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Since the manufacturer didn´t give the spectral distribution information, I will approximate LED as a monochromatic one (using the 460 nm peak).

From the datasheet, the LED intensity range goes from 6 lumen to 30 lumen. For the 6 lumen case, I used scotopic eye sensitivity curve (i want to apply the stimulus in a dark room) to convert the lumen value to radiant power (W). I simply divided the 6 lumens per the sensitivity times the 1700 normalization coefficient. Is this process right? I reached a value of 0.006W.

I know from the ray tracing software that only 3.7º of the LED (total from the center) reach the pupil. So, from the spacial LED curve, the 0.006W become approximately 1.57×10−4W (i traced a trapezium over the graphic and divided the areas)

The illuminated retinal area is 0.0031cm2

So I calculated the irradiance dividing the 1.57×10−4W by the area of 0.0031cm2, having a value of 0.05W/cm2

However, I need this value in log photons/cm2/s

Can you validate my logic? Thanks!