Measuring and controlling image luminance

General
1

Dear Magic Leap community, I have a pupillometry experiment (in Magic Leap) with 2 colored image conditions. I want to measure image luminance of all of my images to: 1) check if there are significant luminance differences between my 2 conditions and 2) be able to account for luminance in my analyses to ensure that any pupil size differences * condition are not due to luminance differences. I have tried measuring luminance with GIMP and in MATLAB (in 2D), but I am not getting convergent results and struggling to find what the gold standard approach would be in vision research / how can I get the best luminance measures of my stimuli on Magic Leap. Thanks a lot!!

PS: I already have extracted the ambient light sensor data from my experiment, but as I understand it this is measuring ambient light rather than light measured through the lenses (where you can see the objects presented).

2

Hi Apy,

Are you using linear or gamma space measurment with your app? If linear: The engine is doing the math linearly, but the display still applies a hardware gamma (typically ~2.2) If gamma: The engine and display are both working in non-linear curves.

You may need to calculate for the gamma curves to get the “true” intensity of the light.

Thank you,