Lag Time

Vincent Bockaert, 123di.com

Lag time is the time between you pressing the shutter release button and the camera actually taking the shot. This delay varies quite a bit between camera models, and used to be the biggest drawback of digital photography. The latest digital cameras, especially the prosumer and professional SLR's have virtually no lag times and react in the same way as conventional film cameras, even in burst mode.

In our reviews we record "Lag Time" and define it as three distinct timings:

Autofocus Lag (Half-press Lag)


(Prime AF/AE)

Many digital camera users prime the autofocus (AF) and autoexposure (AE) systems on their camera by half-pressing the shutter release. This lag is the amount of time between a half-press of the shutter release and the camera indicating an autofocus and autoexposure lock on the LCD/viewfinder (ready to shoot). This timing is normally the most variable as it is affected by the subject matter, current focus position, still or moving subject, etc.

Shutter Release Lag (Half to Full-press Lag)


(Take shot, AF/AE primed)

The amount of time it takes to take the shot (assuming you have already primed the camera with a half-press) by pressing the shutter release button all the way down to take the shot.

Total Lag (Full-press Lag)


(Take shot, AF/AE not primed)

The amount of time it takes from a full depression of the shutter release button (without performing a half-press of the shutter release) to the image being taken. This is more representative of the use of the camera in a spur of the moment "point and shoot" situation. The Total Lag is not equal to the sum of the Autofocus and Shutter Release Lags.

This article is written by Vincent Bockaert,
author of The 123 of digital imaging Interactive Learning Suite
Click here to visit 123di.com