TAILIEUCHUNG - Photoshop Lab Color- P10

Photoshop Lab Color- P10: LAB has a reputation for enormous power, yet virtually all reference materials that advocate its use illustrate its capabilities with a single class of image. This chapter introduces the basic LAB correction method and explains why it is so extraordinarily effective. if you happen to have a picture of a canyon. | Figure The middle row holds the reference colors. Are the colors at the top closer to the middle ones than the bottom ones are A machine would think they are each equally far off. The Universal Interchange Standard 271 shot from a product of GretagMacbeth a leading vendor of color measurement instrumentation. It has measured 50L 30 A40B where the desired value is 50L 40 A30B and it wants to know how far different these two greens really are from one another. Notice first that below the color wheel on the left the program permits us to express these colors in xyY or even LUV if we d like to avoid LAB. But that s a side issue. The big action is underneath the green circle where we find one large and three small numbers that are introduced by the lowercase letter d. It stands for the Greek delta which mathematicians often use to denote the quantity of change. The asterisks remind us that the snooty name is L a b . In comparing the two colors the program notes that the L values are identical so dL 0. da and db are both 10. To Each His Dulcinea A knight errant who loses his lady Don Quijote remarked to Sancho is like one who loses the eyes that let him see or the sun that shines on him or the food that maintains him. I have told you this many times before and now I say it again a knight errant with out a lady is like a tree without leaves bricks without mortar and a shadow without the body that cast it. Right above the three readings we ve just been discussing in Figure much larger type informs us that dE . That s the key the iconic number. Pronounce it Delta-E and prostrate yourself before it if you believe that machines see color better than you do. Delta-E is an attempt to quantify the three readings on the line below it to create one comprehensive number that describes how far the two colors are from one another. There are several formulas to produce it this one involves weighting the A channel more than the B a lot of square roots and other fancy .

Đã phát hiện trình chặn quảng cáo AdBlock
Trang web này phụ thuộc vào doanh thu từ số lần hiển thị quảng cáo để tồn tại. Vui lòng tắt trình chặn quảng cáo của bạn hoặc tạm dừng tính năng chặn quảng cáo cho trang web này.