In order to avoid differences in any microlens angle effects for wide angle light paths we set the aperture of the lens to F11.
We use a 10nm Ha filter and OIII filter. The reference camera selected in this experiment is QHY22 which uses the SONY ICX694 CCD sensor. The QE can be found on various websites. We use the data in http://www.astrosurf.com/buil/cameras/index.html as reference data
From this curve we know the absolute QE of ICX694 is 67% at OIII and 58% at Ha.
Test conditions
QHY600 Gain=30 (mode 0) System gain=0.37e/ADU Pixel size=3.76um*3.76um Pixel Area=14.1376um^2
QHY22 Gain=0 System gain=0.29e/ADU Pixel size=4.54um*4.54um Pixel Area=20.6116um^2
Ha Test results with different exposure times
Exposure

QHY600 Measured ADU

QHY22 Measured ADU

1S

5305

5753

2S

8895

11373

3S

12682

16977

4S

16355

22551

5S

19903

28112

6S

23534

33651

7s

27542

39147

8s

31282

44574

9s

34925

49457

10s

38910

54291

Using a linear fit we determine the response of the QHY600 is 3726.3 ADU per second and the QHY22 is 5434.8 ADU per second per pixel.
Multiple by the system gain: The QHY600 is 1378.6e/sec/pixel and QHY22 is 1576e/sec/pixel.
And divide by the pixel area: The QHY600 is 97.51e/sec/um^2 and QHY22 is 76.47e/sec/um^2.
It shows on the same exposure and area, for the converted electron, the QHY600 has 1.27 times more than QHY22. Since the QHY22 QE is 58% at Ha, the QE of QHY600 is 58%*1.27=74%
OIII Test Results with different exposure times
Exposure

QHY600 Measured ADU

QHY22 Measured ADU

1s

8109

8776

2s

14916

17421

3s

21131

26011

4s

27550

34597

5s

34233

43091

6s

40443

51201

Following the same method as we did for Halpha we find:
QHY600: 6458.3*0.37/14.1376=169.02e/sec/um^2
QHY22: 8506.3*0.29/20.6116=119.68e/sec/um^2
The ratio of QHY600 to QHY22 is 1.41. So, the QE of QHY600 in OIII is 67%*1.41=94.5%
Elsewhere Christian Buil states a lower value of the IMX694 QE at 486nm to be 62% at Halpha to be 54% (http://www.astrosurf.com/buil/CMOSvsCCD/index.html). If we substitute these figures as the reference QE, the results for the IMX455 would be 87.4% at OIII and 68.6% at Halpha. We therefore conservatively estimate the peak QE of the IMX455 to be greater than 87%.