Spool,
You may as well get technical and figure out the exit pupil if talking about how objectives and magnifications influence light transmission. Exit pupils are the cone of light able to exit the optic and into your eyes. It's calculated by the objective diameter divided by the magnification.
I have a 1-4*24 PST which is a light, compact short-range scope. At max magnification the exit pupil is 4mm (24/4 = 6mm). The pupil of a human eye is roughly 4.5mm during daylight and dilates to 7mm at night. At max magnification you are getting 6mm of light through the scope; great for daylight and pretty good for night, but 4x is not a huge magnification. At close range this is not an issue however. Your eyes can take and want more light at night. A larger scope has the potential to exit more light so you can have higher magnifications but still see well at night. A compact NF 2.5-10*42 on 6x has a 7mm exit pupil...perfect for both day and night shooting. If you crank it up to 10x its not so good for night shooting but perfect for daylight shooting.
The more you crank it up the less field of view so it's a bunch of trade-offs.
The quality of glass is also a factor in light transmission.
You may as well get technical and figure out the exit pupil if talking about how objectives and magnifications influence light transmission. Exit pupils are the cone of light able to exit the optic and into your eyes. It's calculated by the objective diameter divided by the magnification.
I have a 1-4*24 PST which is a light, compact short-range scope. At max magnification the exit pupil is 4mm (24/4 = 6mm). The pupil of a human eye is roughly 4.5mm during daylight and dilates to 7mm at night. At max magnification you are getting 6mm of light through the scope; great for daylight and pretty good for night, but 4x is not a huge magnification. At close range this is not an issue however. Your eyes can take and want more light at night. A larger scope has the potential to exit more light so you can have higher magnifications but still see well at night. A compact NF 2.5-10*42 on 6x has a 7mm exit pupil...perfect for both day and night shooting. If you crank it up to 10x its not so good for night shooting but perfect for daylight shooting.
The more you crank it up the less field of view so it's a bunch of trade-offs.
The quality of glass is also a factor in light transmission.