Yeahhhh... but this one goes to 11.
A.
> -----Original Message-----
> From: owner-xsi(at)Softimage.COM
> [mailto:owner-xsi(at)Softimage.COM] On Behalf Of Luc-Eric Rousseau
> Sent: 11 July 2007 19:45
> To: XSI(at)Softimage.COM
> Subject: RE: Slider values and bit depth
>
> Parameters like the color in the render tree are not anything
> absolute, they are simply weights used in a formula, which is
> already operating in linear space and how you use it doesn't
> change depending on the bit depth. They're mathematical
> factors. Color is not absolute but relative to what's already
> there and how it will be mapped to display.
>
> For Photoshop where you're not only transforming pixels
> relatively but setting new values, the user is picking color
> based on what it will look like for printing and display, and
> therefore there is no change with the bit depth storage.
>
> For an app where you would paint the 'raw' color value in a
> floating point buffer, no one can tell you what is the
> 'possible range', it
> depends how you will use the data to a device later. Linear floating
> point space only means that for a given color value, a value
> twice its amount is twice as bright. There is no maximum or
> minimum, it only defines how values are to be interpreted
> relatively to each other.
>
> OpenEXR anchors by default the color of a photographed 18%
> gray card to the floating-point value 0.18, and you'd be
> painting values relative to that, hopefully with a look up
> table so you can tell what it'll look like, unless you're
> only doing relative changes. There is no white point at this
> stage because white points are defined as the maximum limit
> of the display medium, it's arbitrary.
>
> HLS/HSV ranges never changes. It defines a convenient cone
> of color for humans on 8-bit interface display, in monitor
> gamma, with 0.0 being black and 1.0 being the white point of
> the monitor. It predates any
> concept of color management. It's possible in some apps to poke HSV
> values outside of 0.0 and 1.0 range, but these values have no
> absolute meaning without the rest of the color management
> pipeline, HLS/HSV is not defined when out-of-range.
>
> The raw linear floating point data needs to be exposed and
> mapped to a display before it has meaning, like taking a
> picture. When you expose it, the raw floating point data is
> in fact used as a mathematical factor in a formula, again.
>
> If you don't use any look-up-table to view floating point
> data, then you are not in fact working in linear space and
> all the color controls work the same was a they do in 8-bit,
> with 1.0 meaning the white point of the monitor.
>
>
>
> > From: Christian Rittener
> >
> > Damn. Nobody cares. Or nobody knows.
> >
> >
> > > -----Original Message-----
> > > From: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] On
> > Behalf
> > > Of Christian Rittener
> > > Sent: July 9, 2007 11:08
> > > To: XSI list
> > > Subject: Slider values and bit depth
> > >
> > > The other thread about bit depth gives me the opportunity
> to finally
> ask
> > > this: when working with 32-bit linear float images, what's the
> > > possible range of normalized-for-8bits values for RGB sliders in
> > > your standard graphics app (Photoshop, Fusion, XSI, ...) ? what
> about HLS values?
> > > Does
> > > this range apply to lights in XSI as well?
> > >
> > > Christian Rittener
>
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