It is possible to have a video size larger than the capture size, but this isn't recommended. It will increase the amount of data Guncam has to process without increasing the quality of the pictures.
This is used to tell Guncam where the upper left hand corner of the capture window should be placed. If "Center capture area" is checked (which is the default setting), Guncam will center the capture window. Moving the capture window is usually only useful for capturing 'windowed' games that don't take up the whole screen and are not centered.
Determining the correct coordinate for the top and left of the window can be difficult. It is recommended that one uses the "Use mouse to define Video Size, Capture Size, and Capture Position" option to determine these coordinates.
Use mouse to define Video Size, Capture Size, and Capture Position
This option allows one to determine the video size, capture size and position with the mouse. To use this option, click this button and then click down on the mouse button and drag the cursor. A box should appear on screen. This box represents the size of the video and capture area. When the box is the desired size, release the mouse button. Note: if "Capture Full Screen" is checked, this button will automatically uncheck it.
If the checkbox in the 'Capture
Position' settings is checked, a message-box will appear asking if you want to
capture the selected area. If one selects "No" in this message-box,
Guncam will position the capture area to the center of the screen.