OK, I know that ISO 100 is ISO 100 regardless of the equipment...I'm not disputing that..all I'm saying is that one camera may be able to process/expose an image correctly at 100 ISO while another camera may need to do the same thing correctly at 200 ISO (just like the example given by the original post)..so why is that so?? It must be the difference in the equipment. Let's say pixels are analogous to the size of a window in a room..a large window lets more light in, whereas a small window in the same room lets less light in..agree? Most full frame sensors have larger pixels in the given space, this is documented. Further, larger pixels receive a greater flux of photons over a given exposure time (at the same aperture), so their light signal is much stronger. Can we then conclude that they let more usable light into the camera, therefore a lower ISO setting may be sufficient to properly expose the image, therefore they can shoot that same scene at 100 ISO. So when 200 ISO is required on one camera, the higher end camera because of better sensor sensitivity, and better DSP capabilities may be able to accomplish the same result at 100 ISO.
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