In spite of its limited time duration, and the reduced scientific impact, the technique of composite photograph developed by Sir Francis Galton has had a fairly long history as a metaphor and term of comparison in the philosophy of language and semiotics (with ethical bearings). Two fundamental stages of this story refer to Charles S. Peirce and Ludwig Wittgenstein. The first one (who shared with Galton - and others - close scientific relations with Lady Welby) uses very often the metaphor of composite photograph as a tool to describe the iconic character of conscience. The point stated by Peirce is that: no single photographic shoot (i.e., the analogon of an individual percept) is comparable to the icon which is the basis of every perceptual judgment. The composite photograph is an icon - and hence is firstness - despite its being composite, because it is used as a firstness, in its vague and general character. Peirce also speaks of Ethic (see CP 5.173) as a composite photograph of the conscience of a community. The ethical attitude constitutes an interesting subject to define the relation between Peirce and Galton. Peirce share with Lady Welby a communitarian view, whereas Galton share with his biographer Karl Pearson a kind of social Darwinism (exemplified by his views on Eugenics). And yet, Peirce attacks Pearson and his "Grammar of Science" as "The Gospel of Greed", whereas he always commend Galton as a good scientist. This is probably due to the fact that Peirce sees Galton's technique as a transposition of the methods of correction of computing errors he was working on as a computer for the Geodetical Survey. In any case, it is clear that he uses the metaphor in a way which is diametrically opposite to the purposes for which Galton had developed the technique: Peirce is not interested in identifying the precise traits of a human type (eg the criminal), but on the contrary he wants to obtain a It is a vague and general image to eliminate individual characters (since irreducible individuality is a defect for him, and not an exceptional quality). As for Wittgenstein, despite his very little knowledge about Galton, we know that he personally experiments the technique on his family, and he reflects on composite photograph as a way to reason on fuzziness and probability. His ethical attitude is not reducible nor the Peirce's neither to Galton's one, but it is maybe closer to Galton in respect to their common penchant for individualism. In conclusion, we can say that the technique of composite photograph, as an idea and metaphor, develops a trajectory largely independent of goals and results (quite disappointing, as Galton himself admitted) for which it was discovered and developed. Its heuristic potential (i.e., its power as a sign) proves to be much more fruitful than its scientific impact.