The white and black in color picture are not only the important color in frame, but they make the picture color appear to be pure and dense. Color scientists believe that nothing is absolute black or absolute white in the world. No matter how white get to be lighter or black get to be darker, it may also be accompanied with some color trend which can appear exaggerat white or black on the frame.Therefore when we duplicate , we should pay attention to the black and white tone in color picture, as is the important thing that raises image artistic effect.

　Nowadays, the most operating people only pay attention to the adjustment for color but overlook the handling of dark or white.Thus we frequently handle white object into a white area,as lose the level quality sense of white object completely as is similar to the black.There is several solution to solve this problem.

　1. Deepen the acknowledge for the importance of the white and black tune in color picture

　As we know,the visual effect of black and white photograph is more intense than the color photograph because the reflection contrast of black and white is much obvious than any other color group. According to scientist measurement,the contrast between color even as the most intense primary color or complementary color is more weaker than the contrast of black and white.For instance,the contrat of color group of green and red reach the 40% of group of white and black,the contrat of color group of blue and red reach the 23% and the contrat of color group of green and blue only reach the 19%,as is why black and white works sometimes are more sprightly than color works.Thus when we scan the white and black of the color picture,we will not only show the level and texture vividly but also emphasize the contrast of visual light and dark.

　2. The main points of handling white object

　White is called as extreme color in color studies, handling the white in color picture not only show the texture characteristic of various white objects but also make the light marked excellently. (1)Various white objects in color photography picture is influenced by the color of light source.Its color tone changes richly so we need to understand texture characteristic of various white objects which we must base on.Such as white paper, white cloud, white flower, white silk, white jade, white porcelain etc. We shoud adjust accordingly by the difference of texture characteristic.The white of white paper may be handled gently .The white of white jade and white porcelain will show the tactile impression of jade and porcelain.Some single color porcelain'surface is smooth and bright such as cyan shadows, day cyan and white glaze,as we should reappear the tactile impression.When we set the scan,we should keep the cyan-gray level of highlight portion.However,some picture book with porcelain image is printed to be large white area like white paper because the light tone has only 3%-5% of C plate meanwhile M plate and Y plate has no screen tone even some C plate is the same like those,as lose the tactile impression absolutely.

(2) The white of art picture has special characteristic.For example, the white of oil painting and opaque watercolour painting each is used pigment to cover other color to show itself.It's so white and textural.Thus we use the three primary color to mix to neutral white that we make the part extreme light have no screen tone. The white of watercolor painting embodies its white by putting apart watercolor white itself.Each watercolor painting has no less than one place to be pure white,as can let the printing beautiful and clear. So we could make the part extreme light have no screen tone when we set it.

(3)The white object of a lot of current printings appear color cast and color missing because of some operating people lack of grey balance consciousness. We should make the high light white objects set by percent dot area of grey balance such as C5%-6%, M3%-4% and Y3%-4%.If white is warm,the percent dot area of process color blocks could be close , but there is no one to be lacked.Otherwise the printings will appear color cast