Was this a thing? Did photographers in the 1890s charge people extra for large heads? Why?

"Large head" ("grosse tête" in French!) was 19th-early 20th century photography lingo for what we call today a "head shot", ie a close-up portrait where the face of the subject occupies most of the surface of the image. The term was already used for painting and drawing, but it seems to have turned into its own genre in photography in the mid-19th century. A artist who specialized in expressive, beautiful "large heads" was the British photographer Julia Margaret Cameron (Sir Henry Taylor, 1867).

There were two ways to obtain "large heads": "enlargement" (the subject's body was photographed and only the head was kept after enlargement) or "direct" (only the head was photographed). Photography magazines ran lively discussions about the pros and cons of each method. In the British Journal of Photography (20 February 1874), H. Garrett Cocking argued that direct large heads were better for tone and natural, lifelike expression, even though the lens used were more expensive. However, direct large heads sometimes lacked sharpness. Children had trouble sitting for direct shots, so enlargement was preferable for them. In the same journal, R.W. Aldridge noted issues with large lenses used for direct large heads, such as distortions (due to short focus) and lengthy sitting times, though he also agreed that direct pictures had "more force, depth, and brilliancy, more detail, and I believe, more refinement". In the American Journal of Photography (October 1889), Thomas R. Dallmeyer argued that direct large heads were generally better and more pleasing than enlargement ones, provided that the photographer used long focus lenses.

And there was another problem with large head portraits: at a time where retouching was common (and Photoshop did not exist), these portraits took longer to "fix", as explained by Fritz Eilender in The Photographic Times (6 July 1894):

Besides all the requirements for a good photographic portrait, a certain amount of hand work is absolutely necessary, especially with direct large heads. One of the main tasks of the retoucher is the preservation of the general face character ; all details should be seen in the finished picture, without deep and black shadows, and without, in comparison with them, chalky lights. Light draperies, and the highly illuminated parts of the face, show details, or gradations of tone, in a well-developed negative, and must remain so. [...] Wrinkles, deep lines, the pores of the skin, and accidental faults may be softened, so as not to interfere with the general effect, to do which, light and shade must remain well balanced.

"Large heads" were a popular type of portrait, but they were also more technical and more resource-intensive, which may explain the application (or not) of extra charges by the photographer.