The mobile and Smartphone camera market is driven by consumers' desire for better picture quality. Auto-flash is the most common flash mode setting used by consumers on their smartphones. Auto-flash technique is used in modern cameras to turn on the flash light automatically when the light level is lower than a pre-defined level. The auto-flash activation light level varies among different cameras but should be set to a value that provides a balance between good picture quality and less battery consumption. There is no published methodology on how to determine the correct light level for auto-flash activation, so I developed one based on Signal to Noise Ratio analysis, SNR10, and image sharpness analysis that determines the light settings for autoflash mode. Then the aforementioned method was tested using the Apple iPhone and Samsung Galaxy. Finally, I determined the auto-flash light activation level for these phones using this methodology.