When Sony dsc-tx7c took pictures, the white background was grayish yellow. How can it be pure?

There are two reasons for this: first, a large area of white, the machine will revert to 18% medium gray, you need to increase exposure, just use exposure compensation, and add 1-2 files. Second, white balance is color cast. You should increase the exposure before you can see the effect. If it is still color cast, adjust the white balance. This is related to the color temperature of the lighting source you use. It has nothing to do with the macro.