First and foremost, I'm not entirely sure if this is the proper place to post this question, so I apologize if there's a better section for this.
I am looking to determine the effect of changing the PWM frequency of a light source, LED for example, has on the perceived brightness to the human eye.
As an example, say you have an LED operating at 80% duty cycle at a frequency of 200 Hz. Keeping the duty cycle at 80%, but increasing the frequency to 400 Hz, does the human eye perceive these two situations as the same brightness? What about a larger increase, to say 1 kHz or 10 kHz?
I have have tested this using an ATmega328p and two LEDs. I had one LED at 80% duty cycle at 122 Hz. The other LED starts at 80% duty cycle at 30 Hz (yes there is a very noticeable flicker), then with the press of a button, it changes the frequency. The values used are 30, 122, 245, 490, 980, 3920, and 31370 Hz.
While it wasn't exactly what I was after, I took light measurements using a BTS256-LED from Gigahertz Optik. Aside from 30 Hz, which I attributed to the flickering, it appeared changing the frequency had no effect on the amount of lumens that the LED put out.
Then I tested in both a light and dark environment, and I was not able to discern any difference while changing the frequency.
I have done a lot of searching and reading, and I've learned a ton about PWM, LEDs, flicker, heat dissipation, sensitivity to light color/brightness, and much more. Unfortunately none of it is what I'm looking for.
Looking for any kind of insight here. Perhaps this is a bad question, and I'm barking up a tree that doesn't exist. Or perhaps the answer is either very obvious, indicating my findings from my test were accurate, or far more complex than I realize.
I appreciate any and all responses, as I'm out of ideas/topics to look for more information.