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This Week's Finds in Planning is the blog of Martin Krieger, Professor of Planning at the University of Southern California's School of Policy, Planning, and Development.

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Smartphone Cameras for Urban Documentation

Most smartphones not only have cameras, but will attach GPS coordinates to the EXIF file, readily used for mapping. But the camera quality is varied.\

My iPod Touch 4th gen camera is not very good (5th should be much better)

Galaxy Nexus camera is ok (but people say it is not so good) 5Mpixel

Nokia 808, with 35 Mpixel camera, is terrific. The lens is remarkably good--custom made aspherical, fixed f stop, big sensor for phone. But no one will get an 808, since its system, Symbian Belle, is the end of the line.

So: Do a test with your camera and your smartphone. You can readily see if the difference matters, since if you are photographing printed stuff, how well it is legible is obvious.

My work is mostly outdoors or in reasonably lit indoor situations, so low light performance is not crucial. It's nice to have a zoom, but I almost always am shooting at the wide angle. And the biggest concern is whether the shutter speed is fast enough, that is whether you can adjust the ISO so that you get a fast shutter speed, but do not mind the noise.

Again, my purpose is documentation. Can I read detail on the sign half way down the block, or 25 ft away indoors? Depth of field is usually substantial since the f/stop is large and the focal length is not too small. It's better to have a larger sensor and a better lens, but the best camera is the camera you have with you, and your smartphone camera may do for most of your work.

I have been using a GPS equipped point and shoot 14Mp camera (Casio?),.one of the early ones, for my City Heights, San Diego work. I now realize that the 808 phone would be quite good, maybe even much better, but the Galaxy Nexus might not be good enough. I don't know about the latest iPhone, and will leave it to others to test: 8 Mp is usually quite good.

The problem always is in the design of the lens. Most lenses for most cameras, conventional and smartphone, fall off substantially in quality toward the edges and corners. Aspheric lenses can do much better.

The 808's aspheric lens is in fact almost as good in the corners as in the center, and in fact it is very very good all the way. Every element is aspheric (one element is dimpled!), the lens has to operate for only one f/stop, f/2.4, and the lens has four or five elements. Hence, the designers had enough play to make a terrific lens. Since it is molded plastic (there may be one glass element, I am unsure of this), once you get the molds done it is inexpensive to make the elements, and not too difficult to place the lens elements precisely. Moreover, the whole lens moves to focus, rather than having additional internal focusing for closer distances, as is the case for the best 35mm camera lenses that offer aspherics (the Leica 50mm f/2 Aspheric Summicron). You cannot make such plastic lenses for larger cameras than the smartphones' since the plastic expands too much with changes in temperature.