I have been mulling this over for quite a while, and searching around the web, essentially coming up with more questions than answers.
Let me take the (M)anual exposure mode as an example. Shutter Speed (say 13 sec), Aperture (f1.8) and ISO (1600) are dialed in and fixed, with an EV bias of 0. Just to make this a bit interesting, let's use a real world example of shooting the Milky Way (no GPS tracking), where the shutter speed really can't be more than about 13 seconds in order to limit star trails (within about 3 pixels), the aperture needs to be essentially wide open to collect as much light as possible, and the ISO needs to be relatively high, but as capped as low as possible to reduce noise.
If an EV bias were to be applied, just how is the camera body going to apply it - given that everything else is fixed?
- Is it going to boost by an extra bit, the amplification of the signal coming off the sensor - essentially increasing the ISO? or,
- is it going to be applied in some other way down stream in the image processing chain?