Whether OD’s beyond six should be claimed is currently a matter of dispute. However, scientists usually concur that it is more appropriate to mark high density filters with the symbol >6, which means an OD of six or more. Some manufacturers claim OD’s up to 20, which includes some questionable extrapolations. If a laser is so powerful that an OD above six is recommended, full body armor may also be required. After all, an OD 6 filter will allow only one 10,000th of a percent of the original laser light to pass through.
