but from what I can tell it doesn't looks like "real" products use them very often, instead they use light sensor ICs like this:
even though they're more expensive, and sometimes more complicated to use. Can anyone tell me why? Are the ICs better at evaluating light than the photoresistors? I've found that photoresistors aren't particularly fast, but for many/most applications (like a TV backlight) speed isn't that important. Is it a RoHS compliance thing?
In the end it all depends on the requirements of the project:
speed // how fast
accuracy // typical error
precission // the numbers of digit
power consumption // (milli)watts
startup time // second
etc
what to choose and that is true for every component. Be aware that your total accuracy is often the sum (or worse) of the accuracy of individual components.
In addition, resistive photosensors contain Cadmium (they are "CdS", or cadmium sulfide) which is a banned substance under the RoHS directive (and probably elsewhere), thus they cannot be incorporated into consumer equipment if it is to be sold where RoHS or similar standards exist.
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The Ruggeduino: compatible with Arduino UNO, 24V operation, all I/O's fused and protected