New components and chemistry involved within the newest generations in the lenses have produced substantial progress in addressing the two basic standards for choice :
Older generations (and some current generations) keep a yellow or slightly jaundiced hue even if not uncovered to ultra violet light-weight (indoors as an example). The latest generation Transitions are extensively regarded to become the top obtainable and practically fully clear within the absence of extremely violet.
Most newer photochromatic lenses create a speedy changeover from light to darkish as they may be uncovered to extremely violet - the true test along with the differentiation will be the price at which they regress in the darkest tint to distinct. Again Transitions lenses are widely thought to be greatest in school within this regard.
Transitions lenses are a broadly held trademark for a particular (newest) era of supplies and technology which are mixed and offered beneath the "Transitions" manufacturer. Other (but equivalent) names aren't the same, and are generally regarded to become not as great, as they are from more mature technology photochromatic technology.
Finally - never count on your photochromatic lenses (regardless of which model or technologies) to make considerably of a distinction whilst driving, because the windscreen of a auto is developed to absorb the majority of the UV prior to it enters the cabin - hence the lenses within your eyeglasses have absolutely nothing to respond with. In the event you need to have or would like tinted lenses while driving, you might be far better off obtaining two pairs from the exact same frame with prescription obvious and prescription tinted lenses.