Horizontal Lines Across Stairs Area - Am I being stupid?

[JimmyB18]

Evening all,

Slightly random post and not sure if this is anything to be worried about or not, but I noticed some discoloured 'lines' going across horizontally in the stairs area of our house. There are no cracks at all, and it's only really visible in certain lighting, but now I've noticed them I can't stop looking at them when the light is on!

They're not clear on the picture, but they're underneath the black lines I've marked out on the picture below.

Any ideas what it could be?/if this is a problem?

Any help would be much appreciated.

 

[Old Salt]

Turn the light off

 

[Deleted member 174758]

Possibly the telegraphing of a joist position if as I suspect the lines are near the top of the stairs.

 

[John D v2.0]

Board joints? Or where the plasterer's arm stretched to when they finished it? Most walls look terrible when a light shines across the surface though, make the light softer would be my suggestion.

 

[Alec_t]

Plasterboard joints beneath skim?