Adobe Photoshop CS2 and ACR Color Settings for Linear space workflow

The linear working-space has been very easy to arrange with Photoshop since the version 5.5, below I explain my CS2 setup.

The linear space profiles are available for download here. They need to be stored to the color profile folder so that they the system and Photoshop will recognize them, this folder is different in different operating systems:

• Windows XP: /Windows/System32/Spool/Drivers/Color
• Windows 2000: /Winnt/System32/Spool/Drivers/Color
• Windows Me and 98: /Windows/System/Color

Firstly I use the AdobeGamma for calibrating and profiling the CRT monitors to gamma 2.5 space. I use the gamma 2.5 calibration chart as the Windows background image to aid the calibration with AdobeGamma.

CS2 Color Settings Dialog

I provide several linear RGB working space profiles they have been developed during the years since 1996. However, for all RGB work I have been using the CIE 1931 D65 profile since the beginning of the year 2004. It provides many benefits from being directly the ICC specification of the CIE 1931 Standard Observer's color space (in RGB mode).

When setting the Photoshop in to the linear RGB workflow the Gray profile must also be set to linear, else there will be conflicts e.g. when using channel channel data. Gray working space can be set by the Linear gray profile (also in the above ZIP archive) or directly from the Gray dropdown by setting it to Custom Gamma = 1.0.

Linear color management setup for Photoshop CS2.

The CMYK and Spot profiles/settings depend solely on the particular printing press in use, I do not use these modes at all.

The Color Management Policies depend on personal preferences and on the chosen workflow practices. I like to preserve ICC profiles instead of having automated conversions be done by Photoshop, this way I feel that I have more firm grip on the color management in my workflow.

I do have an Open Event script that automatically converts the images from Adobe Camera RAW from the ProPhoto profile into the working RGB space ( CIE 1931 D65 Gamma 1) but this is an exception. Generally I do not want automatic conversions to happen, unless of course I'm working with a large batch of images from a known source. Therefore, I have an ActionButton that converts the image to 16-bit/c and to the CIE 1931 D65 Gamma 1 profile, I use that button when I have non-linear images to work with.

Conversion engine has to be kept in Adobe(ACE), since Photoshop is not compatible with the Microsoft ICM engine in conversion between RGB and Gray modes, severe clipping can occur. However, all my Actions and Scripts that convert between two RGB spaces are using the Microsoft ICM engine, this is because the Adobe(ACE) has so called linear slope at the dark end of the tonal range that can very severely damage the very dark image data.

Layer blending in Photoshop is weakly color-managed, Photoshop blends layers arithmetically so the resulting numerical RGB triple is the same no matter in what kind of RGB color space the operation is applied. Arithmetic layer blending operations are the correct methods in the CIE 1931 D65 and CIE 1931 D50 -profiles only. The option 'Blend RGB Colors Using Gamma 1.0' has no effect when the working-space is linear, I just choose to have it set. In non-linear color-spaces the option partially manages the conversion, by converting the RGB data to linear but keeps the particular gamut during the blending operation.

Adobe Camera RAW Settings for Linear space workflow

I have been using the DCRAW converter for my own personal imaging for many years because of the high quality and accuracy it provides. At work I have been using the ACR, because it is very user friendly, fast and easy to use. In general ACR provides very good quality and accuracy also, the only problem it has is that in the very deep dark end it does not give all that image information that the RAW data has and that the DCRAW can provide. But I like the above mentioned qualities of ACR and those cases where I need to seriously pull the most dark image info into visible are very rare. So, in the beginning of the year 2007 I finally decided to switch over to ACR for my personal imaging also. I still keep the DCRAW, but use it only as an emergency tool.

An irritating problem with ACR is that the output is "hardwired" to the four RGB working-spaces in the workflow options. Therefore I take the images in the ProPhoto RGB in 16-bit/c and I wrote an Open event Script that automatically converts those images that are opened to Photoshop by the ACR in to my linear CIE 1931 D65 RGB working-space. This adds about 1.5 seconds to the opening process, so I can easily live with that. But it is irritating anyhow.

ACR provides quite a lot of editing operations and most of them do operate on the linear image data (but in the color-gamut of the camera). However, Photoshop offers much more options and more power for the editing so I prefer to use it for image editing and ACR as the converter.

Therefore in ACR I only use the white-balancing tools (mainly the gray-click method) and the Exposure tool. The white balancing tool behaves nicely colorimetricly and the auto-Exposure is decently accurate, does not clip too much. The auto-Shadow tool sometimes clips too harshly.

So, my ACR is all the time in these kind of settings (and the Open -Event Script brings the image automatically to the linear CIE 1931 D65 Gamma 1 RGB working-space).