[HDRI] Re: Relationship - Outdoor illumination value, HDR pixel, value, ISO, Shutter Speed and fstop

[Seth Rossman]

I don't know where you are trying to go with this, but it would take 
some pretty expensive equipment to get a true evaluation.

Just putting low end cameras near the same place will not capture the 
same scene--even with the same manufacturer.

Remember, these are "F" stops, not "T" stops; they are not as precise 
from lens to lens.  They do not need to be.

Seth