I have been wondering if the following is true and the implication for mirrorless cameras. DSLR camera sensors are only exposed to light when the picture is taken, so the sensor presumably produces less noise than if it was always exposed to the light. I find support for this in the way Canon warns about Live View extended usage. Is this true?
If this is true, then how do mirrorless camera deal with the extra noise from the sensor?
To my knowledge and experience sensors don't produce more or less noise by being exposed continuously allowing the use of live view.
The exposure time for actual pictures is still exactly the same, and so is the amount of noise generated.
Canon most likely warns against using live view because it has to keep the mirror lifted up and will also drain way more battery than usual.
I have used a canon DSLR, a Fuji Mirrorless and now a Sony SLT. The last two continuously use live view (Sony has a fixed mirror system that reflects light to the focus system but lets most trough to the sensor).
Comparing shots between those and a regular DSLR I see no noise difference not explained by newer and better technologies.