Why didn anyone who posed for a portrait notice the lens and write about it?
To address a question like this I have to speculate rather than being able to rely on optical evidence. However, I can think of a number of plausible reasons, and readers of this FAQ no doubt will be able to think of additional ones. For example, the concave mirror we calculated that Lorenzo Lotto used to aid him in painting certain features on the table covering in ‘Husband and Wife’ was only ~2.4 cm (1″) in diameter. Thus, it would have been quite inconspicuous had anyone else even been in the studio at the time (there would have been no reason for anyone else to be there while he painted the table covering). The lower left photo on page 76 of Secret Knowledge shows the layout of a studio, with the mirror~4″ diameter in that caseon the partition just behind David’s head. Even with this larger mirror, and even without other items hanging from that partition, such a mirror clearly would not have been very noticeable or noteworthy even if the subject had been looking in its general dire
