Why calibrate digital cameras and lenses?
Although modern manufacturing processes of both cameras and lenses help ensure quality and consistency this is by no means a guarantee especially when combining camera body to a lens. Intolerances do occur and the subsequent results can be that images look soft at best and at worst completely out of focus. These intolerances can be caused by a variety of different reasons, be it manufacturing errors, misaligned lens optics, loose lens or body mounts to name a few. These inconsistencies can either be camera (auto focus module related) or lens related or a combination of the two. This error is often referred to as a front or back focusing error Front focus errors This occurs when the camera / lens and focus module incorrectly focuses in front of the chosen focus point (nearer the camera) Back focus errors In this instance the camera / lens and focus module incorrectly focuses behind the chosen focus point (further from the camera). The camera manufacturers are aware of these errors and as a result offer the user the ability to correct using AF Micro adjustment (Canon) or AF Fine Tune (Nikon) and Focus Settings (Sigma) Using this method, photographers are able to correct for any front / back focus issues and as such ensure that both camera and lenses and perfectly matched thus producing the best possible results.