photoshop curves

www.earthboundlight.com/phototips/photoshop-curves.html
www.cambridgeincolour.com/tutorials/photoshop-curves.htm
www.thegoldenmean.com/technique/curves1.html
www.zuberphotographics.com/content/photoshop/curves
www.znanje.org/knjige/computer/photoshop/03/podesavanje%20boja/ostala%20podesavanja/ostala%20podesavanja.htm