How to NOT -- DIY.

I have one (for now) gripe with almost all of the "fix-it" home design / repair / DIY TV shows. NONE of these shows show the correct way to PAINT walls with a roller. The painters are seen going this way & that, up, down, side-to-side. The camera comes in after the paint has dried and you can SEE a difference in the surface reflectivity from different parts of the same painted wall.

WRONG ANSWER !!!!

The Right Way:
You first paint the trim & corners, making sure you come several inches out onto the wall surface. THEN, with the roller, you arbitrarily choose a section of wall that is 3/4 the width of both your outstretched arms and 1/2 the height of your raised arm holding the roller. You start with a fairly full roller of paint, and paint a 'W' or 'X' into the center of this arbitrary area you have chosen. The idea is to get several slightly thicker ribbons of paint distributed across the chosen area. You will use these "ribbons" as the source of the paint you will be distributing onto this chosen area. From the initial 'W' or 'X', you paint back and forth, up and down, until the thicker paint from the initial 'W' is distributed as evenly as humanly possible across the entire area you are currently working on.

You then move onto the next section, overlapping at least eight inches (or a roller width) onto the previously painted area. You completely paint one wall at a time. When you think you have evenly covered one wall in the paint of your choice, you have one more task.
Your roller must be lightly painted. I.E., you must have just finished the last section of the wall of the room you are painting. DO NOT PUT ANY MORE PAINT ON THE ROLLER JUST NOW. You grip the roller firmly but VERY LIGHTLY. Starting at almost touching the ceiling, and in the LIGHTEST TOUCH you can possibly do, roll the roller in a straight line, from ceiling to floor down a "single strip" of wall. BARELY touch the wall. A single stroke, at a quick speed from top to bottom. Repeat this, with about an inch overlap, across the entire freshly painted surface of the wall.

The concept is simple. The same exact pressure, the same exact direction, and the same exact amount of paint in these final "finishing touches". This is what guarantees EXACTLY the same grain & finish to the entire surface of the wall.
This is what makes the Sun, or any light from fixtures reflect perfectly across the entire surface of the wall. No changes in reflectivity, or pattern, or albedo. Perfection. The same principle as brushing velvet very lightly, in one direction.

Very simple. It requires a little practice. But your painted walls will have NO roller stroke marks, and the painted surface will look exactly the same across all of your walls. No matter what light, from what direction, or whatever intensity.

Try it and see.