Nikon D40 vs Nikon D4S: read noise comparison

Input-referred read noise at base ISO: Nikon D40 11.9 e⁻ (ISO 200), Nikon D4S 15 e⁻ (ISO 100).

Nikon D40

The Nikon D40 was measured at 5 ISO settings from ISO 200 to ISO 3200. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (200) read noise is 1.96 DN, or 11.9 electrons at the sensor. From ISO 200 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 1600 don't change analog gain (digital push). Full well at base ISO is about 24,849 electrons; unity gain is around ISO 1210.

Nikon D4S

The Nikon D4S was measured at 34 ISO settings from ISO 50 to ISO 409600. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 2.07 DN, or 15 electrons at the sensor. From ISO 6400 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 12800 don't change analog gain (digital push). Full well at base ISO is about 113,218 electrons; unity gain is around ISO 730.

Nikon D40 vs Nikon D4S read noise table

ISO	Nikon D40	Nikon D4S
50	–	2.129
64	–	2.114
80	–	2.099
100	–	2.071
125	–	2.173
160	–	2.346
200	1.959	2.056
250	–	2.204
320	–	2.378
400	3.411	2.497
500	–	2.713
640	–	3.053
800	7.362	3.411
1000	–	4.000
1250	–	4.659
1600	14.420	5.816
2000	–	6.727
2500	–	7.945
3200	39.124	9.646
4000	–	11.876
5000	–	15.242
6400	–	16.679
8000	–	21.556
10000	–	24.590
12800	–	31.125
16000	–	39.124
20000	–	51.625
25600	–	63.558
32000	–	75.584
40000	–	94.353
51200	–	119.428
102400	–	240.518
204800	–	464.650
409600	–	797.865

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