The “Full Screen" check box in the connect dialog controls whether the VNC session will be run in full-screen mode, taking up your entire screen. You can access options in full-screen mode by moving your mouse to the top of the screen. A hidden toolbar with options to disconnect or leave full-screen mode will appear.
The “View Only" check box controls whether you’ll have control over the VNC server. By default, you can control the remote computer using your local mouse and keyboard while connected. If this check box is enabled, you can only view the remote desktop. Depending on the remote computer’s VNC server configuration, you may only be allowed to view the remote desktop.
The “Scaling" check box controls whether the image sent from the remote server is scaled to fit your screen. The “Keep Aspect Ratio" check box under it preserves the aspect ratio of the original image as long as it’s checked, preventing the remote desktop from looking stretched horizontally or vertically.
The “Use JPEG Compression" check box controls whether the image sent is compressed using the JPEG compression standard, used for images all over the Internet. Some VNC servers may not support this option.
The “Depth Color" drop-down box controls the color depth of the image sent from the remote desktop. It’s set to “User Server Settings" by default, preserving the colors and quality of the image seen on the remote desktop. Higher color depths require more bandwidth; try reducing this option if the session seems slow.