Hugnot
Well-Known Member
Glass & coating quality. Some of my 40mm objective lens scopes are brighter & transmit more light than some of my 50mm objective lens scopes, both set at the same power. Generally, Leupold is a good deal.
Perceived brightness:
Perceived Brightness = cube root of realistic light gain
"Perceived brightness is the perception of target light thru the scope relative to the perception of the amount of target light with a single un-scoped eye. Perceived brightness is calculated as the cube root of light gain which is the basis for computer color space brightness scaling & is also the perceived brightness of a 5-degree target in the dark with a uniformly dark background."
Then it gets into stuff like the lumen gain difference between un-scoped & scoped eye light gain that reaches the eye pupil. Like if 1 lumen for un-scoped eye & 50 lumens for scoped eye (50 times more) the difference would appear to be 50**1/3 or 3.7 times as bright.
Low light performance:
"This calculation derives Low Light Performance as the average of light gain and resolution gain through magnification. as a measure of target image acuity gain in low light similar to Twilight performance specified by scope manufacturers. Low Light performance is much more useful than Twilight Performance as Twilight Performance is the average of just the objective lens diameter times magnification while Low Light performance is the average of the actual Perceived Brightness times magnification which includes the exit pupil/eye pupil relation, light transmission, approximated diffraction and perception of relative light gain. Resolution & contrast are not included. Lower quality optics will yield relatively less gains at higher magnifications."
My experiences are similar to tt35's. My Leupold 6.5-20X40 & 6.5-20X50 give good low light performance, better than comparable 20% lower priced Vortex scopes of similar magnification & objective size. No Razor's.
Imagine - dust covered rodents sitting on same color dirt in deep shade at 270 degrees (west) late afternoon. Next scope will be more spendy & brighter.
Elementary astronomy lession - never, ever look at the sun with your optic - it's that cube root stuff.
Perceived brightness:
Perceived Brightness = cube root of realistic light gain
"Perceived brightness is the perception of target light thru the scope relative to the perception of the amount of target light with a single un-scoped eye. Perceived brightness is calculated as the cube root of light gain which is the basis for computer color space brightness scaling & is also the perceived brightness of a 5-degree target in the dark with a uniformly dark background."
Then it gets into stuff like the lumen gain difference between un-scoped & scoped eye light gain that reaches the eye pupil. Like if 1 lumen for un-scoped eye & 50 lumens for scoped eye (50 times more) the difference would appear to be 50**1/3 or 3.7 times as bright.
Low light performance:
"This calculation derives Low Light Performance as the average of light gain and resolution gain through magnification. as a measure of target image acuity gain in low light similar to Twilight performance specified by scope manufacturers. Low Light performance is much more useful than Twilight Performance as Twilight Performance is the average of just the objective lens diameter times magnification while Low Light performance is the average of the actual Perceived Brightness times magnification which includes the exit pupil/eye pupil relation, light transmission, approximated diffraction and perception of relative light gain. Resolution & contrast are not included. Lower quality optics will yield relatively less gains at higher magnifications."
My experiences are similar to tt35's. My Leupold 6.5-20X40 & 6.5-20X50 give good low light performance, better than comparable 20% lower priced Vortex scopes of similar magnification & objective size. No Razor's.
Imagine - dust covered rodents sitting on same color dirt in deep shade at 270 degrees (west) late afternoon. Next scope will be more spendy & brighter.
Elementary astronomy lession - never, ever look at the sun with your optic - it's that cube root stuff.
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