This difference may be significant or it may not. If it is you will need to use another system. Video systems are more accurate and easier to use for very exact measurements. There are three general types of video measuring systems, video filars, interactive video and fully automatic. Each has its uses and problems and manufacturers make a wide range of each system.
All video systems use a video camera, mostly black and white.
The camera is connected to a computer or digital system, think of it as a black box. The black box does something and out pops the magic number. You see all of this on the monitor. This means that you have to set the microscope up for video. If the microscope isn't set up properly the system will be very difficult to use.