Shutter lag is the time difference between when you press the shutter button, and when the shot is actually taken. There are many reasons behind the shutter delay time. There are technical issues that cause a shutter lag as well as manual mistakes because of which there is a shutter delay. There are ways to solve shutter lag to an extent, but completely eliminating is almost impossible. If we take the technical aspects of a shutter-lag, there are two main processes that cause it. Following we have listed both the processes  that cause shutter lag.

The two main processes that cause Shutter Lag are:

1. The root cause of a shutter lag is the time taken by your camera to auto-focus. Until your camera finds the correct focus for the shot, it isn't ready to snap a picture and thus it results in shutter delay. On most of the point-and-shoot cameras, focusing is a slow process because it uses a motor to move the lens and fins a correct focus spot. On SLR and DSLR cameras it is comparatively faster than what it is on pint-and-shoot cameras.

2. Time for the Shutter Release. The time that your camera takes to open the camera shutter ( It is either a physical  or an electronic shutter) and the time that it takes to prepare its sensors for the shot. This time when combined with the processing time, focusing time etc. results in shutter lag. The time you camera takes to focus on a subject is the longest amongst all.

Shutter lag time also varies from camera to camera. The more expensive and advance your camera is, less shutter lag delay there will be. It is more prominent in inexpensive cameras. The general rule of thumb to reduce shutter lag is that you should never shoot in full Auto mode. Instead, switch to a mode that lets you pre-set functions.diminish.