Hey there,
Unfortunately, there's no hard answer to the question. Buffer swirl
can be found or seen under a variety of lighting condition. When
I first started out with machine polishing, I worked under flourecent
light. I thought my work was good as I could not see any defects;
that is, until I rolled the car outside. For these reasons, I find it is always
a good idea to have as many different light sources
as possible; whatever you miss under flourecent will be picked up
by incandencent, whatever is not picked by halogen is picked up
by sunlight, etc.
To me the light sources that best pick up buffer swirls are sunlight
and elevated metal halide bulb (street lights).
Improving your buffing techniques also works wonders for reducing
buffer marks. And when that fails, you can step up to the cyclo
or PC.
