The Screen capture check box tells VisIt to grab the image directly off of the computer screen. This means that the saved image will be exactly the same size as the image on the screen. There are advantages and disadvantages to using screen capture. An advantage is that capturing the image from the screen does not require VisIt to redraw the image to an internal buffer before saving, which usually results in a faster save. A disadvantage of screen capture is that any other windows on top of VisIt's visualization window occlude portions of the image. Screen capture can also be very slow over a sluggish network connection. Finally, using screen capture might not provide images that have enough resolution. Weigh the advantages and disadvantages of using screen capture for your own situation. Screen capture is on by default.