Raw histogram and why does it matter

For maximising the quality of the raw data you need to maximise the exposure* within your DOF and blur constraints without clipping important highlights. In that case ISO is irrelevant for me, as long as important highlights are not clipped because I set the final image lightness in post, not in camera.

If I am ETTR'ing I lock in base ISO, all other times ISO is set to Auto for the above reason.

* exposure - amount of light striking the sensor per unit area while the shutter is open
** optimal exposure - the maximum exposure* within dof and motion blur requirements without clipping important highlights.
*** under exposed - more exposure* could have been added with the DOF and blur constraints still being met without clipping important highlights.

true, but we are looking for the surface thats going to give you a good start. here is the histogram of the surface in direct sunlight. its not 100% but boy its close.

What happens if within the entire FOV there is not an object that is lighter than that surface what could you do then, I would further increase the exposure

I don't need a surface to give me a good start. I just set the maximum exposure* within my DOF and blur constraints without clipping important highlights. The camera can set ISO where it likes as long as important highlights are not clipped. I then set the final image lightness in post.

You don't need any surface to do that. It's very straight forward.

* exposure - amount of light striking the sensor per unit area while the shutter is open
** optimal exposure - the maximum exposure* within dof and motion blur requirements without clipping important highlights.
*** under exposed - more exposure* could have been added with the DOF and blur constraints still being met without clipping important highlights.

Or heaven fore bid that there is an object that could cause clipping in the green channel like some leaves or grass, would you not have to adjust your exposure to eliminate that clipping. You do realize that you can have clipping in non white objects

i thought grass was good to but its not

we are not worried about clipping and highlights but purely the perfect mid tone , because that's what bobs histogram is designed for.

I used to use sunlit grass for in camera metering when I first started out and was shooting sooc jpegs only. Sunlit grass was still very hit and miss depending on the lighting and the colour of the grass.

But to maximise the quality of the raw data you don't need sunlit grass or any other surface as I described earlier.

is it sunny where you are atm ?

You clearly don't know how a person goes about ETTR and maximizing exposure, It is not about setting your target exposure over a target that meters over an object that is 3 stops lower from saturation of the sensor, for the majority of the time it is about where the highlights and more importantly
the clipping point of the three channels as I have said you can have clipping in a color channel that is not on a neutral target.
What happens if in your scene nothing falls near 2 stop greater than 12.7% grey this would allow you to further increase your exposure an additional stop over what you are already doing. It is about protecting your highlights from clipping and these highlights can be in color objects

IliahBorg RD is designed about finding where the clipping points in the color channels are
Where Mid tones fall come from how you process the image

totally agree.

Sunlit grass was said to be a good surface for approximate metering but it is very hit and miss.

i understand that.

I'm having my own fun using an incident meter. But, I know you'll have plenty of fun without me.

not my understanding , his program is measuring by default the 12.5 % midtone at EV0

Then it doesn't matter whether it is sunny here or not.

Ok im going to give it away now only because i just went into the studio and shot my Hand in my normal position for head shots and then run it through bobs program and my midtones are PERFECT Im the man 😎😎😎
do me a favor and shoot the palm of you hand in any auto exposure mode ,view it in bobs program and it should have the EV0 perfectly in the middle of you readings , hope that makes sense. you dont win a lolly pop 😁