Bc 1: M hnh gc ra (tt nhin ri )

Bc 2: Tm Black Point v White Point

Ta chn Adjustment Layer => Thershold

c mn hnh nh sau

Ko con trt hnh tam gic qua phi, mn hnh ti h. a con trt v tr nh trn hnh, ta s thy 1 s im mu

trng. l nhng vng c im m ta s nh ngha l im sng nht trn hnh.

Cch chn im nh du: gi nt Shift v click chut tri vo vng mu trng

Tng t cho bn tri tm im ti nht

Sau , ta chn Cancel ca Thershold, v nh du xong ri.

Tip n, ta dng Adjustment Layer Level chn Black Point v White Point cho hnh.

Dng white point picker (khung mu xanh) click vo im nh du White Point, tng t cho black point picker

(khung mu ) click vo im nh du Black Point.

Ta c hnh nh vy

Bc 3: Tm Gray Point

Ta to 1 layer mi, trng, nm ngay trn layer Background.

Chn Edit => Fill (hoc n Shift + F5)

Ta chn mc 50% Gray

c mt mn hnh xm xt . V ng tc RT QUAN TRNG l chuyn Blending Mode thnh Different

Ta c 1 tm hnh kinh d nh sau

ngha ca Blend Mode Different l n so snh nhng im khc nhau ca layer hin hnh vi layer nm di n v

th hin bng nhng mu (k qui) khc nhau nh vng, tm ... Tuy nhin, gia 2 layer ny vn c nhng im

tng t nhau v c th hin bng mu en. Nh vy, nhng im ging nhau ca 2 layer s bin thnh nhng

im ti nht trn hnh. chnh l nhng im Neutral Gray Point ( l: nhng im xm trung tnh, dng set

Gray Point trong Level).

Vy lm sao ta xc nh nhng im ny? Nh ni trn, trong Blend Mode Different, l nhng im ti

nht ca hnh, vy 1 ln na chng ta s dng cng c Threshold xc nh chng

Ko v bn tri, Shift + Left Click mark li Dark Point (Dark Point y chnh l Dark Point trong Blend Mode

Different; khi Blend Mode Normal, n chnh l Neutral Gray Point)

Sau , ta Cancel Threshold, delete lun layer c fill 50% gray. M li Adjustment Layer Level, ta dng Gray Point

Picker click v Gray Point nh du.

Ta c hnh nh sau

Bc 4: Tinh chnh

Em xi Photoshop CS3, cc bc m tab Info nm cnh tab Navigation v Histogram pha trn cng tay phi. Cc bc

s thy 3 vung thng s nh hnh di y.

Trong #1 chnh l White Point, #2 chnh l Black Point v #3 l Gray Point. Trong h mu RGB, khi R/G/B l

255/255/255, l pure white; 0/0/0 l pure black v 128/128/128 l neutral gray.

Nh vy, theo thng s hin thi, my im Black, White v Gray ta ang c cha chu pure. chnh cho n pure, ta

dng cng c Curve

Ta bit, #1 l White Point, #2 l Black Point, #3 l Gray Point, vy lm sao ta a nhng im ny ln ng Curve

tinh chnh? Ta thc hin iu ny bng cch m Adjustment Layer Curve ln, Ctrl + Left Click vo tng im, n s

hin ln ng Curve trong bng cng c

Sau khi xc nh c cc im cn chnh trn ng Curve, phi xc nh l ang Channel RGB, chn im v dng

phm di chuyn, n tng cht mt v xem cc thng s thay i.

Cc bc s thy, em chnh cho White Point v 245/245/245, Black Point v 10/10/11, Gray Point v

128/129/130.

Ti sao li k vy? trn em mi kiu l phi chnh 255/255/255 mi ra pure white v 0/0/0 mi ra pure black m gi

chi k vy? L do em chnh 245/245/245 v 10/10/10 chnh v em khng mun mt i cc chi tit vng sng v vng

ti ca hnh. Chnh nh vy th hnh s khng c tng phn cao nht, nhng ngc li gi c nhiu chi tit hn.

V mt iu phi gii thch thm v s khng ng nht v thng s ca 3 knh RGB tng im v chnh Channel

RGB n l chnh th, chc chn kh c th ng nht c. Ta s tinh chnh tng knh mu Red, Green hoc Blue

m bo thng s gia cc knh l ging nhau.

y ta thy Black Point c thng s R/G/B l 10/10/11, chng t knh Blue cn cha chun; vy ta chn Channel

l Blue, chn Black Point (Shift + Left Click vo Black Point mark trn hnh) ri chnh li thnh 10

Tng t cho Gray Point, cha chun knh Green, ta chnh li knh Green

Hnh gc

Hnh sau khi sa