Novel trimethine hemioxonol dyes are provided in which the polymethine chain of the dye includes the 1, 2 and 3 carbon atoms of a 1-cyclohexen-3-ylidene nucleus, the 1-carbon atom of said 1-cyclohexen-3-ylidene nucleus having the nitrogen atom of a tertiary amino group attached thereto. Photographic emulsions and elements are also provided featuring the trimethine hemioxonol dyes of the invention as spectral sensitizers or as filter material.