> For the complete documentation index, see [llms.txt](https://docs.hello-robot.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.hello-robot.com/stretch4_docs/working-with-stretch/sensor_basics/accessing-the-cameras.md).
# Accessing the Cameras
Stretch 4 has four cameras in total. Three cameras are in the head, and one stereo-pair in the gripper.
This document will cover:
* [Cameras Overview](#cameras-overview)
* [Head cameras](#head-cameras)
* [Gripper camera](#gripper-camera)
* [Visualizing the cameras with ROS2](#visualizing-the-cameras-with-ros2)
* [Using the cameras in your code with ROS2](#using-the-cameras-in-your-code-with-ros2)
* [Visualizing the cameras with Python](#visualizing-the-cameras-with-python)
* [Using the cameras in your code with python](#using-the-cameras-in-your-code-with-python)
## Cameras Overview
### Head Cameras
The two peripheral fisheye cameras named Left and Right, denoting their mount location relative to the robot's right and left, provide a wide field-of-view 1920x1200 resolution imagery at 30fps for seeing around the robot without rotating the base. The fisheye cameras can see up to 5ft behind Stretch 4, and all around the side and front of the robot.
The Center high-resolution 12MP camera is useful for reading small text or AI Object detection.
The Left and Right cameras can alternate to see below the arm. The center camera's view is susceptible to occlusion by the arm.
### Gripper Camera
A stereo camera is mounted on Stretch 4's wrist, prior to the tool attachment site, to allow you to view objects in the robot's gripper or in front of the active tool. You can access the left and right camera feeds individually, if desired.
## Visualizing The Cameras With ROS2
In your terminal, start these launch files:
Terminal 1:
```
ros2 launch stretch_core gripper_camera.launch.py use_rviz:=true
```
Terminal 2:
```
ros2 launch stretch_core luxonis.launch.py use_rviz:=true
```
The `use_rviz` parameter will start rviz2, with a live visualization of the cameras.
`luxonis.launch.py` and `gripper_camera.launch.py` are launch files that live on the robot at `~/ament_ws/src/stretch4_ros2/stretch_core/launch`. Previews of these files can be found [here](https://github.com/hello-robot/stretch4_ros2/blob/jazzy/stretch_core/launch/).
### Using The Cameras In Your Code With ROS2
The `luxonis.launch.py` launch file will publish three `image_raw` camera topics:
* `/cameras_head/left/image_raw`
* `/cameras_head/center/image_raw`
* `/cameras_head/right/image_raw`
The `gripper_camera.launch.py` launch file will publish two RGB camera topics, one stereo-depth camera topic, and one PointCloud2 stereo-depth topic:
* `/cameras_gripper/left/image_raw`
* `/cameras_gripper/center/image_raw`
* `/cameras_gripper/stereo/image_raw`
* `/cameras_gripper/stereo_left_rgbd/points`
You can subscribe to these topics in your ROS2 node to receive point cloud points.
## Visualizing The Cameras With Python
To access the cameras using python, use [`stretch4_body`](https://github.com/hello-robot/stretch4_body/blob/main/docs/primer_cameras.md).
In your terminal, launch:
```
stretch_camera_show --left_right_center --rerun
```
or
```
stretch_camera_show --gripper --rerun
```
This will start a [Rerun](https://rerun.io/) window with the rotated images from the cameras.
### Using The Cameras In Your Code With Python
`stretch4_body` offers a Stream API for accessing the camera streams using a python Generator:
```
from stretch4_body.subsystem.cameras import *
for image_frame in stream_left_camera():
if image_frame is None:
print("No frame returned")
continue
print(f"Got image: {image_frame.image.shape=}, {image_frame.timestamp=}")
```
For more information, check out the Cameras Primer docs:
---
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