Here's a question I've wondered about for a while. Somewhere in some old newsgroup, Bob Shell (remember him?) stated categorically that the old chrome-shutter Mamiya TLR lenses are somehow sharper than the later black-shutter lenses. Yeah, I know this is counterintuitive. Apparently, he says, the chrome lenses were made to a 'commercial formula', and they made very stark unflattering portraits. In response to bleats from wedding and portrait photogs, who were primary users of the Mamiya TLRs, the Mamiya Corporation subtly altered the optics of the black series lenses, even though the lens formulas remained the same (for example, the 105 and the 135 were tessars, and so on.) Or so the story goes. So here's my question: what's the 'commercial formula' he's talking about, and what makes it different from any other lens? Is it corrected for more resolution? For more contrast? Does it just have more stringent quality control? Did Mamiya actually degrade the optics of the black lenses when they abandoned the chrome 'commercial formula'? To state it differently, what makes a 'Commercial Ektar' any different from any other tessar?