#2 raster bit depth - 2

Jim Julian

Recently, a new technology has been emerging from
the film industry and is showing up in computer graphics
rendering software, image browsers and editors. The
technology is referred to as HDR or HDRI (High Dynamic
Range (Imaging) ). The purpose of the technology is
to capture as wide a dynamic range of information as
possible. A good analog would be sound technology and
the decibel log scale. Typically, a digital image contains
but a small fraction of the information available in raw data
from digital cameras ( handhelds, satellite, etc.). The HDR
approach uses floating point file formats for storage of
a broader range of data than existing digital formats
can hold. A series of f-stops can be recorded in one file,
providing access to more data and allowing construction
of more accurate images.
Among the formats used are a portable bitmap
version known as a Portable Float Map, a TIFF with
a floating point format, a LogLUV format related to SGIs
proprietary HDR format. Jan 7, ILM released their EXR
HDR format as opensource (ILM - Industrial Light and
Magic, Stevern Spielburg). Several applications have been
developed that are based on HDR technology. HDRShop
( Paul Debevec - http://www.debevec.org ) and Radiance/
Desktop Radiance are the most notable (radsite.lbl.gov/
radiance/HOME.html and http://radsite.lbl.gov/deskrad ).
Reindeer Graphics has produced an HDR plugin for
Photoshop. Among the renderers with HDRI support
are 3D Studio Max, Brazil, Blender, Povray, and others.
For comprehensive information on the technology, I refer
you to Paul Debevec's site at http://www.debevec.org ,
where information on file formats, sample images, links
and software (HDRShop) are available.

I think at some point in the future, adding HDR support
to OpenEV will enhance the programs remote sensing
capabilities and provide the GIS community with a tool
that, in addition to being versatile as well as extremely
useful, is very advanced and "state of the art".

Thank you for your time and attention
Jim Julian


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