What method did you use to arrive at this figure?
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Assuming a 16:9 aspect ratio is used across PUBG and CS, I take this to mean PUBG has the following horizontal scope FOVs:
ADS: 70
2X: 44.44
4X: 20
8X: 11.03
15X: 6.67
Am I interpreting this correctly? If so, this appears to follow the reasoning that the scope magnification values listed on pubg.me are true, and that they're applied to a base 80 FOV:
ADS: 70
2X: 80 ÷ 1.8
4X: 80 ÷ 4
8X: 80 ÷ 7.25
15X: 80 ÷ 12
What steps, if any, have you taken to verify the accuracy of your stated scope FOV values?