When creating a drop shadow for objects, what is the traditional / classic “rule” for the offset direction? I see so many that are down and right, which results in the light source coming from the top left.
However, I read somewhere (I don’t remember where, maybe an old David Siegel post from years ago) that when adding drop shadows to text, the shadow offset should be down and left, which provides a slight dark edge to the leading edge of the text, enhancing readability.
Or is the rule just “be consistent”?
Just to be clear, I’m asking if there’s a design “principle” that has been established through tradition or precedence.
In your designs of your own devising, be consistent. If one object has a top-left light source, then all of your objects should have a top left light source.
In designs of others’s devising, you need to be consistent with their format. In the case of Apple’s Mac OS X (per the HIG), drop shadows come from the top-center, and actually a bit on the front around a 45˚ angle, and not from the side.
As for the direction, that is largely dependent on the effect you are trying to achieve, but as an informal rule based on not-so-casual observation, the light-source is typically on the top-left casting a bottom-right shadow. David Siegel may technically be correct, but it is almost entirely subjective in the end.