Hello Lewis,
Thank you for the question. When AirPlay Mirroring, the quality should match your television’s resolution. You can check the resolution when using AirPlay in System Preferences:
- Choose Apple menu > System Preferences, then click Displays.
- Click Scaled, then select a resolution. Some apps may not fit entirely on the screen in some scaled resolutions. Using a scaled resolution may affect performance.
OS X Mavericks: Adjust your display resolution
http://support.apple.com/kb/PH14388
Additionally, you can match your desktop size to the resolution for the Apple TV:
Optimizing image quality
Resolution Matching modes
You can choose between two desktop resolution matching modes that let you select which display will have the best image. When AirPlay Mirroring is turned on, select a "Match Desktop Size" choice via the AirPlay Mirroring menu extra.
- Match Desktop Size To: Apple TV
AirPlay Mirroring changes the desktop resolution to best match your Apple TV, resulting in a 16:9 image that fills the HDTV screen. This setting often produces the sharpest image on the HDTV. Note: The aspect ratio and/or resolution of the built-in Mac display may change to accommodate the Apple TV.
- Match Desktop Size To: This Mac
AirPlay Mirroring scales the contents of the desktop to fit on the Apple TV, leaving the resolution of your Mac's display unchanged. Use this setting for the sharpest image on your Mac's display. Note: Depending on your Mac model, the resulting image may not fill the HDTV screen.
About AirPlay Mirroring in OS X
http://support.apple.com/kb/ht5404
Thank you for using Apple Support Communities.
Best,
Sheila M.