Note: In this series of lessons only manual methods of images editing will be described. Plug-ins will not be touched because they are not multipurpose and totally illegal. (Please show me the person who has the license.) And every respected professional should be able to edit images manually. 

Theory

Shadows are considered to be one of stumbling blocks for all designers. They usually judge the quality of works as well as designer’s level of mastering from the shadows. There are some stereotypes or so called rules of good forms that we are judging the quality of shadows from.

Besides, statement that photorealistic shadow is good and non-photorealistic shadow is bad is totally incorrect. Very often one has to correct and adjust photorealistic shadow in order to get a clear and qualitative element of site design. Also one should have to sketch out a shadow in order to emphasize an important block or a menu.

Below you can find three main rules on shadows imaging.

Rule 1: Shadow should not be a mud

Pictures below show how shadow should not be made. Too sharp changes from white to black are shown here. Such changes are quite rare while natural daylight.

And I have considered first rule here

Shadow here is much brighter and transparent. It does not draw attention back. Shadows as on the Pic 2a and Pic 2b are commonly used at corporate sites. And it is of no good that designers take it as a feature of a bad form.

Exception:
If it is night on the picture and our object is lightened with a lamp, shadows are very contrasting then. It all depends on lightening. In this lesson we talk about common case, when the daylight is used.