Pentax 645Z vs Pentax K-1: read noise comparison

Input-referred read noise at base ISO: Pentax 645Z 3.5 e⁻ (ISO 100), Pentax K-1 3.1 e⁻ (ISO 100).

Pentax 645Z

The Pentax 645Z was measured at 34 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 1.19 DN, or 3.5 electrons at the sensor. From ISO 640 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 2500 don't change analog gain (digital push). Full well at base ISO is about 48,430 electrons; unity gain is around ISO 290.

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 645Z vs Pentax K-1 read noise table

ISO	Pentax 645Z	Pentax K-1
100	1.189	1.197
125	1.474	1.444
160	1.670	1.659
200	2.099	2.042
250	2.585	2.532
320	3.010	2.928
400	3.758	3.605
500	4.691	4.595
640	5.426	5.352
800	6.821	6.727
1000	8.574	8.634
1250	9.987	10.196
1600	12.553	13.086
2000	16.336	17.630
2500	19.427	19.973
3200	19.973	25.992
4000	25.992	34.060
5000	31.125	40.224
6400	38.586	51.984
8000	50.213	68.594
10000	59.714	79.341
12800	59.714	103.968
16000	77.708	138.141
20000	92.411	158.683
25600	119.428	206.500
32000	154.343	266.871
40000	184.823	315.173
51200	213.783	404.501
64000	276.282	–
80000	328.557	–
102400	424.612	809.002
128000	548.748	–
160000	652.575	–
204800	837.532	1,606.828

Popular comparisons

All cameras · Open the full tool