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

Input-referred read noise at base ISO: Pentax K-1 II 3.3 e⁻ (ISO 100), Pentax K-3 2.9 e⁻ (ISO 100).

Pentax K-1 II

The Pentax K-1 II was measured at 40 ISO settings from ISO 100 to ISO 819200. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 1.11 DN, or 3.3 electrons at the sensor. From ISO 160000 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 204800 don't change analog gain (digital push). Full well at base ISO is about 48,634 electrons; unity gain is around ISO 300.

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 II vs Pentax K-3 read noise table

ISOPentax K-1 IIPentax K-3
1001.1101.919
1251.3572.395
1601.5482.770
2001.9193.458
2502.3784.287
3202.7514.993
4003.3876.233
5004.1997.835
6402.4129.126
8002.94911.551
10003.86414.621
12504.28717.268
16005.27817.148
20007.21022.162
25009.00026.538
320010.92834.060
400015.03244.324
500016.79552.710
640022.78568.120
800033.12888.035
1000034.776105.420
1280049.180132.514
1600072.505171.255
2000073.009205.074
25600101.829238.856
32000150.123306.555
40000148.056364.557
51200209.383467.882
64000321.795–
80000292.036–
102400418.766–
128000634.730–
160000600.491–
204800891.444–
256000873.098–
320000955.426–
4096001,260.692–
5120001,595.729–
6400001,937.526–
8192002,256.702–

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Data: Photons to Photos · © William J. Claff