Pentax MX-1 vs Pentax Q: read noise comparison

Input-referred read noise at base ISO: Pentax MX-1 4.2 e⁻ (ISO 100), Pentax Q 2.1 e⁻ (ISO 125).

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 Q

The Pentax Q was measured at 18 ISO settings from ISO 125 to ISO 6400. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (125) read noise is 1.04 DN, or 2.1 electrons at the sensor. From ISO 800 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Full well at base ISO is about 8,427 electrons; unity gain is around ISO 260.

Pentax MX-1 vs Pentax Q read noise table

ISO	Pentax MX-1	Pentax Q
100	1.840	–
125	1.828	1.042
160	2.250	1.240
200	2.549	1.434
250	2.969	1.647
320	3.531	1.945
400	4.228	2.362
500	5.169	2.828
640	6.190	3.411
800	7.727	4.112
1000	9.063	5.098
1250	2.621	6.320
1600	3.918	7.835
2000	6.543	9.646
2500	17.148	11.632
3200	23.918	14.420
4000	31.341	18.126
5000	15.562	22.627
6400	24.761	30.065
8000	37.792	–
10000	26.173	–
12800	44.324	–

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