New article on color management

Started Apr 26, 2013 | Discussions thread
Detail Man
Detail Man Forum Pro • Posts: 16,678
Re: Hope this may help a bit ...

gollywop wrote:

Hugowolf wrote:

gollywop wrote:

And, although the spaces are based on integer values, processing is done with floating point numbers.

In processors like RPP, Rawtheraee, and PhotoNinja, yes.  In ACR/PS, I don't think so.  Adobe still uses integer arithmetic as far as I know.  But I'd certainly be willing to be guided to documentation that says otherwise.

I would be surprised if it were otherwise. It is standard practice to map 0-255 to 0-1, it is just much easier to algorithmically process that way.

Surprise is indeed fun. But I'm waiting for documentation that supports the surprise.

Meanwhile normalizations do not require floating point.

Regarding the 2010 processing, Ken is a quite knowledgeable chap:

kenw wrote:

I'm really curious to watch what RT and RPP start to be able to do with floating point processing and cameras like the K5 which have incredibly low read noise compared to something like ACR/LR that uses fixed point algorithms optimized for speed.

Regarding the 2012 processing, certain floating-point functionality (to some extent) exists:

... Lr 4.1 and ACR 7.1 have the ability to import and render floating-point HDR images.  Supported formats are TIFF and DNG.  (If you have HDR images in other formats like OpenEXR or Radiance, you can use Photoshop or other tools to convert them to TIFF.)  Supported bit depths are 16, 24, and 32 bits per channel.

If you're using Photoshop's Merge to HDR Pro feature to perform the "merge" step, be sure to choose 32-bit output in the top-right popup menu of the HDR Pro dialog box.  This will generate a floating point (but not yet tone-mapped) image, which you can then use ACR or LR to render and tone map using the new PV 2012 controls.

-Eric Chan, Reply #2 on: May 31, 2012, 09:44:14 AM

Apparently, when Eric and the other engineers work working on the V4 PV2012 develop module sliders, they used 32 Bit floating point HDR images to make sure there was sufficient slider capabilities. Then the finalized the basic module. After releasing V4 they realized the power was there for handling HDR 32 bit floating point files so they incorporated it into V4.1.

-dmward, 23rd of September 2012, Post 15

Eric Chan has informed me that there are two image-processing pipelines in Lightroom: output-referred, and scene-referred. Raw files get the scene-referred pipeline. Integer TIFFs get the output-referred pipeline. Therefore, the TIFF test images are getting a different set of processing than LR applies to raw files.

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