Pentax K-5 II s vs Pentax K-50: read noise comparison

Input-referred read noise at base ISO: Pentax K-5 II s 3.3 e⁻ (ISO 80), Pentax K-50 7.2 e⁻ (ISO 100).

Pentax K-5 II s

The Pentax K-5 II s was measured at 29 ISO settings from ISO 80 to ISO 51200. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (80) read noise is 1.13 DN, or 3.3 electrons at the sensor. From ISO 2000 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Full well at base ISO is about 47,442 electrons; unity gain is around ISO 230.

Pentax K-50

The Pentax K-50 was measured at 28 ISO settings from ISO 100 to ISO 51200. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 0.59 DN, or 7.2 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 1250 don't change analog gain (digital push). Full well at base ISO is about 49,740 electrons; unity gain is around ISO 1210.

Pentax K-5 II s vs Pentax K-50 read noise table

ISO	Pentax K-5 II s	Pentax K-50
80	1.125	–
100	1.310	0.590
125	1.602	0.637
160	1.853	0.697
200	2.297	0.895
250	2.868	1.035
320	3.317	1.206
400	4.170	1.485
500	5.205	1.840
640	6.105	2.144
800	7.727	2.676
1000	9.849	3.411
1250	11.632	3.972
1600	15.348	4.408
2000	11.632	5.464
2500	13.833	6.277
3200	18.126	7.210
4000	23.588	9.254
5000	27.858	11.392
6400	36.504	13.929
8000	47.505	17.877
10000	56.886	22.471
12800	72.505	28.246
16000	91.773	35.506
20000	110.661	42.814
25600	142.025	54.569
32000	178.527	71.012
40000	212.306	88.035
51200	278.204	109.137

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