Dyestuffs of the formula ##STR1## are provided wherein R.sub.1 is hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, amino or substituted amino, amido or substituted amido or hydroxyl, alkoxy, thioalkoxy or a carboxyl group or an ester thereof, R.sub.2 represents either --N.dbd. or a linking group .dbd.CH--(CH.dbd.CH).sub.n -where n is 0, 1 or 2 and R.sub.3 is an optionally substituted heteroaromatic ring which optionally may be benzannelated, an optionally substituted benzene ring, an optionally substituted 5- or 6-membered heterocyclic or carbocyclic ring, which contains at least one hydroxyl group and may optionally be benzannelated, or R.sub.3 is a group ##STR2## wherein n is 0, 1 or 2, V is an optionally substituted 5- or 6- membered heterocyclic or carbocyclic ring, and Q is a group of the formula ##STR3## where each of W and Y are hydrogen, optionally substituted alkyl, optionally substituted cycloalkyl or optionally substituted aryl or together they represent the atoms necessary to complete a 5- or 6 -membered ring system, and X is an anion.The dyestuffs of the present invention are of use as dyes in photosensitive material which are not required to be present in the exposed and processed material. The dyestuffs of the present invention thus are useful as antihalation dyes, filter dyes and as acutance dyes.