When doing work in Photoshop you need to keep in mind that what mode you’ll need to work in if you’re doing work for the web, TV, computer programs like gaming or for print in magazines and other publications. Additive colors refer to RGB color mode or primary colors of red, green, and blue and are primarily used for web and computer based input. Subtractive colors refer to the CMYK or complementary or secondary colors of cyan, magenta, yellow, and black. In subtractive colors the light hits the surface of the print sources, like photographs and images seen in magazines, the light is absorbed or subtracted and the rest is reflected. When you combine all three RGB colors you get white light and combing CMYK will produce black.
Colors is available everywhere you look. Research had reveal that there at least 16 million different colors in the spectrum. To know how light colors combine to create different colors we have to understand how much additive and subtractive colors are combined together in either equal or unequal amounts. When you combine two additive colors together, like Red + Blue you get Magenta and so on. Combining all three of the colors Red+Green+Blue you get white light. By changing the brightness of these colors you get a wide vary of colors. When you take RGB additive colors in unequal amounts and combined them you can get those vary of colors. For example, if you take 1 Red + 2 Green you get a Lime green color. In the case of subtractive colors, combining is different from that of the additive color which relies on light. Subtractive colors use pigment or dye. The mixing occurs when the light hits the surface and filtered through a transparent object. When paint mixing in CMYK two colors are combined one color absorbs and then creates the desired color. For example, blue + green, absorbs red and creates cyan.
The differences that affect the designer working in images for press is that the more process ink you add the more darker the images will become. Black is added for the sharpness of the print. Some colors may not be represent in the CMYK inks. Process color is the standard for printing presses. CMYK is limited in its color range but presses can produce their own greens and oranges to compensate since CMYK doesn’t produce very well. In process color its less about gamut, a set of colors and more about print mechanics. The key to best reproduction is to make sure your attributes in your file are set up to make accommodation for differences. As with the file sizes the recommended size is 300dpi or greater. The differences that impact the designer working in screen images is that the more light you add the lighter the color becomes. RGB has the broadest color gamut meaning each variation of color has a set different possible colors in a color system. A gamut is a subset of colors and that depends on its brightness. Computers allow 256 colors in their system. Monitors of today display about million colors. Web safe colors on the other hand require a reduction in file size. (Sheridan Press)
It is important that each image merge together in one composition have the same resolution depends on the size and the viewing distance of the image. In Photoshop when resizing images to match the background resolution it goes through an algorithm process. What is does it averages out the color and brightness with a mixture of tones and colors in the entire composition. When doing this process you access the image size from the Image menu, then select resample image, then change the resolution to its desired pixel size. What Photoshop does it spreads out or scrunches the image pixels. (AWD) As a result the pixels get bigger. So when making an image larger the pixels need to spread apart and if you shrink an image Photoshop needs to decide which pixels to remove. Photoshop was designed for both print and web, so it can handle the options of in changing pixel and print dimensions. But be careful about increasing and decreasing too much as you will lose clarity in your composition.
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The Sheridan Press. Color Space Fundamentals. Digital Expert. Web. retrieved 13 April 2011. http://dx.sheridan.com/advisor/cmyk_color.html
What is Color? RGB World, Inc. Web. retrieved 13 April 2011. http://www.rgbworld.com/color.php
Chastain, Sue. Increasing Image Resolution. Graphics Software About.com. Web. retrieved 13 April 2011. http://graphicssoft.about.com/cs/resolution/a/increasingres.htm
Photoshop Image Size and Resolution. AWD San Francisco. Web. retrieved 13 April 2011. http://www.awdsf.com/courseware/photoshop/ps2_ImageSize_Resolution.htm