need help answering the following questions
1) how many uncompressed a7r3 raw stills can fit in a single 64gb card and 128gb card
2) can the a7r3 uhs2 slot use a uhs1 card and can the uhs1 slot use a uhs2 card. aware that the performance won't be the best and might sound funny if I actually put in a uhs2 card in the wrong slot but I just wanted to know if it will actually work. the 2 card in the 1 slot and the 1 card in the 2 slot
3) can the original a7s eyepiece fit on the a7r3?
4) here's the biggie question
the reason I moved from an apsc 7d to a full frame a7s is because of iso performance. if i remember correctly apsc sensors capture the image let's say on iso 100 but because they actually have a smaller physical size they actually gather less light BUT because iso 100 needs to be a certain brightness due to the iso standards, the camera then needs to brighten the picture post capture. this leads to increased noise levels perceived. Now if I have an a7s or a7r3 and I mount let's say a 10 to 18 e mount for apsc. then I shift it to apsc mode. will i be right that the brightness of the image captured will not be altered by the camera making an iso 100 capture a real iso 100 capture?
I hope I made sense