NOVELTY - Cyanine-type compound (I) is new.    USE - New cyanine-type compound is used as light absorption agent for optical filter (claimed). Uses include but are not limited to liquid crystal display apparatus, optical recording material, dye-sensitized solar cell, photoelectrochemical cell, non-linear optical apparatus, electrochromic display, hologram, organic semiconductor, printing ink, light-emitting dye, and cosmetics.    ADVANTAGE - The optical filter using cyanine-type compound has excellent quality, light resistance, heat resistance, and moisture resistance.    DETAILED DESCRIPTION - Cyanine-type compound of formula (I) is new.    R1,R2=1-10C alkyl, 1-10C alkoxy, 6-30C aryl, 7-30C arylalkyl (all optionally substituted) or metallocene-type compound of formula (i), in which methylene group of alkyl, alkoxy or arylalkyl is optionally substituted by -O-, -S-, -CO-, -COO-, -OCO-, -SO2-, -NH-, -NR-, -CONH-, -NHCO-, -CONR-, -NRCO-, -N=CH- or -CH=CH-;    R=1-10C alkyl or 6-30C aryl;    Q=H2C=CH-C(-X)=CH- or coupling group of formula (ii);    An power q-=anion;    q=1 or 2;    p=coefficient capable of maintaining electric charge in neutral state;    Ra-Ri=H or 1-4C alkyl, in which methylene group of alkyl is optionally substituted by -O- or -CO-;    Z=direct bond or optionally substituted 1-8C alkylene, in which methylene group of alkylene is optionally substituted by -O-, -S-, -CO-, -COO-, -OCO-, -SO2-, -NH-, -CONH-, -NHCO-, -N=CH- or -CH=CH-;    M=iron, cobalt, nickel, titanium, copper, zinc, zirconium, chromium, molybdenum, osmium, manganese, tin, palladium, rhodium, platinum, iridium or ruthenium;    X=7-30C arylalkyl, 1-10C alkoxy, 1-10 alkyl (all optionally substituted), in which methylene group of arylalkyl, alkoxy and alkyl is optionally substituted by -O-, -S-, -CO-, -COO-, -OCO-, -SO2-, -NH-, -NR-, -CONH-, -NHCO-, -N=CH- or -CH=CH-;    ring A=five-membered or six-membered heterocyclic ring, metallocene structure or aromatic structure of formula (iii);    R3-R7=1-10C alkyl, 1-10C alkoxy, 6-30C aryl, 7-30C arylalkyl (all optionally substituted), H, hydroxy, cyano, halo or nitro, in which methylene group of alkyl and arylalkyl is optionally substituted by -O-, -S-, -CO-, -COO-, -OCO-, -SO2-, -NH-, -NR-, -CONH-, -NHCO-, -N=CH- or -CH=CH-;and    R3+R4,R4+R5,R5+R6,R6+R7=ring.    An INDEPENDENT CLAIM is included for optical filter, which comprises cyanine-type compound(s).