There’s a temptation to go crazy with the effects that PowerPoint has in it’s arsenal.
While there are certainly many cool things you can do, some of them are real enemies of making a scientific poster that is easy to read. Chief among these effects is text shadow, in my opinion.
Sometimes a shadow is a nice touch on a title, it dresses it up. Shadow can also be used to make type more visible against a variable background, like a label on a picture. When white type runs through a white section of the picture, the shadow makes it visible.
Where shadow never makes sense is on all the text in your text boxes. It just makes it harder to read. Our eyes want to read text as nice sharp black against white. Putting a fuzzy shadow behind it confuses your eyes.
Part of the reason for this is that we tend to use serif type such as Times New Roman in text boxes. The pointy ends of serif type lead your eye from one letter and word to the next. However, shadows on this kind of text really get in the way of easy reading. They take your eye on a confusing side trip, and can also make letters hard to distinguish.
The picture shows examples of a title with a jazzy maroon shadow, and regular size type with a shadow. Notice how hard the Times New Roman text is to read.