# Grab the background image

Aim

To create a background that you can use to draw arenas and zones.

Procedure

1.Choose Setup > Arena Settings > New or right-click Arena Settings in the Experiment Explorer and select New.

Result: The Grab Background Image window opens.

2.If you track from video, click Browse and open a video file. In the Video window, if possible, browse to a video frame without animals. Then click Grab.

If you track live, if possible, remove the animal from the arena and click Grab.
Noldus Calibration Card Note: Optionally, you can use the ‘Focus Assist’ and auto-calibration with the ‘Noldus Calibration Card’. Please follow these steps before grabbing your background image

3.Check that the aspect ratio of the background image is correct, and if necessary, adjust it (see Check the video aspect ratio).

Notes

▪If the Grab Background Image window shows a white background, that may be due to the graphics card settings. See Troubleshooting > The camera image is not shown in the Arena Settings or Integrated Visualization

▪You can define and update a background of existing Arena Settings at any time, as long as they are not read-only. To do so, click the Grab Background Image button in the lower part of the Arena Settings window.

▪For all experiments from video: The default video file shown in the Video window is the last video used to grab a background image.

▪For DanioVision experiments: After grabbing the background image, EthoVision XT attempts to detect the well plates and draw the arenas automatically. Check that the outline of the arenas overlap with the well borders. If they do, click Yes in the window that appears. For more information, see the DanioVision DVOC-0041 - Reference Manual, which you can open from the Apps screen under Noldus > EthoVision XT 19 Other Documentation.

▪When presence of the animal makes it difficult to draw the arena, and it is not possible to grab a background image without the animal, do the following:

Open the Detection Settings. When the animal moves around in the arena, under Method click Background and use the Learn function. This saves a bitmap of the empty arena.

Next, In the Arena Settings, click the Grab Background Image button, then Browse and open the Bitmap Files folder within your experiment folder. From the file type list, select All files (*.*) to also view image files.

Choose the bitmap image just saved - its name starts with DetProf_. Next, click Grab.