Alphabet Soup? Help

[dancqu]

EVs and ZONEs most obviously. Dan

 

[john_s]

How do you generate CI? if the SBR is 5 and the DR is 1.25 - what is the CI? and how do you get it - also - I know from my step wedge that my grade 2 paper can print a DR of 1.25 - What if I do a kalitype - I need a DR of 1.75? I am always reading about CI differences from AZO to Silver to Alt process. How do you calculate CI?

The CI is the fraction DR/ER where the term ER is the Exposure Range as a log(base 10).

In this example, the ER is 5 x 0.3 = 1.5. Each "stop" is an exposure difference of 0.3. Another way is to say the brightness range is 32 (2^5) and log(base 10) of 32 is 1.5 (actually 1.505 if you want to be unnecessarily fussy). DR is already in log(base 10) units.

So CI = 1.25/1.5=0.83

 

[gainer]

As a matter of interest, sensitivity of human vision is pretty much logarithmic. The just noticeable difference between two brightnesses is a nearly constant ratio. There's a lot more to it than that, but it's a good approximation over the usual range of adaptation.

 

[fhovie]

Thanks John

The CI is the fraction DR/ER where the term ER is the Exposure Range as a log(base 10).

In this example, the ER is 5 x 0.3 = 1.5. Each "stop" is an exposure difference of 0.3. Another way is to say the brightness range is 32 (2^5) and log(base 10) of 32 is 1.5 (actually 1.505 if you want to be unnecessarily fussy). DR is already in log(base 10) units.

So CI = 1.25/1.5=0.83