Canon EOS Rebel T6i EF-S 18-55mm IS STM Lens Kit Instruction Manual - Page 139

3 Setting Noise ReductionK 2 Set the desired setting.  Select the desired setting, then press .  [Auto] For exposures of 1 sec. or longer, noise reduction is performed automatically if noise typical of long exposures is detected. This [Auto] setting is effective in most cases.  [Enable] Noise reduction is performed for all exposures of 1 sec. or longer. The [Enable] setting may reduce noise that cannot be detected with the [Auto] setting. 3 Take the picture.  The image will be recorded with noise reduction applied.  With [Auto] and [Enable], the noise reduction process after the picture is taken may take the same amount of time as that for the exposure. You cannot take another picture until the noise reduction process is completed.  Images taken at ISO 1600 or higher may look grainier with the [Enable] setting than with the [Disable] or [Auto] setting.  With [Auto] and [Enable], if a long exposure is shot with the Live View image displayed, "BUSY" will be displayed during the noise reduction process. The Live View display will not appear until the noise reduction is completed. (You cannot take another picture.) 139