Babu - please post some photo's (as an example) and stop raising theoretical threads.

All lenses will affect the light that passes through them - this is not news.
Then the film/sensor will only record a portion of the light received.
Post processing will change things further.
So what?

Mate - get out take some photos, post them for CC here in 'members' photos' and you will learn at least 1,000 times more about photography than by posting threads like this. Seriously!

Also: Why not have a look at some photos and offer a Constructive Critique of those images, that also helps you learn.