When your focus is sharp at full zoom but soft when zoomed out, your back focus needs adjusting! The Back Focus Test Card, ‘Siemens Star’ will help you calibrate your equipment back to sharpness at full zoom and wide angle. This card can also be used as a standard focus card when videoing or shooting with focusing difficulties. This card is A4 (297mm x 210mm) in size and printed on a quality 350gms matt laminated art board.