What SideScopes measures

Where the measurement occurs

SideScopes sits after the source application has rendered its interface and image for the desktop. The operating system supplies pixels for the selected screen region, and SideScopes derives every trace and readout from those pixels.

This application-independent position is useful: the same instruments can observe a browser, image editor, video application, compositor, reference viewer, or any other visible content. It also defines what the result can and cannot mean.

source media or document
        ↓
application processing and color management
        ↓
desktop composition / screen-capture result  ←  SideScopes measures here
        ↓
display pipeline and physical screen

SideScopes cannot look backward through that chain. It does not know the source bit depth, RAW latitude, timeline working space, node graph, document profile, mastering metadata, or whether a value was limited at an earlier stage. It also does not measure the final display’s emitted light.

Capture precision and dynamic range

On macOS, SideScopes requests packed 10-bit RGB frames from ScreenCaptureKit. When the system supplies that format, the scope engines read its 0–1023 channel codes directly rather than first reducing them to eight bits. This can retain finer screen-rendered steps in smooth gradients when the source application and desktop compositor provide them. It cannot restore precision that is absent from the rendered image, and textured or noisy content may show little practical difference.

The requested format is not assumed: SideScopes checks every delivered frame and also accepts the eight-bit fallback. Windows capture currently uses eight-bit BGRA frames.

Bit depth and dynamic range are separate properties. Ten-bit capture does not give SideScopes access to source-media values or HDR headroom. HDR and EDR content is measured through the SDR rendition available to screen capture; highlights above SDR white may therefore appear clipped even when the source still contains detail. SideScopes is not an HDR signal-analysis tool.

Color assumptions

The desktop capture is requested or labeled as sRGB where the operating-system API permits. SideScopes then interprets the received RGB values as full-range, sRGB-like display data:

• Vectorscope uses a fixed Rec.709-style R′G′B′-to-chroma matrix;
• Luma Waveform uses Rec.709-style encoded Y′ coefficients;
• Color Picker’s CIELAB and CIEDE2000 readouts assume sRGB primaries, the sRGB transfer function, and a D65 white point.

sRGB and Rec.709 share primary chromaticities and a D65 white point, but they are not complete synonyms: their encoding conventions and intended viewing systems differ. SideScopes’ plots are practical display-referred instruments, not a declaration that every captured application is operating in Rec.709.

What is not color-managed

SideScopes does not inspect or apply:

• the source document or media profile;
• the source application’s working or timeline color space;
• the display ICC profile or calibration state;
• an output, printer, or paper profile;
• HDR mastering metadata or an absolute-nit transfer function.

It is therefore not a soft-proofing system, gamut checker, signal-compliance monitor, colorimeter, or spectrophotometer. Vectorscope target boxes are color-bar references, not gamut boundaries. Values from two displays or two different desktop pipelines are not automatically comparable even when the same nominal RGB triplet appears.

Reliable uses

SideScopes is strongest when the measurement path is held constant and the question concerns the visible result. Examples include:

• observing how a source-application adjustment changes its rendered output;
• locating channel or level relationships within a selected region;
• comparing corresponding areas in two images on the same system;
• checking continuity while keeping display and application conditions fixed;
• studying how the scopes encode the same pixels in different ways.

When delivery compliance or upstream signal values matter, use scopes inside the application that owns that signal, configured for the relevant color space and range. When physical display or print accuracy matters, use a calibrated measurement device and the appropriate color-managed workflow.

The limitation is not hidden uncertainty around an otherwise source-level measurement; it is the explicit boundary of a screen-capture instrument.

Technical references

• ITU-R BT.709 defines the Rec.709 system used as the coefficient reference.
• The International Color Consortium’s registry entries for BT.709 and sRGB list their shared primary chromaticities and their distinct transfer and viewing specifications.