An average of display code values need not equal the encoded result of averaging their corresponding linear-light values.
Keep the averaging domain
An sRGB encoded component and its linear-light counterpart are related by a transfer function. Averaging encoded values and averaging decoded linear-light values are different calculations. The selected domain therefore belongs to the operation definition before a resulting gray level is compared or interpreted. Primary reference: W3C sRGB encoded and linear-light transfer functions.
For an original worksheet, retain the component encoding and the conversion direction. Do not describe a storage-range normalization as the same operation as transfer-function decoding. Both can produce fractional numbers while assigning them different numerical meanings.
Compare fictional black and white
Use encoded endpoints 0 and 1 in a teaching sRGB component. Their encoded arithmetic mean is 0.5. Their linear-light endpoints are also 0 and 1; averaging those gives linear 0.5, which encodes to approximately 0.73536 under the stated sRGB transfer function.
Conversely, encoded 0.5 decodes to approximately 0.21404 linear. The difference follows the nonlinear mapping, not a changed pair of original endpoints. This original arithmetic is not a measurement of physical display brightness, camera exposure or an approved printing color.
Retain the conversion sequence
Prepare an original record with input codes, decoded components, chosen averaging domain and final encoding. Compare outputs only after confirming which sequence each used. If a processing route changes the domain, preserve that change explicitly instead of treating its new gray value as unexplained inconsistency.
The guide prescribes no HM image-processing domain or color tolerance. Its reader decision is whether the averaging quantity was defined. Color-profile management, device response and task-specific evidence are separate requirements when the number supports an actual visual comparison.
Customer Questions
What is the mean of the fictional encoded endpoints?
Zero point five.
What is encoded linear-half under the stated transfer?
Approximately zero point seven-three-five-three-six.
Is normalizing the storage range the same as decoding the transfer?
No. They assign different numerical meanings.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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