I've recently painted a room using primarily a roller, and for the edges (corners, skirting boards, ceilings), I've used a brush.
Where the paint was applied with a brush, it is considerably darker than where it was panted with a roller.
As you can see, there are dark "areas" around the wall join, and the joint with the ceiling. I'm shining a very bright torch as it demonstrates the problem better, hence the odd looking shadow at the bottom of the image.
I've asked a handful of very experienced people I know who have painted many rooms (all DIYers, but still), and they all concluded that the paint wasn't applied thick enough on the wall itself, and that actually the problem is not the joints, but the main area of the wall which was applied with a roller. Upon hearing this, I was slightly shocked since the dark areas actually look like they are not well adhered, but I played along and re-applied the whole room using a roller with a third, then forth coat, and the same problem persisted.
At that point, I decided I was right, and that it is the areas around the corners. I've now been out and purchased a much smaller roller, which has allowed me to cover the corner areas with great success, and now they have been painted with that the problem has disappeared entirely, except for the very thin slithers around the edges where I have a 5-10mm gap which I daren't touch with a roller, even if I mask, since I'm going to make a really big mess, the roller won't roll properly, it will grind on the ceiling (even masked) and leave streaks... It's just not a good move, I can feel it going horribly wrong and being very frustrating already.
The question I'd like to ask is how can I achieve the same finish using a brush as I did using a roller. I would imagine the problem is something to do with the pattern a roller leaves reflecting light in a certain way, since that would fall in line with my experiments so far. Naturally I could just roller them very carefully and re-paint the ceiling and skirting, but that defeats the object. I want them looking good, and I've done this before without problems.
Can somebody explain the physical problem, and possibly suggest a solution to it? I'm 5 tins of paint deep at this point, and it should've been a 2 tin job at most if I hadn't been misguided so badly.