Sony A7RM2 DR-Pix Read Noise
Prepared 2015-08-29 by Bill Claff

 

This article presents analysis results only. For background see Sony A7S DR‑Pix Read Noise.

The Sony A7RM2

 

This table summarizes the calculations for all of the ISO settings:

 

model

measured

ISO

pixel

conversion

conversion

intermediate

conversion

conversion

read

read

Setting

noise

gain

noise

noise

gain

noise

noise

noise

 

e-

e-/e-

e-

e-

DN/e-

DN

DN

DN

100

0.925

1.000

2.906

3.050

0.315

1.223

1.555

1.413

125

0.925

1.000

2.906

3.050

0.397

1.223

1.721

1.666

160

0.925

1.000

2.906

3.050

0.500

1.223

1.955

1.964

200

0.925

1.000

2.906

3.050

0.630

1.223

2.277

2.329

250

0.925

1.000

2.906

3.050

0.794

1.223

2.712

2.778

320

0.925

1.000

2.906

3.050

1.000

1.223

3.286

3.357

400

0.925

1.000

2.906

3.050

1.260

1.223

4.032

4.045

500

0.925

1.000

2.906

3.050

1.587

1.223

4.993

4.918

640

0.925

6.350

2.906

6.553

0.315

1.223

2.399

2.418

800

0.925

6.350

2.906

6.553

0.397

1.223

2.874

2.940

1000

0.925

6.350

2.906

6.553

0.500

1.223

3.497

3.555

1250

0.925

6.350

2.906

6.553

0.630

1.223

4.305

4.356

1600

0.925

6.350

2.906

6.553

0.794

1.223

5.343

5.318

2000

0.925

6.350

2.906

6.553

1.000

1.223

6.666

6.737

2500

0.925

6.350

2.906

6.553

1.260

1.223

8.346

8.433

3200

0.925

6.350

2.906

6.553

1.587

1.223

10.474

10.310


You can see by examining the table or the following chart that the model read noise and the measured read noise agree quite well.
(This is a log-log chart and the small discrepancies are generally well within a 1/6EV tolerance.)
However, agreement above ISO 3200 diverges as if there is a small amount of noise reduction. This is still under investigation.

Conclusion

I have demonstrated that to characterize read noise of the A7RM2, incorporating DR-Pix technology, that only three values are required: 0.925e- pixel noise, 2.906e- pixel conversion noise, and 1.223DN ADC conversion noise. (And unity gain of 318 to compute the conversion gains to feed in.)

Addendum

This chart shows graphically how measured read noise (in DN) drops steadily below the model above ISO 3200 (EVS 10)