Pixel SNR vs Illuminance
Plot signal-to-noise ratio as a function of photon count (illuminance). Visualize noise breakdown by source and compare actual sensor performance against the ideal shot-noise limit.
SNR vs Illuminance
Analyze SNR across signal levels with noise breakdown. Compare different pixel configurations and identify noise-limited regions.
SNRmax
40.0 dB
Unity SNR
6 photons
20dB Threshold
156 photons
Saturation
14286 photons
SNR Model
SNR = N / sqrt(σ_read² + N + (PRNU × N)²)
Where:
- N — signal electrons (photon count × QE)
- σ_read — read noise (electrons RMS)
- PRNU — photo response non-uniformity factor
Noise Regions
| Region | Dominant Noise | SNR Slope |
|---|---|---|
| Low light | Read noise | SNR ∝ N |
| Mid range | Shot noise | SNR ∝ √N |
| High signal | PRNU | SNR saturates |
Key Markers
- Unity SNR (0 dB) — signal equals noise, minimum useful exposure
- 20 dB threshold — often considered minimum for acceptable image quality
- Saturation — full well capacity reached
TIP
The gap between actual and ideal (shot-noise-limited) SNR curves reveals how much the sensor electronics degrade performance. A narrower gap indicates better sensor design.