SUMMARY
Dual gain ISO, also known by various similar terms, refers to camera sensors that utilize a second readout mode with a different amplification configuration. This technology allows sensors to offer better shadow performance at higher ISOs than traditional single-gain designs. The sensor's pixels have a switchable capacitor that engages at low ISOs for high dynamic range and disengages at a specific threshold, boosting conversion gain to reduce the impact of read noise. Understanding this gain structure can change how photographers approach exposure, moving beyond treating ISO as a simple brightness control.
TAKEAWAYS
ISO controls signal amplification after light capture, not sensor sensitivity.
Dual gain sensors have a second readout mode that improves shadow performance at higher ISOs.
The 'switch point' where dual gain activates varies by camera model and sensor design.
Understanding dual gain helps photographers use ISO more effectively as a technical and creative tool.