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sRGB profiles

Introducing the sRGB_v4_ICC_preference.icc profile

The sRGB v4 ICC preference profile is a v4 replacement for commonly used v2 sRGB profiles. It gives better results in workflows that implement the ICC v4 specification. It is intended to be used in combination with other ICC v4 profiles.

The advantages of the new profile are:

  1. More pleasing results for most images when combined with any correctly-constructed v4 output profile using the perceptual rendering intent.
  2. More consistently correct results among different CMMs using the ICC-absolute colorimetric rendering intent.
  3. Higher color accuracy using the media-relative colorimetric intent.
A typical use case would be to print sRGB images captured with a digital still camera. In this case a user could open the image in Adobe® Photoshop®, assign the sRGB v4 profile as shown in Figure 1. Adobe® Photoshop® is either a registered trademark or trademark of Adobe Systems Incorporated in the United States and/or other countries.

Figure 1. Assigning the sRGB v4 ICC preference profile. Adobe product screen shot reprinted with permission from Adobe Systems Incorporated.

The user would then convert the data to printer specific values with the sRGB v4 profile as source, the v4 printer profile as destination, and selecting the perceptual rendering intent, as shown in Fig 2.

Figure 2. Conversion from sRGB v4 ICC preference profile to v4 printer profile in Photoshop using the perceptual rendering intent. Adobe product screen shot reprinted with permission from Adobe Systems Incorporated.

The three available rendering intents of the sRGB v4 profile should normally be used as follows:

  • The ICC-absolute colorimetric rendering intent should be used when the goal is to maintain the colors of the original on the reproduction,
  • The media-relative colorimetric intent should be used when the goal is to map the source medium white to the destination medium,
  • The perceptual intent should be used when the goal is to re-optimize the source colors for the reproduction medium while maintaining the "look" of the source image
The re-optimization performed by the perceptual rendering intent of the profile is a result of using the Perceptual Medium Reference Gamut defined in the ICC v4 specification as an intermediate rendering target. No perceptual reference medium is defined for v2 profiles.

Advice for caution

Ideally the ICC v4 profile should not be combined with ICC v2 profiles. If that is unavoidable, see the intermediate-level ICC White Paper 26 'Using the sRGB_v4_ICC_preference.icc profile' for additional information and recommendations.

The sRGB v4 profile will in some cases not produce the same results as would be obtained using an sRGB v2 profile. Differences will depend on the particular sRGB v2 profile and rendering intent used. See the intermediate level white paper for additional information and recommendations.

Summary Overall users can expect to get better and more consistent results using the sRGB v4 profile versus the sRGB v2 profiles. More details are available in White Paper 26.

sRGB_v4_ICC_preference.icc    
 
This sRGB_v4_ICC_preference.icc profile is a Beta version. Feedback on the performance of the profile (whether positive or negative) would be greatly welcomed. Please send comments to ICC users (Subscribe to ICC users mailing list here.)

v2 profiles

Two ICC version 2 (v2) sRGB profiles are provided below, one with XYZ black point scaling to zero, and one without. The 'black scaled' profile has the preferred rendering intent in the header set to 'perceptual'. and the 'no black scaling' profile has the preferred rendering intent in the header set to 'relative colorimetric'.

Both profiles contain the standard linearized Bradford D65 to D50 chromatic adaptation tag (this tag was often not present in older sRGB profiles), and the media white point tag is set to D50 (as is required for ICC v4 profiles). This avoids the inappropriate color casts that older sRGB v2 ICC profiles sometimes produced when the absolute colorimetric intent was used.

The 'black scaled' profile will work correctly when either Black Point Compensation (BPC) is on in the CMM/application, or the other profile transform to be used for the conversion is also black scaled. Black scaled profiles are needed when BPC is desired for the conversion but the CMM to be used does not support BPC. Most v2 sRGB profiles in current use are black scaled because they are intended to be used as the source profile in conversions where the destination profile perceptual intent will be used (v2 perceptual transforms typically include black scaling).

The 'no black scaling' profile produces sRGB colorimetry in the PCS that is more accurate to what a viewer of a sRGB calibrated display will observe in the reference sRGB viewing conditions. This is the case when the display has been calibrated to include the viewer-observed black level such as one might achieve with a non-contact monitor calibrator or other means to include ambient effects. It should be used in situations where greater colorimetric accuracy is desired, e.g. as the destination profile for preview on calibrated sRGB displays where the viewer-observed black has been included. However it should be noted that most current LCD displays, even those that use the sRGB primaries and gamma, have a higher white point luminance and dynamic range than the sRGB reference display. To produce accurate preview colorimetry on these displays they should be accurately profiled, instead of using an sRGB profile.

The 'no black scaling' profile can be used with BPC on or off in the CMM. If it is used with BPC on the results should be the same as when using the 'black scaled' profile. If it is used with BPC off it will produce un-black-scaled media-relative colorimetry: if the source encoding has tones darker than the destination encoding black point they will be clipped, and if the source black point is higher than the destination black point the source black point will be accurately reproduced.

Note that these profiles were previously named 'sRGB_IEC61966-2-1_noBPC.icc' 'sRGB_IEC61966-2-1_withBPC.icc' to indicate whether black scaling had been applied in the profile. They have been renamed to reduce ambiguity over their use with black point compensation.

Terms of use

To anyone who acknowledges that the files "sRGB_IEC61966-2-1_no_black_scaling.icc" and "sRGB_IEC61966-2-1_black scaled.icc" are provided "AS IS" WITH NO EXPRESS OR IMPLIED WARRANTY, permission to use, copy and distribute these file for any purpose is hereby granted without fee, provided that the files are not changed including the ICC copyright notice tag, and that the name of ICC shall not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. ICC makes no representations about the suitability of this software for any purpose.

 

sRGB_IEC61966-2-1_no black_scaling.icc    
 
sRGB_IEC61966-2-1_black_scaled.icc