A method, comprising: monitoring a material web in a first operating mode of a machine vision system comprising at least one lighting device (18, 19), at least one image sensor (12, 15) and a data processing device (13, 16), wherein the monitoring in a first operating mode comprises illuminating the material web by said at least one lighting device (18, 19) using a first type of illumination and capturing images of the material web by said at least one image sensor (12, 15) at a first image capturing frequency, and wherein the material web is arranged at least partly on a machine clothing; transmitting the captured image data of the captured images to the data processing device (13, 16) for analysis; and if absence of the material web on the machine clothing is detected from the image data captured in the first operating mode by the data processing device (13, 16), the method further comprises: changing the machine vision system for monitoring the machine clothing in a second operating mode and for transmitting the captured image data of the captured images to the data processing device (13, 16) for analysis, wherein in the second operating mode said at least one image sensor (12, 15) is reconfigured to capture images at a second image capturing frequency from the machine clothing to be monitored, and the data processing device (13, 16) is arranged to detect deviations from the image data captured of the machine clothing with image analyzing parameters reconfigured to be suitable for detecting deviations in the machine clothing to be monitored, characterized in that in the second operating mode intensity of light of at least one lighting device (18, 19) is increased or decreased for enabling effective detecting of deviations from the machine clothing. monitoring a material web in a first operating mode of a machine vision system comprising at least one lighting device (18, 19), at least one image sensor (12, 15) and a data processing device (13, 16), wherein the monitoring in a first operating mode comprises illuminating the material web by said at least one lighting device (18, 19) using a first type of illumination and capturing images of the material web by said at least one image sensor (12, 15) at a first image capturing frequency, and wherein the material web is arranged at least partly on a machine clothing; transmitting the captured image data of the captured images to the data processing device (13, 16) for analysis; and if absence of the material web on the machine clothing is detected from the image data captured in the first operating mode by the data processing device (13, 16), the method further comprises: changing the machine vision system for monitoring the machine clothing in a second operating mode and for transmitting the captured image data of the captured images to the data processing device (13, 16) for analysis, wherein in the second operating mode said at least one image sensor (12, 15) is reconfigured to capture images at a second image capturing frequency from the machine clothing to be monitored, and the data processing device (13, 16) is arranged to detect deviations from the image data captured of the machine clothing with image analyzing parameters reconfigured to be suitable for detecting deviations in the machine clothing to be monitored, characterized in that in the second operating mode intensity of light of at least one lighting device (18, 19) is increased or decreased for enabling effective detecting of deviations from the machine clothing.