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

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

The Pentax K-3 II 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 2.00 DN, or 2.9 electrons at the sensor. From ISO 10000 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Full well at base ISO is about 23,907 electrons; unity gain is around ISO 150.

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

ISO	Pentax K-1 II	Pentax K-3 II
100	1.110	2.000
125	1.357	2.479
160	1.548	2.908
200	1.919	3.580
250	2.378	4.469
320	2.751	5.169
400	3.387	6.498
500	4.199	8.168
640	2.412	9.580
800	2.949	12.126
1000	3.864	15.348
1250	4.287	18.001
1600	5.278	18.126
2000	7.210	23.588
2500	9.000	27.858
3200	10.928	36.002
4000	15.032	46.851
5000	16.795	55.715
6400	22.785	72.004
8000	33.128	93.701
10000	34.776	110.661
12800	49.180	141.044
16000	72.505	182.278
20000	73.009	215.269
25600	101.829	252.476
32000	150.123	326.288
40000	148.056	390.722
51200	209.383	497.999
64000	321.795	–
80000	292.036	–
102400	418.766	–
128000	634.730	–
160000	600.491	–
204800	891.444	–
256000	873.098	–
320000	955.426	–
409600	1,260.692	–
512000	1,595.729	–
640000	1,937.526	–
819200	2,256.702	–

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