TREN
Sony a68 read noise vs ISO
The Sony a68 (ILCA-68) was measured at 25 ISO settings from ISO 100 to ISO 25600. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.
At base ISO (100) read noise is 2.58 DN, or 3.9 electrons at the sensor. From ISO 640 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 10000 don't change analog gain (digital push). Full well at base ISO is about 23,773 electrons; unity gain is around ISO 150.
Sony a68 read noise table
| ISO | Read noise (DN) | log₂ |
|---|---|---|
| 100 | 2.585 | 1.37 |
| 125 | 2.908 | 1.54 |
| 160 | 3.458 | 1.79 |
| 200 | 4.000 | 2.00 |
| 250 | 4.691 | 2.23 |
| 320 | 5.657 | 2.50 |
| 400 | 6.774 | 2.76 |
| 500 | 8.056 | 3.01 |
| 640 | 9.849 | 3.30 |
| 800 | 11.876 | 3.57 |
| 1000 | 14.320 | 3.84 |
| 1250 | 17.877 | 4.16 |
| 1600 | 21.407 | 4.42 |
| 2000 | 26.909 | 4.75 |
| 2500 | 34.297 | 5.10 |
| 3200 | 43.111 | 5.43 |
| 4000 | 52.346 | 5.71 |
| 5000 | 67.182 | 6.07 |
| 6400 | 85.036 | 6.41 |
| 8000 | 105.420 | 6.72 |
| 10000 | 134.364 | 7.07 |
| 12800 | ▼ 131.599 | 7.04 |
| 16000 | ▼ 168.897 | 7.40 |
| 20000 | ▼ 210.839 | 7.72 |
| 25600 | ▼ 257.781 | 8.01 |