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

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

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

ISO	Pentax K-3	Pentax K-3 II
100	1.919	2.000
125	2.395	2.479
160	2.770	2.908
200	3.458	3.580
250	4.287	4.469
320	4.993	5.169
400	6.233	6.498
500	7.835	8.168
640	9.126	9.580
800	11.551	12.126
1000	14.621	15.348
1250	17.268	18.001
1600	17.148	18.126
2000	22.162	23.588
2500	26.538	27.858
3200	34.060	36.002
4000	44.324	46.851
5000	52.710	55.715
6400	68.120	72.004
8000	88.035	93.701
10000	105.420	110.661
12800	132.514	141.044
16000	171.255	182.278
20000	205.074	215.269
25600	238.856	252.476
32000	306.555	326.288
40000	364.557	390.722
51200	467.882	497.999

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