For more information on high index lenses click on the links below. It is also more expensive than crown glass . You are also very limited on availability of lens styles. Here are the basic colors available. These are the most popular photochromic lenses that are used by the majority of people who order photochromic glass lenses.
Temperature does have an effect on the lenses.
Extreme heat for example above 90 F will not let the lenses darken as much. On the other hand at cold temperatures the lens will get extremely dark in a shorter period of time. This darkens less. These work well for people who want maximum clarity indoors with moderate darkening outdoors. This new photochromic lens material has a feature where it may be ground thinner than regular glass.