Originally posted by troyz The center MTF measurements I'm thinking of (see for example, the Pentax DA21 from photozone.de) aren't even close to 500 lp/mm you specify.
Well, the DA21 has excellent center resolution. But not a stellar one. What you can see by the fact that it has its best resolution at f/5.6, i.e., not even f/4.
A 500 lp/mm lens on a K10D as used by photozone.de, however, would measure at only about 1/(1/82.5 + 1/500)=70.6 lp/mm (or 2225 LW/PH). According to an old Kodak formula which I don't trust. But you get the idea. Any photozone figure very close to the sensor resolution (2592 LW/PH for the K10D) must indicate a lens with stellar performance (e.g., the 30mm Sigma is 95% close!). Another indicator is a lens with best resolution
below f/4. Because it means that already
below f/4, all abberations except diffraction have almost disappeared.
Both indicators (LW/PH close to sensor resolution, best resolution at low f) can be deduced from photozone. But their choice is limited and it looks like the best lenses from this choice are Zeiss and Canon 24/1.4L.
So, I am looking for more resolution databases to extend my search. Esp. to rangefinder or old glass.