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