Update README.md

Author: samuelmcdermott

README.md

@@ -85,14 +85,15 @@ The `MicroscopeClient` object has a few basic methods.  If you created an instan
 |`microscope.grab_image()` | |A `[image_height x image_width x 3] uint8 array` | Gets the next image the camera sends in its MJPEG preview stream.|
 |`microscope.calibrate_xy()`| | | Untested.|
 |`microscope.autofocus()` | | | Runs the fast autofocus  routine. |
-|`microscope.record_video()`| `format` : video format (`h264` and `mjpeg` tested) (default: h264) <br/> `framerate` : video framerate (fps) (default: 30) <br/> `length` : length of video (seconds) (default: 1)<br/>`save locally` : Logical on whether to save video locally (default: true) <br/> `save_location`: The directory in which to save the video (filename is the timestamped one generated by the microscope) (default: current working directory) | The location (either locally or on the microscope) where the video has been saved| Records a video using the [video extension](https://gitlab.com/openflexure/microscope-extensions/openflexure-videoplugin)
+|`microscope.record_video(format, framerate, length, save_locally, save_location)`| `format`: video format (`h264` and `mjpeg` tested) (default: h264)<br/>`framerate`: video framerate (fps) (default: 30)<br/>`length`: length of video (seconds) (default: 1)<br/>`save_locally`: Logical on whether to save video locally (default: true) <br/>`save_location`: The directory in which to save the video (filename is the timestamped one generated by the microscope) (default: current working directory) | The location (either locally or on the microscope) where the video has been saved| Records a video using the [video extension](https://gitlab.com/openflexure/microscope-extensions/openflexure-videoplugin).|
+|`microscope.preview()` | | |Launches a preview window displaying a live video feed from the microscope.|
 
 
 ## Extensions
 
 To run methods provided by the microscope extensions, you can use the `extensions` `struct` to make `get` or `post` requests.  
 
-**However**, due to MATLAB struct limitation, you need to replace any `.` in your extension name to `_DOT_` and any `-` to `_DASH`. For example, the extension `org.openflexure.autofocus` should be written as `org_DOT_openflexure_DOT_autofocus`.
+**However**, due to MATLAB struct limitation, you need to replace any `.` in your extension name to `_DOT_` and any `-` to `_DASH_`. For example, the extension `org.openflexure.autofocus` should be written as `org_DOT_openflexure_DOT_autofocus`.
 
 For a post request, `data` can be a `struct`, `character vector`, `numeric`, `cell` etc. The full list of supported types for post requests is in the [MATLAB documentation](https://uk.mathworks.com/help/matlab/ref/webwrite.html#buocgv5-data), but they have not all been tested.