Ok I did an inspection today on an asphalt shingle roof with numerous problems such as cracked and broken shingles. The installer left part of the black on the shingle exposed I believe for appearance purposes as the whole roof is done this way with the exception of one area where no black is shown. My initial reaction is improper overlap is causing the cracking due to flaps not adhering properly. Roof is 7 years old. I feel that the install is faulty but would like a second opinion.