Nick wrote:
After roller painting some plastered walls in a hallway / stairwell,
I've noticed that when looking across them as opposed to at them that
there are light and dark patches. Windows perpendicular casting light
across them may make the effect more noticable. Suspecting human error
at first I assumed that this was simply uneven painting but it doesn't
appear to be. Now I think that it may be due to the finish of the
plaster / paint being slightly different in some places and scattering
the light differently, but I've no idea what to do about it. We tried
lightly sanding a test patch to see if this made any difference, and it
may slightly, but sanding the walls, which are 3 or 4 meters high in
some places seems like a bad idea and likely to create more unevenness
that moves the patches elsewhere or even makes it worse; sanded walls
do have a much nicer finish than roller painted though.

So I'm wondering how to get a better or different finish that looks
even from any angle, and any suggestions much appreciated! The paint is
Super Leytex high opacity matt emulsion, and rollers the usual default
roller that comes with painting trays. It's frustrating as the walls
look fine when viewed more directly, but looking across them cannot be
avoided from some parts of the hallway and so the patches are generally
noticable.

How many coats did you apply ?
Simon.