I haven't worked with SMT's much, and have been trying to learn about the
codes. However I can find no information on the small caps that have no
printing on them whatsoever. The only variation I can detect between them is
slight variations in color, and some variation in thickness.

Example picture he http://www.cox-internet.com/kenb2002/smt_caps.jpg

How does one determine the value of these caps?

Thanks.