Pentax K20D vs Pentax MX-1: read noise comparison
Pentax K20DDxO
The Pentax K20D was measured at 7 ISO settings from ISO 100 to ISO 6400. Values were derived by Bill Claff from DxOMark lab data.
At base ISO (100) read noise is 2.55 DN. From ISO 3200 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise.
Pentax MX-1
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 K20D vs Pentax MX-1 read noise table
| ISO | Pentax K20D | Pentax MX-1 |
|---|---|---|
| 100 | 2.549 | 1.840 |
| 125 | – | 1.828 |
| 160 | – | 2.250 |
| 200 | 4.993 | 2.549 |
| 250 | – | 2.969 |
| 320 | – | 3.531 |
| 400 | 7.516 | 4.228 |
| 500 | – | 5.169 |
| 640 | – | 6.190 |
| 800 | 11.314 | 7.727 |
| 1000 | – | 9.063 |
| 1250 | – | 2.621 |
| 1600 | 16.223 | 3.918 |
| 2000 | – | 6.543 |
| 2500 | – | 17.148 |
| 3200 | 19.293 | 23.918 |
| 4000 | – | 31.341 |
| 5000 | – | 15.562 |
| 6400 | 37.271 | 24.761 |
| 8000 | – | 37.792 |
| 10000 | – | 26.173 |
| 12800 | – | 44.324 |
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