Formula for collectability?

While the appraisal skills say in the tool tip they give the collectability in function of perception, most notably Methodical appraisal claiming to give x1, it doesn't actually give the actual amount of perception score. Has someone figured out the actual formula of how much collectability is given for certain perception score, as well as, is it linear?

http://home.eyesonff.com/showthread....ectables-Guide

Try this. :)

I was just about to ask this, either the tooltips are extremely inaccurate or or the skills aren't working right. 110 is definitely not .8x of 450.