Composer, which apparently assumes PC monitors have a gamma of
1.8 (with the participation of the lookup table in the hardware). To
the best of my knowledge, this value has never been common on PCs, only
on Macs, so one could describe this as simply a bad assumption for PC
software.

Anyway, it's now perfectly possible to *store* images using a nonlinear
encoding, but unpack them to a wider linear representation before doing
arithmetic on them, then convert back to the nonlinear representation
for storage again. He recommended linear storage because that avoids
conversion operations, and avoids having to store the data to describe
the nonlinearity, but that's not necessary to do linear arithmetic.

Unfortunately, the memo does *not* discuss the cost of linear storage.
It's a simple fact that if you store 8 bits per component (i.e. 24 bit
colour), 8-bit linear coding does not provide sufficient intensity
resolution to code shadow areas without quantization artifacts. 8-bit
"gamma corrected" encoding is used because it provides more resolution
in the shadows, where it's needed, and less in the highlights, where the
steps are still small enough not to see. To use linear coding without
quantization problems, you'd need 12 or better yet 16 bits per
component, and most applications do not want to pay the extra price in
file size for no visible benefit.


Also why is image data from spacecraft and astronomy not gamma
encoded.It is after all digital photography. They must be transmitting/
recording in at least 18 bit. That is the bit level that Chris Cox et al
say is the minimum necessary for linear images, without gamma encoding.

First, the data from those sources is quantitative data used to make
actual measurements of intensity. Producing pretty pictures is somewhat
incidental. So it's worth providing a wide linear data path, and
calibrating the whole thing periodically, in order to get numbers that
mean something. But consumer cameras are not used as photometers, so
the same level of accuracy is not needed.

As for how many linear bits are needed to equal 8 bits gamma encoded: it
all depends on the brightness range you want to represent. 16 bits is
pretty damned good.


It does seem that what we have today is two types of digital imaging.
One is the truly scientific one that uses ALL linear data. The other is
a convenient engineering one that delivers the goods simply, by pre
compensating the linear data to display on non linear displays.

Or, more accuratly, by non-linearly encoding the data in a way that fits
human perceptual abilities without wasting bits.


Engineers were always happy with approximations.

Engineers are happy with what does the job at the lowest cost necessary.
For photometry, you need more bits and a calibrated chain. For
photography you don't.

Dave



Hello

Do they use a high number of bits in space imaging? I cannot imagine
they do as storage must be limited for high amounts of data. After all
the systems in use on say the Cassini mission are over 10 years old in
technology terms. I can see why accuracy is essential for photometry,
but there are also imaging cameras, which should use gamma. I doubt that
these are more than 8 bit per colour.

Mike Engles

As a scientist on the Cassini mission, as well as Mars Global
Surveyor and several past missions, having been a science team member
on multiple planetary and terrestrial missions that defined the science
instruments, I think I can shed some light here. The main thing
to realize is that spacecraft data are first and foremost about
making scientific measurements. Viewing is secondary. All scientific
instruments for which I've been involved with the design (probably
a couple of dozen), the output is digitized directly from the
detectors, whatever form that may be. Since modern electronic detectors
are inherently linear, then the sensor output is digitized linearly.
No instrument that I have been involved with has had some transformation
and all have had lossless compression. In fact early on (say 1980s
into the early 1990s) even mentioning lossy compression in a proposal
was almost certain death to the whole instrument. Today, on the Cassini
spacecraft, my instrument (VIMS: http://wwwvims.lpl.arizona.edu )
does only lossless or no compression at 12-bits/pixel (note, each
pixel has 352 colors, not simply RGB). The camera (ISS), has 12-bit
encoding, but they can do lossy or lossless compression, but I'm
pretty sure (not 100%) that it is linear only. It has a 1024 pixel
square array with 12-micron pixels. I believe I have heard the ISS
scientists say they can do 8-bit encoding as a lossy data compression
(couldn't find that on the web site), but they do not like to use it.
Regardless, once you have good scientific data (which ultimately must be
calibrated to a known scale, like linear in photons per second), you
can transform, and degrade if necessary, the data for viewing.

Roger

"Roger N. Clark (change username to rnclark)" wrote:

As a scientist on the Cassini mission, as well as Mars Global
Surveyor and several past missions, having been a science team member
on multiple planetary and terrestrial missions that defined the science
instruments, I think I can shed some light here. The main thing
to realize is that spacecraft data are first and foremost about
making scientific measurements. Viewing is secondary. All scientific
instruments for which I've been involved with the design (probably
a couple of dozen), the output is digitized directly from the
detectors, whatever form that may be. Since modern electronic detectors
are inherently linear, then the sensor output is digitized linearly.
No instrument that I have been involved with has had some transformation
and all have had lossless compression. In fact early on (say 1980s
into the early 1990s) even mentioning lossy compression in a proposal
was almost certain death to the whole instrument. Today, on the Cassini
spacecraft, my instrument (VIMS: http://wwwvims.lpl.arizona.edu )
does only lossless or no compression at 12-bits/pixel (note, each
pixel has 352 colors, not simply RGB). The camera (ISS), has 12-bit
encoding, but they can do lossy or lossless compression, but I'm
pretty sure (not 100%) that it is linear only. It has a 1024 pixel
square array with 12-micron pixels. I believe I have heard the ISS
scientists say they can do 8-bit encoding as a lossy data compression
(couldn't find that on the web site), but they do not like to use it.
Regardless, once you have good scientific data (which ultimately must be
calibrated to a known scale, like linear in photons per second), you
can transform, and degrade if necessary, the data for viewing.

Roger

Amazon does not carry this camera. Where is it available? Hate to
disappoint those who have it on their lists.

"Roger N. Clark (change username to rnclark)" wrote:

As a scientist on the Cassini mission, as well as Mars Global
Surveyor and several past missions, having been a science team member
on multiple planetary and terrestrial missions that defined the science
instruments, I think I can shed some light here. The main thing
to realize is that spacecraft data are first and foremost about
making scientific measurements. Viewing is secondary. All scientific
instruments for which I've been involved with the design (probably
a couple of dozen), the output is digitized directly from the
detectors, whatever form that may be. Since modern electronic detectors
are inherently linear, then the sensor output is digitized linearly.
No instrument that I have been involved with has had some transformation
and all have had lossless compression. In fact early on (say 1980s
into the early 1990s) even mentioning lossy compression in a proposal
was almost certain death to the whole instrument. Today, on the Cassini
spacecraft, my instrument (VIMS: http://wwwvims.lpl.arizona.edu )
does only lossless or no compression at 12-bits/pixel (note, each
pixel has 352 colors, not simply RGB). The camera (ISS), has 12-bit
encoding, but they can do lossy or lossless compression, but I'm
pretty sure (not 100%) that it is linear only. It has a 1024 pixel
square array with 12-micron pixels. I believe I have heard the ISS
scientists say they can do 8-bit encoding as a lossy data compression
(couldn't find that on the web site), but they do not like to use it.
Regardless, once you have good scientific data (which ultimately must be
calibrated to a known scale, like linear in photons per second), you
can transform, and degrade if necessary, the data for viewing.

Roger

Amazon does not carry this camera. Where is it available? Hate to
disappoint those who have it on their lists.

wrote:

"Roger N. Clark (change username to rnclark)" wrote:


As a scientist on the Cassini mission, as well as Mars Global
Surveyor and several past missions, having been a science team member
on multiple planetary and terrestrial missions that defined the science
instruments, I think I can shed some light here. The main thing
to realize is that spacecraft data are first and foremost about
making scientific measurements. Viewing is secondary. All scientific
instruments for which I've been involved with the design (probably
a couple of dozen), the output is digitized directly from the
detectors, whatever form that may be. Since modern electronic detectors
are inherently linear, then the sensor output is digitized linearly.
No instrument that I have been involved with has had some transformation
and all have had lossless compression. In fact early on (say 1980s
into the early 1990s) even mentioning lossy compression in a proposal
was almost certain death to the whole instrument. Today, on the Cassini
spacecraft, my instrument (VIMS: http://wwwvims.lpl.arizona.edu )
does only lossless or no compression at 12-bits/pixel (note, each
pixel has 352 colors, not simply RGB). The camera (ISS), has 12-bit
encoding, but they can do lossy or lossless compression, but I'm
pretty sure (not 100%) that it is linear only. It has a 1024 pixel
square array with 12-micron pixels. I believe I have heard the ISS
scientists say they can do 8-bit encoding as a lossy data compression
(couldn't find that on the web site), but they do not like to use it.
Regardless, once you have good scientific data (which ultimately must be
calibrated to a known scale, like linear in photons per second), you
can transform, and degrade if necessary, the data for viewing.

Roger


Amazon does not carry this camera. Where is it available? Hate to
disappoint those who have it on their lists.

For ~$35,000,000 you can have one built especially for you.
For a few million extra, you can probably customize it too. ;-)

Roger