tint problem

[magister]

had my dealer install tints sa car ng wife ko.

ang usapan, 3M BC20 sides and back, BC35 front.

i got the car in the evening so i really could not tell if all was ok. the following morning when i got to look at the car, parang hindi BC20 yung sa backglass. sa tingin ko BC35 yung kinabit kasi hindi ganun ka-mirrorized yung likod. my wife says sa angle lang daw siguro ng salamin. am not convinced kasi with that reasoning. tingin ko nagkamali yung installer. question is how do i show/prove this?

[shotgun]

use a piece of white bond paper and place it behind the windows and then windshield... take note of the color shading. if they used the correct tint you requested, you will notice one will look darker than the other.