RGB CMYK and Grayscale are all acceptable. Halftones should be high contrast with sharp detail because some loss of detail and contrast is inevitable in the production process. Good contrast is particularly important for chromatographs. Each file must be no larger than 10 MB; figures should be 10-20 cm in width and 1-25 cm in height. Graph axes must be exactly perpendicular and all lines of equal density (.5 point minimum).