You don't need a green screen to use mmhmm, but using one can give you more options for controlling how you look on screen. 

Here is what you need to do to get started using a green screen with mmhmm and some tips to enhance your image quality on screen

In-App Setup

1. Camera > tick the box for “I have a green screen,” and choose the color that most closely represents your green or blue screen. Otherwise, you can also choose the chroma key picker color wheel to dial in the exact shade of your background.

In Windows beta, locate the color that most closely resembles your green screen and adjust the threshold. 

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2. Threshold allows you to dictate the sensitivity of green screen detection so it recognizes the darker and lighter areas. Using the threshold sliders, adjust the range of hues that match your background. Experiment with the upper and lower bounds until you have a crisp silhouette.

Lighting your foreground

The existing lighting in your room should be sufficient for mmhmm, but lighting your face with other sources of light can go a long way in improving the quality of your broadcast. 

Generally speaking, studio lighting concepts translate well to mmhmm. Here are some of those for you to consider for your own setup.

• Ideal studio lighting illuminates a subject with soft, diffuse lighting from multiple angles to eliminate hard shadows. 
• In a typical three-point lighting setup, the main source of light, or the key light, is set at an angle to one side of the subject. A second, softer light, called the fill light, is used on the other side of the subject to fill in the shadow caused by the key light. The larger the difference in light intensity between the key and fill light, the greater the shadow. 
• A third light is sometimes used to light the subject's hair and shoulders from behind. This enhances a subject's silhouette and can make them stand out from the backdrop/green screen even better.
• Fabrics are placed over the lights to diffuse the light. By increasing the surface area of the light source, the light is "softened," creating a more flattering lighting effect. To achieve this diffusion effect, studio lights are placed in soft boxes or bounced off silver-coated umbrellas or through white, translucent umbrellas. 

Even without professional studio equipment, these concepts can be used to combine the natural and artificial lighting in your environment to replicate these effects. Even something as simple as a desk lamp bounced off the cover of a book can be used to greatly enhance the lighting quality of your broadcast. 

My shoulders and hair have a green outline when I use a physical green screen, what should I do?

This is called green screen spill, and can be mitigated by tinkering with:

• Consistent, diffused bright light on yourself, more than the green screen itself
• Adjusting the chroma key (see In-App Setup)
• Adjusting the threshold while working with the lighting
• Using the Zoom slider (Camera > Zoom) to crop your image if you have a smaller frame to work with