Some persistently seem to believe it (e.g. Brock) but the evidence is not there in the optical properties.
The N version of the glass (e.g. N-BK7) are those without lead and arsenic and have the same optical properties of the glass they replace.
http://refractiveindex.info/?group=SCHOTT&material=N-BK7
http://refractiveindex.info/?group=SCHOTT&material=BK7
Of course if you find someone who believes that there is a difference then you should ask more for the bins.
Kevin,
Thanks for posting that information, but where is the "evidence" that all lead free glass used in binoculars since sports optics manufacturers switched over to lead free glass is of the N-BK7 type?
When manufacturers switched over to lead free glass, they didn't have an international standard in effect that said, you will add so many mols of Barium carbonate such that all lead free glass will have the same optical qualities and conform to ISO 9000 standards.
Either that or you are saying that all glass comes from Schott?
If you want to become a "believer," carefully compare a 10x42 LX with a 10x42 LX L, and you will "see the light," brother. In fact, more false color fringed light with the LX L and too much light on brightly lit objects.
Or compare a Leica 8x32 Trinovid BA with a Leica 8x32 Ultravid BR.
Or a 501 8x32 SE with an 8x30 EII (more subtle but still "evident").
I didn't have any preconceived notions before comparing lead glass bins with lead free bins, but after I did, the difference in CA was "clear".
Then I began reading about other "believers" who made the same observations:
http://www.birdphotography.org/show.php?threadid=57189
Then I began to collect "evidence" that supported my observations, but I lost those links when my computer died; however, I did find the study about lead free glass in microscopes.
Here's an excerpt, followed by a link to the article:
"Even if lead-free glass material with an equivalent refractive index and Abbe’s number is
developed, it is impossible to achieve the desired Apochromat performance especially for
highest-grade objective lenses with a high aperture number when the anomalous dispersion
degrades."
http://74.125.93.132/search?q=cache:k3kcQ3sWclQJ:www.jbce.org/files/6_No_13-2_Lead_in_Optical_Glass.pdf+lead+substitutes+in+lead+free+optical+glass&cd=1&hl=en&ct=clnk&gl=us
I do not have the technical expertise to trade equations or letter/number glass designations, but you are right in saying that I do "believe" what my eyes tell me about the differences in CA between lead free glass vs. lead glass.
If all lead free glass was just as good as lead glass, as you seem to suggest, I don't think we would be seeing an increase in use of ED glass in lead free glass roofs, but rather I think this trend is testimony that other "believers" have made the same observations (and complaints) about increased CA in their lead free roofs.
Hallelujah! I
do believe!
Can I have an Amen friends?