Click on the Use view mode button to select the view mode, or press the Q key when the image is in focus.

There are 2 sub-modes in the view mode.  Press the Q key when you are in this mode to switch between the sub-modes.

View images/frames

Use this mode to browse through the series of frames/images using the mouse wheel.  You can also hold down the left mouse button and move the mouse up/down to browse the images/frames.

Press CONTROL and scroll the mouse wheel to zoom in and out of the current image.

View current image

Use this mode to change your view of the current image.  Scroll the mouse wheel to zoom in/out of the image.  Hold down the mouse button and move the mouse to pan around the image when it is larger than the displayed area.