Phototransistor speed

I tried a phototransistor instead of an LDR. Look at the speed difference! The scale here is different (far faster sampling) which means that the phototransistor is at least 50x the speed of the LDR.

I'm designing a multi-channel colour sensor which will have 4 colour sensors controlled by a single AVR ATMEGA48.
* Each sensor has 3 LEDs red, green, blue.
* Each of these LEDs is turned on in turn, the ADC is then sampled approx 4 times and some filtering is done on the returned signal. The signal is then corrected for differences in phototransistor sensitivity etc by applying a simple gamma correction to give reasonably matched RGB values.

Using phototransistors should make this all fast enough to operate 4 channels at 100Hz or so.

100Hz sampling should be fast enough for an NXT robot.