Movement Correction

Introduction

Movement artefacts in video sequences can be corrected either automatically, or manually by dragging the mouse. Individual images, selected images, or the whole video sequence can be corrected. These functions can be accessed using , or the Tools menu when a video sequence window is active.

Although good results can be obtained, it always much better to try and make sure there is no movement in the first place, especially for velocity or fcf measurements.

Automatic Movement Correction

This function will try to automatically correct any movements in the video sequence. It uses a least squares fit pixel by pixel so it can take quite some time processing full frame video. It is best to experiment on a short (say 5 second) video sequence to get a feel for the performance on your computer. Calculation parameters can be changed using the Settings/Auto Movement Correction menu function. See Calculate Movement Correction

When using the Settings for Original method using full image method some parameters can be adjusted so that you can trade off between processing time and correction accuracy. See Movement Correction Settings

Manual Movement Correction

There are two methods of manually correcting movement, “Tracking” and “Dragging”

Tracking

This function allows you to track an identifying feature on the image using the left mouse button. It is better than the Dragging function for manually correcting movement in video sequences.

You may also want to slow down the playback speed to make it easier to react.

Move the video to your desired start position, then click down the left mouse button on some feature in the image that you can follow with the mouse. If you want to correct a sequence of images, keep the left button down, so that the total correction so far is remembered for following images, then press the ‘P’ key to play the sequence. Follow the movement with the left mouse button down as the video plays. Release the left mouse button as soon as you want to stop corrections. If the image has stopped moving around, you will probably still want to keep the left button depressed until you reach the end of the video so that the remaining images are corrected too.

Note that this method uses the distance of the mouse from the position of the left button click as an offset to adjust to the current image’s offset. When the button is released, no offset is applied. When you click again, a new offset correction is started.

Dragging

This function allows you to drag the image into the correct position using the left mouse button. It is probably most useful for correcting individual images, but can be used on sequences. If using on a sequence, it helps to have a dimension mark or line marking a feature than then be dragged back to the marking dimension line.

You may also want to slow down the playback speed to make it easier to react.

Move the video to your desired start position, then click down the left mouse button and drag the image to its corrected position. If you want to correct a sequence of images, keep the left button down, so that the total correction so far is remembered for following images, then press the ‘P’ key to play the sequence. Drag the image into position as the video plays. Release the left mouse button as soon as you want to stop corrections. If the image has stopped moving around, you will probably still want to keep the left button depressed until you reach the end of the video so that the remaining images are corrected too.

Note that this method uses the distance of the mouse from the position of the left button click as an offset to adjust to the current image’s offset. When the button is released, no offset is applied. When you click again, a new offset correction is started. See Manually Adjust Movement Correction

Reset movement correction offsets

Use the Reset offsets function in the Edit menu to clear all offsets back to zero. This works whether the offsets were created by the automatic or manual methods.

To clear just a range of images, first set the start and end image numbers in the Edit, Select images....