TREN
Sony a77 read noise vs ISO
The Sony a77 (SLT-A77V) was measured at 26 ISO settings from ISO 50 to ISO 16000. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.
At base ISO (100) read noise is 3.39 DN, or 4 electrons at the sensor. From ISO 250 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 5000 don't change analog gain (digital push). Full well at base ISO is about 18,921 electrons; unity gain is around ISO 120.
Sony a77 read noise table
| ISO | Read noise (DN) | log₂ |
|---|---|---|
| 50 | ○ 2.949 | 1.56 |
| 64 | ○ 3.411 | 1.77 |
| 80 | ○ 4.000 | 2.00 |
| 100 | 3.387 | 1.76 |
| 125 | 3.918 | 1.97 |
| 160 | 4.757 | 2.25 |
| 200 | 5.657 | 2.50 |
| 250 | 6.774 | 2.76 |
| 320 | 8.225 | 3.04 |
| 400 | 9.918 | 3.31 |
| 500 | 12.210 | 3.61 |
| 640 | 15.032 | 3.91 |
| 800 | 18.507 | 4.21 |
| 1000 | 22.943 | 4.52 |
| 1250 | 29.651 | 4.89 |
| 1600 | 37.271 | 5.22 |
| 2000 | 46.851 | 5.55 |
| 2500 | 58.081 | 5.86 |
| 3200 | 74.028 | 6.21 |
| 4000 | 93.054 | 6.54 |
| 5000 | 115.360 | 6.85 |
| 6400 | ◆ 112.206 | 6.81 |
| 8000 | ◆ 144.007 | 7.17 |
| 10000 | ◆ 181.019 | 7.50 |
| 12800 | ◆ 227.544 | 7.83 |
| 16000 | ◆ 286.026 | 8.16 |