flood's input lag measurements

[Sparky]

Light to dark transitions are a lot harder, I'm lucky to get within 500 microseconds.

Edit: Interestingly, the 20microsecond pulse of light is visible to the eye, but the 500 microsecond pulse of darkness is not.

[stirner]

That's persistence. Ignoring phosphor persistence, we stop noticing non-illuminated phases at about 80Hz, i. e. 12.5ms.

[spacediver]

Detecting a single pulse of darkness requires the ability to temporally sample the visual field with a precision that meets or exceeds the duration of that pulse. Look up flicker fusion thresholds, and temporal integration/summation. Since a detector, such as a photoreceptor in the retina, responds to light, and not to darkness, being able to detect a single pulse of darkness means being able to distinguish, in time, two temporally separate light events. The whole system has to be able to (neurally) encode those two events as distinct, rather than sum them together.

Detecting a single pulse of light only requires the ability to encode a single event, and that is limited by luminance, or contrast thresholds. If the single pulse of light was bright enough, you could detect a pulse that was one nanosecond long.

[Sparky]

That's persistence. Ignoring phosphor persistence, we stop noticing non-illuminated phases at about 80Hz, i. e. 12.5ms.

I know, I'm talking about 0.5ms pulses at 1hz. I think it's just down to the eye being less sensitive to changes in brightness of something that's already bright.

[flood]

Wikipedia says it takes several milliseconds for a photoresistor to detect, but that's just saturation, you start to see the change immediately. Using a photoresistor, a pot, and a LED, I was able to get down to the noise (<20 microseconds ) between turning a LED on and detecting it with the photoresistor(just adjusting the threshold).

yea but i want to be able to detect the light fron a single line from my crt, which is way dimmer than an led

[flood]

just ordered more crap from digikey in hopes of improving the performance further. gunna try a battery pack as well to see how much noise is related to usb power.

also hilarious discussion on ocn:
http://www.overclock.net/t/1546025/skyl ... -cursor/30

[Sparky]

just ordered more crap from digikey in hopes of improving the performance further. gunna try a battery pack as well to see how much noise is related to usb power.

also hilarious discussion on ocn:
http://www.overclock.net/t/1546025/skyl ... -cursor/30

I saw that thread, and stepped in it. Now I need to find a hose.

As for noise, Wouldn't being hooked up to USB for data make that a moot point? I'd try sticking a big cap on your power rail first.

[flood]

yea that'd work too but i also want to reverse bias the photodiode

[Sparky]

I just read some more of that thread...I'm dying of laughter.

"But it's not a mouse!!!"

[Black Octagon]

My world would be much better if I could put the entirety of OCN on ignore. Never understood why people continue to post there.