Re: 8 verses 16 bit

[David Chien <chiendh@xxxxxxx>]

> >As a result, using a 8-bit color system immediately prevents you from
> >recording subtle color shading in certain types of photography - eg.
> >flowers, skin tones, etc.
> >
> That is true - it prevents you from recording them, but not from SEEING
> them - your own visual system imposes that limitation.  In order to see
> them and differentiate them one from another you need to modify the

  Here my interest is not only is seeing differences, but recording the
full range in case manipulations are to be done on the images later.

  eg. to prevent color banding during image manipulation.
  eg. to prevent inaccurate results during scientific and medical
diagnosis and imaging.
  eg. to allow full recording of 10+ bit gray scale images used in such
fields.
  eg. to allow machine analysis and program assisted manipulation and
evaluation of images.

  We already know that the color reproduction gamut of print and
monitors is far smaller (that triangle you see within the CIE color
space) than the entire range of colors the human eye can see.  Even so,
developments continue to push the boundaries of imaging technology far
beyond what humans can reproduce in their machines, or yes, even see -
depending at times upon the machines they've created to help them along.

> the range of colours that the eye can discern.  Further processing of
> either of these parameters by necessity introduces visible
> discontinuities.  However, when set correctly in the first place, 8 bits
> is more than up to the job of image reproduction.

  Again, if it were, movie companies would never bother with scanning in
their films at more than 8-bits.  Yet, they've found that even with
their expensive scanners, and experienced operators, there is a
difference that matters, and they've happily converted to higher-bit
systems.

  It's not to say that 8-bits is not adaquate for the majority of users
- which I've stated before.  It's the picky ones worried about whether
that's a tumor or not, whether that's a star or nova, whether color
banding will occur or not, etc. that worry about such high-bit systems.

  For most people, 8-bit scanners are just plain peachy.

> >So how many more colors are enough?
> >
> >One simply looks to various sources - film scanners, 3D raytraycing used
> >in movies, human vision studies, 35mm film, etc. and you'll see a varying
> >range being used, all greater than 8-bits because it has long been known
> >to be inadaquate.
> >
> >16-64 bits are all in use
> 
> Name one scanner which uses 64bits per colour!  For that matter, name
> one that uses more than 16 bits at the ADC!

  Ahem, excuse the loss of brain cells here.  
  32-64 bits total or 10-16 bits per channel systems are in use today.

> >, and I myself would prefer at least a 32-bit
> >color system to stay in sync with higher-bit applications in other

> That is losing the plot David.  The Geoforce cards output 8-bit colour
> in all of their modes - 16 million colours.  8 bits in each colour
> represents 24 bits total. The remaining 8 bits are used for texture
> overlays, lighting, antialiasing and 3-D geometry effects and

  Various reasons as a programmer or developer:
  1) 32-bit including alpha channel - thus 24-bit + 8 bit alpha
  2) 32-bit total to match 32-bit color modes in various video cards w/o
converting up from 24-bit images.
  3) aligned along 8-bit byte boundaries and 16/32-bit pipeline paths of
the CPU.
  4) more the merrier ;)
  5) in par with the lower end of high-bit color processing systems, eg.
used in film industry (although they go up to 64-bits total).

  Whether video cards lie when they say they're in 32-bit mode is an
issue for the lawyers...

> >While this still occurs in a 16+bit system, the visual artifacts such as
> >banding are far, far less noticable, if at all.  More bits simply lets you
> >calculate things far more accurately.
> >
> This is NOT giving you more colours to see - it is manipulating the data
> that you have captured INTO the range of colours that you can see: a
> range which is completely encompassed by 8-bit representation of the
> primary colours under an appropriate gamma curve.

  Er?   If I can see a shade of whatever color and another shade of
whatever color and a shade in between, but a 8-bit system can't display
that in-between color because it doesn't have enough bits, I can't see
it.

  Yes, the range of colors (max to min) is still the same, 0-255 in a
8-bit system, but the colors in between, eg. 240.5 between 240 and 241,
are missing.

  If that just happens to be a color shade you can see, but the 8-bit
system can't display, that's another matter....

  Also, within the current settings of that 8-bit system, dithering
occurs because it doesn't have that intermediate color.  That you can
see as color banding, so there is something missing.

> So why do you want 32 bits per colour if no instrument used in the
> photographic reproduction process can utilise it?  Even those you have
> >Aside from the commerical uses, the medical industry would also benefit
> >from photo editors that use 16-64bit image modes.
> Come on David, you can do better than tug at the old bleating
> heartstrings - that is just plain BS: and you KNOW it!

  Er?  Grayscale 10-16bit MRI, CT, and Ultrasound images already are in
use and existance today, well outside the 8-bit gray limit of and 8-bit
system.

  Pulling hearstrings, yes!  

  But not in use?  Medical, scientific and movie industries have already
moved on.  Even digital cameras and scanners produce more bits than will
fit in a 8-bit system.
  I'd say it's only a matter of time before consumers move on.

  These latter consumer points don't care about whether you can 'see'
the different shades, only that you can capture - hopefully, viewing
technology will similarly improve as time progresses.

> Whilst there IS an argument for Photoshop evolving to n-bits per channel
> for all operations (the counter argument of insisting that certain
> operations are implemented in a specific order - maintaining full source
> dynamic range until output eliminates such restrictions) it is certainly
> difficult to argue that n should be greater than 16 - and the argument
> that you have presented is so full of inconsistencies that it does

  While more than 16-bits may not be 'necessary' today for the majority,
and perhaps minority of users, I did say that rather than fix the number
of bits Photoshop works in, it is best to make it completely flexible,
something the user can decide.  And it's only time before imaging
technology catches up and exceeds 16-bits, so why force users into x
bits mode?

  Then, the user simply picks however many bits he desires to work in
(8, 16, 24, 32, etc).  All of the filters and plugings would simply be
rewritten to work their calculations on whatever bit system image is fed
to them, and spit out an apporpriate answer. That is not too hard by any
means to do - eg. see Mathmatica which has done for years, variable
decimal point output in calculations.

  -----

  Imaging encompasses more than simply what-you-can-see-on-screen, but
also what you can detect and calculate from the images you capture.  If
you must change display gamma and settings to see a particular range of
shades of note within an image doesn't preclude it's importance, nor the
usefullness of capturing that many bits.

  Again, most of this talk is pointless for most users who can be happy
in 8-bit mode.  For the techs, medical, scientific, research, and other
users, more is prefered and needed today.

  As for is it enough?  You never know until you've tried.  Many people
thought maybe 128-bits was more than sufficient for encryption, but
today, even 1024-bits seems inadaquate given the rapid development of
processors, and budding quantum computing technologies.  While x-bits
isn't an issue for most users, for those wanting to achieve this or that
result, it may well be needed.
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