So get this, my ref/zapplink image I found on google image that I used for my anatomy study was a freaking 3D render of this guys work. IT's a TRAP!! Hurray for Study's of Studys...:( http://www.zbrushcentral.com/showthread.php?t=57740
Well, darkest parts of background plate are lighter than black border on both images. If it's slight difference you're going for then I'd say right image has correct contrast :) Btw, have you tried "auto contrast" in photoshop? Sometimes it produces bizzare results but it's often useful.