So let’s take a look at the unit conversion
between contrast ratio and EV span.
The contrast ratio directly refers to the dif-
ference in light intensity. Double that number
means double the light. So you have a linear
unit.
Exposure values are in a logarithmic scale.
Each increase by 1 doubles the light, meaning
it also doubles the ratio number. It’s very easy
to convert in one direction. It goes like this:
2^exposure values = contrast ratio
For example, if you have a dynamic range
that spans 12 EVs, that is 2¹² = 4096. So, that
DR can also be called a contrast ratio of rough-
ly 4000:1.
Converting in the other direction is a bit
more tricky. You need to calculate the base
2 logarithm, or the binary logarithm as the
scientists call it. Chances are your desktop
calculator doesn’t have a “log₂“ button. Mine
doesn’t, not even the one on my computer.
There is just a regular “log” key, but that refers
to log₁₀ instead of log₂. But luckily, by a happy
math coincidence, there is a fixed conver-
sion factor. Well, actually it is a math law that
says, There shall be 3.321928 used here. Usu-
ally 3.32 is all the precision we need. So, that
would be as follows:
EV span ≈ log₁₀(contrast ratio) * 3.32
For example, 4000:1 simply means
log₁₀(4000) * 3.32 ≈ 12 EVs.

Ну зачем они ещё и *книги пишут*, ну зачем... =___=

#oteeon

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