So,
1.67 comes in two flavors. MR7 and MR10. MR7 is softer and is tintable, but still needs a backside coat applied. These can only be tinted prior to the BS coat. Once coated, however, the tint is locked in place and cannot be adjusted after the fact. I will not touch custom tints on full sized surfaced blanks, especially Grads, for obvious reasons.

So, overall, yes, tint-ability is based on the coatings used. Tintable coatings are softer and lower on the Bayer scale. 2.5-3.5 is the average. Not much better than an uncoated lens, IMO. 10 is the rating for glass. Best bet is to forgo custom tints, unless you stay with CR39. For other materials, stick with Polarized or Photochroms.

Poly actually comes in a variety of pre-tinted options. Brn3, Grey3, G-15(ish), Gradient and solid Polarized. A good alternative, and repeatable, if only one lens needs to be replaced at a later date.

A time consuming and more expensive option is to have a vacuum deposited tint, but your color options will be limited by the thin film provider.

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