Well one more "opinion" can't hurt so I'll chime in. I think you're on to something there Aster in that the 12vdc and the 48vdc would need to be handled differently as you point out. Maybe someone on here knows what is done? The 48 might go through a dc to dc conversion like an inverter?
One note on your comment, oscilloscopes don't measure current or microamps. They display voltage on the Y-Axis vs time on the X-Axis. Voltage not current. Would you agree?
But it is the best theory yet!
Of course the oscilloscope does not measure or display current, every electronics engineer knows that. However if you pass the supply through a very small resistor and measure the voltage drop on that resistor, then you can measure AND display the current drawn from the camera. HIK cameras use PoE Mode B with +48-56V at pins 4 and 5 of the Ethernet plug and the -V at the pins 7 and 8. The communication is also at 100Mbps level. The 12V supply from the pig tail does not go through any special conditioning electronics. It is the cleaner power supply compared with the PoE method. That's why some people do not see the pixels pulsating when the camera is fed with 12V.
On the other hand, the PoE supply goes through the isolation transformers of the Ethernet intrenal in the camera. Since these transformers are very small in dimensions, they have very thin coil windings that create voltage drop when current is drawn from the camera. This voltage drop has a form of spikes which must be filtered in order not to reach the rest of the electronics. This can be done with a very sophisticated electronic power conditioning circuit that adds cost to the camera. The alterative solution would be to have a better quality ethernet isolation transformer. That would also add cost to the camera. Another solution would software image proccesing. Even that has its own cost an complexity and in fact it tries to cover the problem, not solve it. So both proper solutions add cost.
Remember that in order of higest cost the most expensive items in electronics are power supplies, transformers, and capacitors (that age quickly).
In a nutshell, quality costs and quality can not always be defined in high level protocol specifications.
