I don't have a great picture but I installed a full length ridge vent and it works great. It consists of a plastic vent that fits the entire length of the roof. Prior to installing, a 1-2" cut is made into the top most shingles & roof exposing a 1-2" gap (you will be able to see into the attic). After that, the plastic ridge vent is installed, after that, ridge shingles are installed on top of the vent. The open gap is from end-to-end of the roof except 2' on each end. When all done, I had a 70' vent which is virtually invisible.
During the summer, if you go into the attic, it sounds like a big wind storm up there as the air is blowing straight up and out.
This is the only photo I have here at work and this is as I just started installing.
Photo showing plastic ridge vent with a few ridge shingles nailed to it - just starting:
Photo below is "before" gap is cut into ridge:
