This thread picks up from discussion in the two Caslon threads. I started a new thread because I don't want to talk about Caslon, and because I figured it would be easier to keep track of just how long it takes for Hrant and Gerald G. to get into a pissing match
A couple of observations on 'optical scaling':
Firstly, I don't think it is a very good term, although better than the common 'optical sizes'. What we're talking about is different fonts, which was obvious in the days of metal type, but ceased to be obvious with the advent of phototype, when any font could be scaled to any size (within the limits of the particular typesetting technology). Adobe's Multiple Master and similar interpolation or extrapolation technologies confuse things further, by offering the possibility of manipulating outlines in a single font at the same time as scaling. Now, with the demise of MM fonts, we're back where we were, and where I think we should be: optical scaling means different fonts.
Secondly, the value of interpolation -- which is still a useful tool in font making, even though it has, at least for now, disappeared from font formats -- is very limited in making fonts that are optimised for reading at different sizes. At the Linotype Typotechnica conference in Heidelberg, last February, I met Karl-Christian Lege from K