Its width directly proportional much light passes lens.The wider , light comes in.It measured numbers attribute of.You remember aperture numbers work better reverse.A wider aperture means ’ lower f-number.In adjusting aperture camera , usually take photos low lighting , although normally useful utilizing standard kit lens.The reason pieces glass set maximum aperture.More often , usually measurement f/3.5 , usually wide enough job.It usually aperture around f/1.8 suitable well-exposed low-light photo.It produces shallow depth field also capable catering light four times aperture f/3.5 can.SHUTTER SPEED The next thing take look controlling exposure low-light setting shutter speed .