def combine_exif(exif_data, lut, d):
    """
    Add extracted exif information to master list of HP data
    :param exif_data: dictionary of data extracted from an image
    :param lut: LUT to translate exiftool output to fields
    :param fields: master dictionary of HP data
    :return: fields - a dictionary with updated exif information
    """
    for k in lut:
        if k in exif_data and exif_data[k] != '-':
            d[lut[k]] = exif_data[k]
    return d