-----Quality control is not a job, it’s a attitude. And it starts with the understanding that a chain is only as strong as its weakest link. In the production relay race, the attitude of no compromise must prevail.
-----THE BASICS. There are three major building blocks to image quality control: Bit Depth, Resolution, and Gamut. If an image is to be printed accurately it must maintain certain critical standards. You cannot achieve excellence with inferior materials, so too, each image must possess certain minimum qualities.
-----Let’s begin with Bit Depth. This is basically how many shades of each color (Red, Green, and Blue) comprise the image. An 8-bit image provides 256 levels of color from solid color to white. Three colors providing 256 colors each equals over 16 million color possibilities by which an image can be expressed. While that sounds like a lot of colors, consider that the average digital camera can capture 10-bits (over one billion colors). Enough? Some think not.
Next, Resolution. In digital photography, resolution determines size. Resolution is expressed in pixels, or picture elements. ----These pixels are arranged as a grid like a checkerboard. Pixels look like tiny squares filled with color, and in this country are measured by the inch. The computer screen has a resolution between 72 and 96 pixels in each linear inch (measured horizontally and vertically). But the printing press uses a grid of dots that vary in size from 85 to as many as 200 (and more), and are measured diagonally- on a 45° angle.
----How the pixels of varied shades of are transposed into printing (halftone) dots is a rather complicated process and involves some serious calculations.
----An image captured with too little resolution for the reproduction size desired will produce blurry or pixelated results. Depending on lpi (line screen, or “frequency” if you’re geeky), an image should contain one-and- one-half as many pixels per inch (ppi) as it will contain halftone dots at its reproduction size.-----Once again, too few pixels per inch will produce a blurry picture, but too many
pixels only serve to bog the transposition process down and can actually tend to soften the detail of an image.
-----Finally, Gamut. An image’s gamut is determined by the RGB color mode chosen. RGB is not a definition of color, it is a class of Red, Green, and Blue colors. There are many different models of RGB... sRGB, Adobe RGB (1998), Apple, and ProPhoto, to mention a few. Each of these models express color differently. Each has its limitations and is best intended for particular cameras, displays and devices.
-----The gamut best used for printing is generally thought to be Adobe RGB (1998). One thing is for certain, which ever mode is chosen as a “working” color space, all images associated with a particular project should maintain the same mode in order to reproduce all images’ colors uniformly.
-----There is much more to the science of color management than can possibly be outlined here. Suffice to say that all three of these related building blocks MUST be controlled and respected if true quality control is expected.
-----Quality control should be a way of life to anyone in the business of reproducing photographic images in print.
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