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F2 
F1.8 
F1.6 
F1.4 
F1.2 
F1.1 
F1 
z 


2z 


4z 

(1+1/3)z = (4/3)z 
(1+2/3)z = (5/3)z 

(1+1/3)2z = (8/3)z 
(1+2/3)2z = (10/3)z 








y 
(3/4)y 
(3/5)y 
(1/2)y 
(3/8)y 
(3/10)y 
(1/4)y 
F1 passes 100% more light than F1.4 and F1.4 passes 100% more light than F2. This means that a factor of 2 can be used in light intensity from F2 to F1.4 and from F1.4 to F1; or a factor of 4 from F2 to F1.
F1.8 passes 1/3 more light than F2, and F1.6 passes 2/3 more light than F2.
F1.2 passes 1/3 more light than F1.4, and F1.1 passes 2/3 more light than F1.4.
We are talking about the light that passes to the sensor depending of the F factor.
But we can also think about the minimum illumination parameter and use the same principles: if at F1 passes 100% more light than F1.4 means that the minimum light required at F1 would be half than F1.4.
The line in green in the table indicates this.
Example: Min illumination at F1.6 = 0.04 lux
I will calculate it for F1.2
F1.6 = (3/5)y = 0.04 à y = 0.066 lux à the min illumination at F2 is higher than F1.6 (which makes sense)
F1.2 = (3/8)y = (3/8) * 0.066 = 0.024 lux à the min illumination at F1.2 is lower then F1.6
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