---
title: "Check volume coverage"
canonical: "https://help.vicon.com/space/Evoke18/397967998/Check%20volume%20coverage"
format: markdown
---
After you have positioned cameras and Pulsars in the volume, ensure that the cameras can see the whole of the volume.

1. Ensure your cameras are physically connected to the system.
2. Ensure your Evoke system hardware is switched on, and that Evoke is running.
3. In the **System** panel (by default located on the left of the Evoke window), click the **Vicon Cameras** section heading (or click a camera and press Ctrl+A) to select all the cameras or, for a large number of cameras, right-click and click the relevant **Select** option.
4. In the **Workspace** ensure that the **Cameras** view is selected.
5. Using the default lens settings on each camera, ensure that:
  - You can see Pulsar images from each connected camera.
  - Two or more cameras can see every point in the volume in which you intend to track motion.

If you have difficulty orienting yourself in the **Cameras** view, you can check the aim and field of view of a camera in real time by switching the camera into Video Preview Mode. This mode displays a video image from the optical sensor of Vicon cameras that offer this option (Valkyrie cameras support Video Preview Mode at higher frame rates than other supported cameras: see [Video Preview Mode frame rates](#)). All other camera views and parameters are inactive.

> ℹ️ **Note**   
> ℹ️ Video Preview mode is for system setup purposes only. You cannot use Video Preview mode when you are calibrating, auto masking, capturing, or reviewing data.

Note that, for effective use of Video Preview Mode, strobeless cameras (Vipers) need independent illumination at a wavelength of 850nm.

> Macro (scroll-pagebreak)


    **To use Video Preview mode:**


1. In the **Workspace**, select the **Cameras** view.
2. In the **System** panel, in the **Vicon Cameras** list, right-click a camera and select **Video** **Preview Mode > Video Preview Mode**.
  The camera view changes to Video Preview mode and the camera begins shipping video data.
  **Video Preview Active** is displayed in the menu bar:
  While all cameras are in Video Preview mode, previews can only be viewed in one camera at a time. If you selected multiple cameras, only the last camera in the selection displays a preview.
3. To turn off Video Preview mode:
  - In the menu bar, select the X next to **Video Preview Active**.
    or
  - In the **System** panel, right-click any camera in the list and select **Video Preview Mode** > **Exit Preview Mode**.

If the preview image is dark:

- In the **System** panel, display the Advanced properties > Macro (inline-media-image)

 and make sure that ** Enable Strobes **is selected.
- Use external lights to illuminate your volume.
- Open the aperture.  When you have finished checking the camera aim and field of view, be sure to set the aperture back to its original value.

> ✅ **Tip**: For Viper cameras, we recommend that you leave the camera at its factory setting, even if you are using Preview Mode.

#### Video Preview Mode frame rates

All supported cameras can use Video Preview mode but their performance is dependent on frame rate:

- Valkyrie VK16 and VK26 cameras support Video Preview mode from 30–900Hz. At frame rates above a Valkyrie camera's full frame rate (see **Compare Range** towards the bottom of the [Vicon Valkyrie web page](https://www.vicon.com/hardware/cameras/valkyrie/)), Video Preview mode uses windowing to display the same field of view as optical mode.
- Valkyrie VK8 cameras support Video Preview mode from 30–300Hz at a reduced resolution of <span style="color: #1d1c1d">3232 x 2176.</span>
- Vantage Vero and Viper cameras support Video Preview mode from 30–60Hz. At frame rates above this, an image may be displayed but this has not been tested. Vantage, Vero and Viper cameras do not use windowing in Video Preview mode.

> ✅ **Tip**: To optimize data quality and the camera's field of view, you are likely to iterate between checking the camera focus and its aim. This is particularly true for Valkyrie and Vero cameras; as you adjust the varifocal lens, you will need to both re-focus and re-aim.