From VFXPedia

A/B Buffers

Each display view has two buffers for viewing images. Each buffer can be considered a complete and separate view. Generally, all that is seen the default A buffer.

Note Buffers can be set to different display view types. It is entirely possible to have an A buffer showing the image with a B buffer showing a histogram.

Switching Between Buffers

Toolbar

Click on the view toolbar button labelled A or B to switch to the associated buffer.

Keyboard

Use the comma (,) key to set the active view to the A buffer, the period (.) key to set the view to the B buffer and the (/) key to enable the split wipe mode (described below).

Split Wipe Images

The A|B buffers can be used to enable a split display, where the separate buffers are displayed onscreen simultaneously. The displays are separated by a red splitter bar, which can be adjusted in any direction or angle by click-dragging on the splitter.

To enable the Split Wipe, click on the A|B button.

Turn off the split wipe mode by switching to either the A or B buffer directly using the toolbars or keyboard shortcuts.

While split wipe is enabled, new tools can still be dragged and dropped into either buffer to change the image displayed. Panning or zooming either buffer will keep the other buffer in sync.

Different channels, view LUTs or other display options can be selected for each buffer individually. This allows easy comparison of channels, LUTs etc while in split wipe mode, or by quickly switching between the A and B buffers with the hotkeys.

Occasionally, you will have either zoomed in or panned so far from the splitter that it will be no longer visible in the view. Holding down Ctrl+Alt and clicking anywhere in the image will cause the splitter to jump to the current mouse position.

Holding down Shift while dragging the splitter bar will "snap" it to the nearest 45 degree angle.