 Transmission electron microscopy contrast

Transmission electron microscopy contrast is a difference in recorded signal between specimen regions under specified illumination, angular acceptance and detector settings. For a positive reference signal $S_{\mathrm{ref}}$, one possible signed contrast convention isNegative $C$ means darker than the reference; it does not specify a surface height or chemical composition. The definition must accompany a numerical contrast value, since other conventions exist. A conspicuous feature need not establish fine spatial resolution: detecting a small signal difference and distinguishing two nearby features are different measurement questions.