What is the minimum pixel size for a drop shadow in Illustrator CC

Question

I am creating an app icon that has a drop shadow.

When I resize the icon to some smaller pixel sizes to use in an app (around 20 x 20 pixels) the object transforms fine except for the shadow. I have checked the 'Scale Strokes & Effects' box in the transform window.

It seems the minimum size for the offsets of the drop shadow is one pixel regardless of what I type in the drop shadow box for yoffset and xoffset.

Is there anyway to get the shadow effect on a very small object? I know it will hardly be noticeable for such a small object but I prefer not to delete the shadow every time I resize the object.

Answer 1

You shouldn't really be limited by the minimum size of a drop shadow. The minimum value you can use is 0.01pt, which even at maximum zoom is essentially too small to see.

The drop shadow effect is a raster effect though, so what you are limited by is the document's raster effects resolution setting, and of course your output size.

Take the following 100 × 100 pt square with 2 pt drop shadow:

Resized to 5 × 5 pt (with effects scaled), gives you this:

The problem isn't the size of the drop shadow itself but the resolution at which it's being rasterized. If we go to Effect → Document Raster Effects Settings and increase the resolution, we get a more reasonable drop shadow effect:

And increasing the resolution further gives us something closer to what we began with:

Keep in mind that the raster effects resolution is a document setting, not per-effect.

If your final output is going to be a raster image then you're obviously limited to the pixel size of that output, so keep that it mind. It's a good idea to work at the correct size and turn on pixel preview periodically to see how everything will look.