TREN
Pentax MX-1 read noise vs ISO
The Pentax MX-1 was measured at 22 ISO settings from ISO 100 to ISO 12800. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.
At base ISO (100) read noise is 1.84 DN, or 4.2 electrons at the sensor. From ISO 400 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 1000 don't change analog gain (digital push). Full well at base ISO is about 8,824 electrons; unity gain is around ISO 230.
Pentax MX-1 read noise table
| ISO | Read noise (DN) | log₂ |
|---|---|---|
| 100 | 1.840 | 0.88 |
| 125 | 1.828 | 0.87 |
| 160 | 2.250 | 1.17 |
| 200 | 2.549 | 1.35 |
| 250 | 2.969 | 1.57 |
| 320 | 3.531 | 1.82 |
| 400 | 4.228 | 2.08 |
| 500 | 5.169 | 2.37 |
| 640 | 6.190 | 2.63 |
| 800 | 7.727 | 2.95 |
| 1000 | 9.063 | 3.18 |
| 1250 | ▼ 2.621 | 1.39 |
| 1600 | ▼ 3.918 | 1.97 |
| 2000 | ▼ 6.543 | 2.71 |
| 2500 | ▼ 17.148 | 4.10 |
| 3200 | ▼ 23.918 | 4.58 |
| 4000 | ▼ 31.341 | 4.97 |
| 5000 | ▼ 15.562 | 3.96 |
| 6400 | ▼ 24.761 | 4.63 |
| 8000 | ▼ 37.792 | 5.24 |
| 10000 | ▼ 26.173 | 4.71 |
| 12800 | ▼ 44.324 | 5.47 |