Archived posting to the Leica Users Group, 2009/10/08
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]> Frank Filippone wrote: > >> Makes no difference to the cost of the blanks. A chunk of glass of type >> ABC >> is the same, regardless of the grinding yet to be done on it. Yes, the >> cost >> of making those blanks into a finished lens element may/could/probably is >> different. > > Company A can specify glass type ABC with tolerances for refractive index > +-0.2% dispersion +-0.25% surface hardness +-0.3% expansion coefficient > +-0.7% > and company B can specify the same glass type with tolerances 1/2 of > company > A's requirements and I'll bet company B's glass blanks are gonna cost more > and > the finished lenses will show a lot less sample variation. > > Doug Herr > Birdman of Sacramento > http://www.wildlightphoto.com > > > And there's glass which isn't even glass. Fluoride whatever. Its also good for your teeth. And glass which is ground using sophisticated methods hence our ASPH's starting with the 24 2.8 made with the Schneider machine and other methods first by hand costing thousands. But then using molding methods which was ahead of its time but in the end perhaps did not work out. By Frank is right glass is glass they'd save money just taking the window panes out of the windows and using those. Mark William Rabiner