Nikon D4 vs Nikon D40X: read noise comparison

Input-referred read noise at base ISO: Nikon D4 16.2 e⁻ (ISO 100), Nikon D40X 17.8 e⁻ (ISO 100).

Nikon D4

The Nikon D4 was measured at 31 ISO settings from ISO 50 to ISO 204800. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 2.25 DN, or 16.2 electrons at the sensor. From ISO 10000 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 25600 don't change analog gain (digital push). Full well at base ISO is about 118,209 electrons; unity gain is around ISO 720.

Nikon D40X

The Nikon D40X was measured at 6 ISO settings from ISO 100 to ISO 3200. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 2.17 DN, or 17.8 electrons at the sensor. From ISO 400 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 33,411 electrons; unity gain is around ISO 820.

Nikon D4 vs Nikon D40X read noise table

ISO	Nikon D4	Nikon D40X
50	2.114	–
64	2.099	–
80	2.114	–
100	2.250	2.173
125	2.235	–
160	2.479	–
200	2.313	3.482
250	2.445	–
320	2.603	–
400	2.928	6.233
500	3.249	–
640	3.837	–
800	4.317	11.551
1000	5.169	–
1250	6.233	–
1600	6.774	23.264
2000	8.056	–
2500	9.580	–
3200	12.126	46.527
4000	14.723	–
5000	18.765	–
6400	21.112	–
8000	26.909	–
10000	30.910	–
12800	38.854	–
16000	46.206	–
20000	53.446	–
25600	67.649	–
51200	134.364	–
102400	268.727	–
204800	537.455	–

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