why the new fluorescent lamp feels lower brightness?

[Diyerget]

Hi all.
I just bought a box of T12 40w new fluorescent lamp that feels lower brightness than the existing one, why?
I don't know how to measure the brightness, just feeling.

thanks
Diyer

 

[James]

could be that they are a different colour to the last one.
the white, cool white and daylight seem much brighter than the warm white.

 

[Marvo]

Fluorescent tubes also have 'triphospher'' versions. If the old tubes were triphospher versions they would have been up to 20% higher lumen output for the same wattage, they would also have had better colour rendering.
Also as James mentioned the new tubes may be slightly different colour, warmer colours will appear dimmer than cooler colours ie a tube with ba 3000K colour will appear a bit dimmer than one with a 3500K colour.