Howard sent this picture, wondering whether it was a walnut orb weaver, or a melanic garden spider. My dictionary describes melanic as "unusual darkening of body tissues caused by excessive production of melanin, esp. as a form of color variation in animals" in case the word is new to you.

I'm sure he's right that it's a melanic garden spider (araneus diadematus) thanks to the classic cross of white blobs on its back. It's also a great close up photo.