Normal Maps Affecting Shader Brightness

[dj_buckley]

Is it normal - excuse the pun - for a normal map to alter how bright a material appears?

I've just done two tests side by side and the brightness change is clearly visible when sliding between just displacement vs displacement + normals?

I've zoomed into 1 pixel and sampled the colour and it does indeed change the values.

Displacement only looks fine.  Displacement + Normals looks duller.

What I can't figure out is whether the reduced brightness is a side effect of the extra perceived detail from the Normal map, or if it's just how Normal Maps work, or if it's not working properly.  Lack of technical knowledge as to how normal maps work isn't helping me.

I've attached the two version for comparison.

[Aram Avetisyan]

Yes, normal maps affect where a face/pixel is directed at, which can alter the brighness depending on the lighting. On a more diffused lighting (e.g. solid white color without any lights) the brightness difference will become less.

[dj_buckley]

Yes, normal maps affect where a face/pixel is directed at, which can alter the brighness depending on the lighting. On a more diffused lighting (e.g. solid white color without any lights) the brightness difference will become less.

Perfect thanks for the easy to understand explanation.

I've just tested it with a less agressive normal map with some flat spots and the flat spots don't change value.