https://purengom.com/2009/10/22/dslr-%ec%9e%85%eb%ac%b8-%ec%82%ac%ec%a7%84%ec%9d%80-%ec%9e%a5%eb%b9%84%ea%b0%80-%ec%b0%8d%ec%96%b4%ec%a3%bc%eb%8a%94%ea%b2%8c-%ec%95%84%eb%8b%88%eb%8b%a4/