There are two kinds of video image sequence distortions caused by vibration of the camera. The first is the vibration of the line- of-sight, causing location changes of the scene in successive frames. The second distortion is the blur of each frame of the sequence due to frame motion during its exposure. The relative effects of these two types of degradations on the ability of observers to recognize targets are investigated. This study is useful for evaluating the amount of effort required to compensate each effect. We found that the threshold contrast needed to recognize a target in a vibrating video sequence under certain conditions is more affected by the motion blur of each frame than the oscillation of the line-of-sight. For digital sequence restoration methods, this study determines the required precision of the deblurring and registration processes. It shows that the deblurring process should not be neglected, as it often is.