Hi Stephen, sorry for the late reply. Some new film arrived today so I'm ready to repeat my testing and I now have time to think about this again.

Originally Posted by Stephen Benskin
Take a look at Ralph's Nomograph. Here are three questions to ask yourself.
Why is the aim negative density range for a "typical diffusion enlarger" 1.20 when the ISO standard has it as 1.05?
Actually when I look at his nomograph and read page 1 of the pdf Ralph gave us in this thread, the ISO target density range is 1.30, not 1.20. He goes on to explain why we don't target that. One reason is that "In general, advertised ISO film speeds are too optimistic and suggested development times are too long." also "Not knowing the exact combination of products we use for our photographic intent, they (the film manufacturers) have had to make a few assumptions."

Originally Posted by Stephen Benskin
If you draw a line from paper CI 0.58 through 7 SBR to 0.58 adjusted aveGradient SBR (middle scale), through Normal Camera Lens Flare and you get 0.58 for the approximate final avgGradient. How is it possible to have the same CI from beginning to end when normal flare is at least a stop?
How can 0.58 be the aim average CI when flare is zero, yet CI 0.58 is also normal using a 1 1/3 stop flare factor: 1.05 / 2.2 - .40 = 0.58?
To start with this nomograph something Kodak created and Ralph reproduced, so I'd prefer both of them justified it before I did.
It is possible the nomograph is in error since as you point out, 'normal' flare results in no adjustment in the CI. Alternatively there may be something 1/we don't understand about using it. I'd need Ralph to chime in here, or to see the original Kodak publication with any accompanying text.

As for you calculating 0.58 as normal when using a 1 1/3 stop flare factor and a SBR or 7 stops, you have used a target CI of 1.05 and I don't know where you got that from. If instead we assume a target CI of 1.30 as I mention above, and convert the 7 stops to the correct units by multiplying by 0.3 to then the adjusted CI =(1.3/(2.1-0.4))=0.76, not 0.58.

You posted 2 other replies, coincidentally one only 1 hour ago which I haven't had time to digest, so I will have to reply to those at a later time.