I have explained this for pages here and at getdpi but people just won't listen but instead defend their superiority of ISO 35 hard...
Yunli,
I don't think anyone is really arguing the point that the raw data is the same for ISO 35, 50 and 100. As is so often the case with these debates, it seems to be one about semantics and tact. I happen to be in the BJL camp here. I don't see ISO 35 as a "fake" ISO. I see it as the only ISO that is "real". All the other ones are "fake." Therefore, I think of ISO 35 as the base ISO, and 50/100 (and all the others) as some sort of push. I think this is supported by the DXO graph. It is the ISO standard that leads me to this view. You may choose to look at it differently, which is fine by me. Just please don't bother trying to convince me that your perspective is the only one that is correct.
This is an interesting position for me to take because I've owned an IQ180 since they were first released (ordered Apr-2011 delivered Aug-2011). Some may remember when this back was first announced the base ISO was not 35. It was an early firmware release that provided the option for 35 ISO.
I do not agree with your position that this is some conspiracy on the part of PhaseOne. As Bernard stated, all this isn't rocket science; learn how the camera / back / histogram / metering works and shoot accordingly. I don't see this any differently than the old Velvia debate. Was it really ISO 50, or was it ISO 35 film?? Those who loved the saturated colors used it at 50. Those who wanted a more neutral result used it (carefully) at 35. Was 50 a conspiracy on the part of Fuji? Not to me, but think what you want.
You state your definition of proper exposure is to check with RawDigger. While I understand and appreciate that, as a landscape photographer I find it particularly difficult to do that in the field. What I do is use both ISO 35 and ISO 100. In order to be efficient for me I use ISO 35 when I am worried about shadow detail, and ISO 100 when worried about blowing highlights. I'm sure that sounds ridiculous to you, but that keeps me moving when the light is changing fast. I don't have a light meter in the field at all so I rely on my head and the histogram, which needs to be interpreted (especially my head).
What I find amusing about all this is the two photos below. I took these while backpacking in the Wind Rivers. Although I've posted them in other threads, I think they are useful in getting a point across. The first image was taken at sunset with IQ180/Alpa STC/90hrsw ISO 35. The second image was taken the next morning with Sony a7r/Leica 90 summicron ISO 100. Why did I use the Sony in the morning? Was it because I was worried about the wide dynamic range of this shot? No, it was because it was cold, I was in a hurry and I had a miserable sleepless night because of a nasty headache and buffeting winds against the tent all night. I figured I would drop half of the Alpa gear in my state at the time.
The point is at the end of the day it is the Sony image that has blown highlights and struggles with the dynamic range of the scene. So all of this debate pales in comparison to what subjects you like to shoot and what conditions you have to deal with.
To the OP I would offer this: If you are worried about highlights, use ISO 100. If you are worried about shadows use ISO 35. But most of all, do what gives you the best results given your workflow.
Dave