Are there any easy to obtain and fast responding photoresistors out there ? The resistance of material must decrease when light in shining on it, and the response must be fast. Note: I know that photodiodes respond extremely fast but they must be used coupled with a transistor to amplify the detection. Also photodiodes response is not decrease in resistance but generation of voltage. I use a cheap CdS photoresistors but they are too slow, especially when going from light to dark.