Profile shape and blackpoint relation

Created a profile that ended up with what appears, after checking the profile out via ColorThink, to have two blackpoints; i.e. two “spikes” at the black end of the profile.

Any insight into what is going on here?
What misstep did I take?

I used to see that alot, particularly with photo paper printer profiles made with ProfileMakerPro. You’ll see that when a device’s black point has a color cast. Essentially, one spike represents the DMax and the other spike represents its color cast. A lot of photo paper printer’s calibration processes prioritize DMax over neutrality, so they are particularly susceptible to this. PMP utilizes what you might call a relative black point and doesn’t attempt to neutralize the blacks; a working space R=0 G=0 B=0 stays a 0,0,0 in the destination space. Other profiling packages might produce a 11,0,11 black to eliminate a green color cast for example.

Some of my clients have dozens of photo paper printers under one roof so getting them all to match (particularly in the deep shadows) requires going beyond PMP’s profiling technology and entering more risky territory that can produce some great results if you have the patience to weed trough some headaches along the way.

Scott Martin