Factors affecting physical mapping

Another factor affecting the mapping pattern is the source design. Short-arc (xenon and metal halide) lamps can be considered point sources, which generate bulls-eye patterns whereas long-arc lamps (xenon and fluorescent) will produce oblong patterns. Low-resolution mapping tends to obscure these differences, which are real. How pertinent these results will be to an individual study will depend on a number of factors, one of which will be the samples physical size. 

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