Every photographer who has ever fussed with an f-stop dial is unknowingly following advice that was already considered textbook knowledge in 1880. William Heighway's Hand-book of Photographic Terms — a pocket reference for the working photographer of the late Victorian era — opens with an entry on aberration that explains, in plain language, the optical problem every modern lens designer still wrestles with.

Heighway describes spherical aberration like this:

"the deviation of the rays of light from the true focus of a curved lens, in consequence of which they do not unite in a single point (the marginal rays having a shorter focus than the central rays), but are spread over on a small surface and form a somewhat confused image of the object... This is exhibited in the photographic camera by the impossibility of getting sharpness over the whole field of the ground glass. The centre of the picture being in focus, the marginal rays will form a circle of diffusion which gives a blurred appearance to the picture."

Then comes the practical fix, stated almost in passing:

"The fault is lessened by using diaphragms or 'stops' q.v., and by lengthening the focus."

That single sentence is the physical justification for the entire f-stop system that survives, essentially unchanged, on every camera lens manufactured today. When you stop your aperture down from f/2 to f/8, you are doing exactly what Heighway recommended: clipping off the marginal rays — the misbehaving ones at the edge of the lens — and letting only the well-focused central rays pass. The center of the picture stays sharp; the edges become sharp too.

For chromatic aberration, Heighway gives the other still-current solution:

"This fault is avoided by combining substances of different refractive powers, as, for example, crown and flint glass in the same lens."

This is the achromatic doublet — invented by Chester Moore Hall in 1733 and still found in every camera lens, telescope, and pair of binoculars in use today. The Sony, Canon, and Nikon lenses sitting in modern camera bags are direct descendants of this 18th-century trick, refined but not replaced.

What's quietly remarkable is how completely this knowledge has been black-boxed for modern users. A photographer in 1880 knew why stopping down sharpened the image — it was the first definition in their reference book. A photographer in 2026 typically knows only the rule of thumb ("f/8 and be there"), with the optical reasoning offloaded entirely to lens engineers.

The Victorians weren't ahead of their time here; they were simply at their time, with a working understanding of the physics they used daily. We've gained better glass and computational corrections, but we've also lost the casual fluency with which a 19th-century jobbing photographer could explain why his picture was sharp.