" I have read, " says Sir J. F. W. Herschel," with considerable interest the remarks of Sir W. J. Newton, On Photography in its Artistic view, etc., communicated to the Photographic Society, and by them printed in the Journal of their Society (No. 1). These remarks are in perfect consonance with my own impressions as to the absence, in the very best photographic landscape I have seen, of a true artistic representation of the relative intensities of light and shade, the consequence of which is usually a most painful want of keeping ;—a struggle to come forward of parts which nature suppresses, and a want of working out, in features which, to the eye, are palpably distinct.
" Sir W. J. Newton strikes with the true eye of the painter on the more prominent evil of the whole case ; he says (p. 6), ' Wonderful as the powers of the camera are, we have not yet attained that degree of perfection as to represent faithfully the effect of colours, and consequently of light and shade. For instance, a bright red or yellow, which would act as a light in nature, is always represented as a dark in the camera, and the same with green. Blue, on the contrary, is always lighter. Hence the impossibility of representing the true effect of nature, or of a picture, by means of photography.'
" No one can have viewed the exquisite pictures of M. Reg-naidt or Mr. Stewart, without feeling that vegetation is unduly black and wanting in artistic production. No one who has studied colours, not as an artist, but as a photologist, can for a moment be ignorant of its cause. The red and yellow rays, and especially the former, which form so large a portion of vegetable greens, are suppressed. They affect not the materials at present used in the photographic art in its highest development.
" One word suffices for the key of the difficulty—Iodine. It is to the practically exclusive use of this element that the whole evil complained of (most justly) is attributable. I have shown (see my papers, Phil. Trans. 1840, 1842, Articles 129, 217, and ' On the Action of the Rays of the Solar Spectrum on the Daguerreotype plate,' Lond. Ed. and Dubl. Phil. Journal, 1843, Art. xix.) that iodized silver is insensible, or nearly so, to the red and orange rays—that its range of sensibility begins, with astonishing abruptness, beyond the medium yellow and within the blue region—is powerful at the indigo, and extends far into rays which have absolutely no effect in producing vision. No wonder then that iodine produces pictures unsatisfactory to the artistic eye. Iodine then must be thrown overboard or limited in its use, coute qui coute (and the sacrifice is a formidable one), if photography shall ever satisfy the desires of the artists.
" What then are we to have recourse to ? Bromine. A new photography has to be created, of which bromine is the basis. This I have proved in my experiments on this substance (Phil. Trans. 1840, Art. 77 ; also Art. xix. Lond. Ed. etc. Journal, above cited). The action of every luminous ray, so far as can be traced, is equable throughout the spectrum ; but the rays beyond the luminous ones act powerfully, and these must be eliminated. A glass screen, with a very slight yellow tinge applied close to the focal picture, or, still better, a glass cell, with optically true surfaces, containing a weak solution of sulphate of quinine, according to the recent results of Prof. Stokes, will effectually cut off these, and reduce the action of the rays within the limits which art recognizes. I believe M. Becquerel has used the latter liquid with a similar view. I will only add, that it were much to be wished that artists would study the spectrum and its habitudes in relation to their pigments".