Ferrotypes and ambrotypes are also usually developed with a developer that heightens the reflectivity, I believe. I'm sure you could do the same with sheet film with a high silver content if you wanted.
Well, that is the whole basis for my original post. Is it the developer alone that contributes to the images tone, or is it the collodion emulsion + special developer that makes the image reflect more light? Is it just the Iron developer? If so, cannot one use this developer on modern film and get the same result?