Same code values? Decode before mixing.

sRGB emerged as a shared interpretation for images crossing devices and applications. The historical Hewlett-Packard/Microsoft proposal sought a practical colour baseline for the internet and desktop systems, particularly when detailed device profiles were absent.

It does not make all monitors identical. It defines the image’s source space; applications and colour management must relate those coordinates to the actual display. “An sRGB file” and “a calibrated screen” are different statements.

sRGB uses R (0.640, 0.330), G (0.300, 0.600), B (0.150, 0.060), D65 white and a piecewise transfer function. Coordinates belong to a defined colour representation, not merely three slider positions.

Code [0.5, 0.5, 0.5] is neutral relative to this white, but it is not half of linear light. Decoding yields approximately 0.214 per channel. Do not confuse this relative value with physical screen luminance in cd/m².

Shared Rec.709 primaries imply the same linear RGB matrix when white normalization also matches. They do not remove differences in encoding and display assumptions.

A graphic and video may need no gamut-basis conversion, yet still need tone-interpretation handling. Establish whether you are preserving finished artwork’s appearance or performing another explicitly defined operation. Simply replacing one tag with another does not specify that intent.

Decode C using C/12.92 when C ≤ 0.04045; otherwise use ((C + 0.055)/1.055)^2.4. The inverse uses a 0.0031308 breakpoint. These branches explain why sRGB is neither exactly gamma 2.2 nor a pure 2.4 power.

Light calculations operate after decoding. A half-and-half linear-light black/white mixture encodes to roughly 0.735, whereas averaging codes gives 0.5. Both are defined operations with different purposes; linear mixing does not promise perceptual uniformity.

The ICC registry relates sRGB to a reference display context, including D65 and reference white at 80 cd/m². This is a descriptive model, not a statement that your browser window physically emits that luminance.

Device brightness, display profile, application colour management and surround remain separate factors. Correct coordinate conversion alone cannot guarantee the same subjective appearance in a bright room and a darkened studio.

A profile relates file values to a defined colour meaning. Assigning a profile describes existing numbers; converting to a profile recalculates coordinates under a chosen transform. These are different actions.

Do not assign Display P3 to a correctly tagged sRGB image just to intensify colours: that reinterprets the numbers. Missing profiles require investigating the source, not choosing the prettiest result. An application’s sRGB default is an assumption, not source evidence.

Ordinary CSS HEX, rgb() and hsl() specify sRGB colours. #ff0000 is not the most saturated red the current display can produce. Another space needs an explicit notation such as color(display-p3 …).

CSS Color 4 separately describes spaces, interpolation and out-of-gamut handling. A checked draft specification is not a guarantee that a particular browser implements every feature. Test the required functions and the readability of fallbacks.

Wide-gamut web presentation requires a coherent chain: a correct colour definition, application support, colour management and a capable display. A P3 tag alone cannot extend hardware capabilities.

The swatches in this chapter’s labs deliberately use sRGB. That makes the preview path explicit. Evaluating actual wide-gamut output needs an appropriate display path; numerical conversions should still be checked separately from visual impressions.

Artwork, photographs and clips may arrive in different source representations. A finished sRGB PNG does not become camera log merely because it enters a DWG/Intermediate timeline. Transparent files also require separate alpha and edge checks.

Agree the source space, desired appearance preservation and working domain. If darkening appears only after compositing, inspect blending and alpha interpretation as well: the profile is not necessarily the source of the error.

With matching primaries and D65, no linear RGB basis change is necessary. Yet a finished display image and a pre-rendering signal have different meanings even when both are called RGB.

Converting sRGB artwork for video begins by decoding it, then performs the necessary reconciliation and output encoding. The exact process depends on intent: preserve a finished appearance, integrate an image into a scene, or prepare another master. Do not stack every available transform indiscriminately.

Before delivery, verify source provenance, profile assignment, working space and destination. For web imagery, check the profile and managed browser view; for video, also check levels, codec and colour tags.

Preserve embedded profiles where the workflow expects them. File size, resolution and profile presence alone do not prove colour correctness. Keep a control frame and a short test to detect changes during re-export or transfer to another application.