Abstract: A method and apparatus for analyzing features in a field which is scanned to produce video signals according to the spectral characteristics of the features. The apparatus incorporates two or more filters for producing different spectral characteristic images of the field which are then synchronously scanned using a plurality of separate scanners which are synchronized but which need not be so accurately registered point by point as is normally the case with color scanners. The invention provides for the use of an anti-coincidence detector circuit to associate video signal information arising from scanning non-registered images of the features in the field so that the information in the separate channels can be associated and made available for simultaneous comparison so that a ratio can for example be obtained of the integrated optical density measurements of a feature in respect of different color components of the image of the feature.