Diko said:
Sharlin said:
Similarly, as I implied before, pixel size matters because larger pixel area means deeper wells means more electrons means more current means more power means more heat to dissipate.
Not sure about the wells size correlation to the the power drain (ergo heat issues). Feel free to share some info. I'll be more than glad to learn something new.
My understanding is that ADC (the ones off the sensor) should take the heavy load. But since not the complete 30Mpix are used its load should be far easier to process. As for current usage I believe it is correlated to ISO sensitivity and fps, but still not in the case where at least half of the sensor is not used. Interesting, indeed.
PS:Where is one
JRISTA when you need him :/
Technically speaking, sensors work in the voltage domain. Voltage implies potential, but it does not necessarily mean current flows. Additionally, effectively regardless of ISO, because of gain, after the initial pixel amplification the total voltages the rest of the sensor (and off-die electronics, if there are any analog components off die) works with the same general total charge.
If the pixel FWC at base gain is 60ke-, then you are going to be working with a range of charge up to 60ke- regardless. If you are working at 2x the base gain, then your pixel range drops to 30ke-, however a gain of 2 will scale that back into the 60ke- range before anything else happens with it. So, the amount of current involved won't be changing much. And the current used here is minuscule to start with, it's an electronic integrated circuit with micron-scale transistors.
The camera itself may draw 7-9 volts, however most of that potential would be for handling mechanical stuff like focus. The circuitry itself is probably operating either in the 5V or possibly even 3.3V domain (logic circuitry usually cannot work off of high voltages.) High quality, low noise regulators would be used to clean up the power and deliver a pure DC current to the logic circuitry as well.
Heat has to do with the amount of energy dissipated. That entirely depends on how much resistance is in the circuits. Resistance is intrinsic in every component, every wire, but the right use of the necessary materials can minimize resistance. Minimizing trace lengths can reduce wire resistance. If the circuitry is designed to operate with minimal resistance, using minimal trace path lengths (i.e. by locating most of the circuitry on the sensor die, as close to the pixels as possible), operating at the lowest frequency possible, it will dissipate minimal heat. That is a matter of sensor design. Canon has not been on the cutting edge of sensor design for many years, so who knows if they have been able to integrate all the necessary technology on-chip to minimize head during video readout. Most sensors that use fully on-die readout systems, with column-parallel ADC (Sony, Panasonic, OnSemi and I think Aptina all have this technology) are able to operate at lower readout frequencies to achieve the same readout performance, and the entire readout pipeline is very close to the pixels, which means less heat generated.
If Canon is still using off-die ADC units, my guess is they will have to operate things at a higher clock frequency, they will have to move charge around to much greater distances, and all of that will generate more heat under continuous readout.