Josef Petzval, inventor of the first lens for portraiture, said that taking a photograph was not an optimal test of a lens because:

“anyone wishing to test a camera obscura lens by taking photographs with it commits the error of attempting to evaluate, simultaneously and all at once, the combined influences of the lens, the quality of the chemicals, the photographer’s skill, the weather conditions, the quality of the setup, the design of the camera, and so forth; the inevitable result is that, in the end, one cannot determine which aspect of the resulting effect is to be attributed to one or another of these many different causes.”

Petzval. J., Über das neue Landschafts als Fernrohr- Objectiv, (1858) (On the New Landscape Lens as a Telescope Objective)