If you're using HDR, you can't enable the Image Clip effects. The image clip effects are all low-dynamic range and will clip the HDR values. Why would you want to use the 8-bit to 16-bit conversion? An HDR file is floating point not 8-bit.
That bit depth conversion effect is used in theory when you want to use an 8-bit image for a displacement map, and you convert it to 16-bit before using correction or blur on it, to get extra detail. This is all in the manual.
The display gamma stuff is all for viewing the images correctly in OpenGL, and it's already offering the correct parameters and correct features. You do not use any gamma correction before sending the image to Mental Ray, but let mental ray load the image directly without any preprocessing, and do any processing in the render tree instead. The Image Clip has gamma correction for OpenGL, and the render region has its display gamma setting too. This is all explained on the wiki.
"Display Gamma Affects Rendering" is mostly for users who don't understand linear floating point, or dont' want to use it (because it can indeed be a pain). It's gamma correction implemented in the mental ray image shader itself, as if you had added a gamma node in the render tree
------------------
Luc-Eric Rousseau
Team Leader, User Interface
Softimage|XSI
> -----Original Message-----
> From:Tim Leydecker
>
> Hi folks,
>
> I have problems in understanding the behaviour
> and settings when using an environment shader
> together with a *.hdr file in XSI 5.01 (5.1different?).
>
> *Will the high dynamic range be used by default?
>
> *Why does the intensity change (in a rendering) when
> you click "Adjust>enable effects", shouldn´t the intensity
> stay as it is until you actually modify an accompanied slider?
>
> *Is the conversion from 8>16 bit to be checked or not?
>
> *How do I block the environment shader from appearing
> in the alpha channel?
>
> *I simply don´t get the behaviour of the "Display Gamma"
> and "Display Gamma affects rendering" depending on wether
> "Enable Effects" is a ctive or not.
>
> I *think* one would want to have linear input for
> rendering and only the final result gamma corrected?
> Or do I need to have gammacorrected input to get
> reliable gammacorrect output without wasting details?
>
> *8-16 Bit per channel just interpolated values to fake
> a higher dynamic range, doubling them or what does it?
>
> What I´d like to have:
>
> *Display Gamma for previewing the image according to the
> monitor settings (e.g. 1 - 2,2). As you´ll probably know it
> from hdrshop...
>
> *Exposure (f-stops) moved to the "enable effects" section.
> *ColorCorrection not modifying anything unless you change
> a sliderposition
>
> *"DisplayGamma affects rendering" renamed to something
> that makes you understand the Gammacurve of the image
> is either modified (>monitor) or maybe even ignored for
> linear...
>
> *Add an Alpha (>blackhole)switch to the Intensity sliders
>
> *Move the Intensity sliders to the "Adjust" page.
>
>
> Cheers
>
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