def special_mode(v):
    """decode Olympus SpecialMode tag in MakerNote"""
    mode1 = {(0): 'Normal', (1): 'Unknown', (2): 'Fast', (3): 'Panorama'}
    mode2 = {(0): 'Non-panoramic', (1): 'Left to right', (2):
        'Right to left', (3): 'Bottom to top', (4): 'Top to bottom'}
    if not v or (v[0] not in mode1 or v[2] not in mode2):
        return v
    return '%s - sequence %d - %s' % (mode1[v[0]], v[1], mode2[v[2]])
