Pentax K-1 vs Pentax K-3: read noise comparison

Input-referred read noise at base ISO: Pentax K-1 3.1 e⁻ (ISO 100), Pentax K-3 2.9 e⁻ (ISO 100).

Pentax K-1

The Pentax K-1 was measured at 30 ISO settings from ISO 100 to ISO 204800. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 1.20 DN, or 3.1 electrons at the sensor. From ISO 320 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 51200 don't change analog gain (digital push). Full well at base ISO is about 41,653 electrons; unity gain is around ISO 250.

Pentax K-3

The Pentax K-3 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 1.92 DN, or 2.9 electrons at the sensor. From ISO 1600 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 20000 don't change analog gain (digital push). Full well at base ISO is about 24,761 electrons; unity gain is around ISO 150.

Pentax K-1 vs Pentax K-3 read noise table

ISO	Pentax K-1	Pentax K-3
100	1.197	1.919
125	1.444	2.395
160	1.659	2.770
200	2.042	3.458
250	2.532	4.287
320	2.928	4.993
400	3.605	6.233
500	4.595	7.835
640	5.352	9.126
800	6.727	11.551
1000	8.634	14.621
1250	10.196	17.268
1600	13.086	17.148
2000	17.630	22.162
2500	19.973	26.538
3200	25.992	34.060
4000	34.060	44.324
5000	40.224	52.710
6400	51.984	68.120
8000	68.594	88.035
10000	79.341	105.420
12800	103.968	132.514
16000	138.141	171.255
20000	158.683	205.074
25600	206.500	238.856
32000	266.871	306.555
40000	315.173	364.557
51200	404.501	467.882
102400	809.002	–
204800	1,606.828	–

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