10-25-2007, 04:19 PM
Let's talk about IR Shift first. IR Shift is the difference in focal points for a lens under white and IR lighting. The more you zoom in on an object, the more IR Shift becomes noticeable.
IRC lenses correct IR Shift making both visible and IR rays focus on the same point, so eliminating the need for adjustment.
In the past we have to determine whether day or night-time images were more important and are expected to settle for an unfocused image for part of the day.
If 24 hours observation is required and it is based on IR rather than street lighting or floodlights, then IRC lens becomes a must for performance. Similarly, an application that uses pre-sets will normally need an IRC lens since images during IR illumination with pre-sets chosen in daylight will be blurred.
IRC lenses correct IR Shift making both visible and IR rays focus on the same point, so eliminating the need for adjustment.
In the past we have to determine whether day or night-time images were more important and are expected to settle for an unfocused image for part of the day.
If 24 hours observation is required and it is based on IR rather than street lighting or floodlights, then IRC lens becomes a must for performance. Similarly, an application that uses pre-sets will normally need an IRC lens since images during IR illumination with pre-sets chosen in daylight will be blurred.