Finding a resolution to the pixel saga.
Many of us find ourselves at a loss in all the digital jargon. What are pixels, dpi or lines per inch? How do I know what is appropriate for which media?
What are pixels?
Actually, it is quite simple.
Pixels are the digital equivalent of the photographic grain in film photography. Pixels are the smallest element of a digital picture containing color information. The more pixels there are in one square inch, the more precise is the color information. The graphic industries call this "resolution": the number of pixels per inch or dots per inch (dpi). So, "dots per inch" (dpi) is the same thing as "pixels per inch".
What is "lines per inch"?
"Lines per inch" is used only by the printing industry. It is a leftover from the time when, in order for pictures to be printed, they had to be superimposed on a semi-transparent screen with a certain number of straight lines per inch. The process was called half-toning. Newspapers, because of the coarse paper and fluid ink, have to use a coarse screen: 80 lines per inch. Magazines, on the other hand, use a finer screen, because of higher paper quality and ink holdout: usually 133 to 150 lines per inch (266-300 dpi).
The world of printing presses has not changed much. The basic process of printing with ink on paper at high speed is called offset printing and it has not changed significantly for over 75 years. The problem is to translate digital picture resolution (pixels per inch or dpi) into printer language of lines per inch. The formula turns out to be quite easy: you multiply lines per inch by two to get the correct resolution needed to print a digital picture. So, for example, for 80 lines per inch, you need a 160 dpi digital file; for a 150 lines per inch advertisement, you need a 300 dpi file.
Two questions arise from this equation:
What happens if the picture dpi is not high enough?
And why can't I just increase the dpi (pixels) to whatever I want?
The problem is that increasing the picture resolution artificially only increases the file size, not the picture information. Increasing the resolution of a picture simply duplicates (clones) existing pixels and the result is that the picture appears blurry. It is generally accepted in the printing industry that an increase of 10% is the maximum acceptable. It would be like blowing up a balloon with a drawing on it: the more it increases in size, the more the drawing appears muddy and unsharp.
Just because a picture appears sharp on the computer screen, it is no guarantee that the same picture file will print properly on the press. The resolution of a computer screen needs a file to be only 72 dpi (pixels per inch), whereas the average magazine requires a file of 300 dpi, that is four times higher. This is just one of the reasons why web browser pictures and other computer screen pictures are inadequate for printing presses. The other main reason is that web pictures are greatly limited in color space. Web pictures require only 256 different colors as opposed to the thousands needed for the printing press. In addition, for the file to work on a commercial press, it must be composed with a special reproduction curve, following the SWOP standard for offset presses. But, more on that another time.
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How will my pictures look?
We created a program to evaluate the picture collections and the scans provided to us on our clients' CD-ROMs. The CDs were intended for use by the media, particularly by travel writers and magazine editors. To our dismay, the quality of the scans provided on the CDs was not very high.
We found out that the scanners used were consumer grade equipment. Most desktop scanners come with a manual, but not with the years of training in photography, scanning, and printing media required to prepare a picture to be press ready.
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If you are a destination, your pictures are your brand they are your life blood.
Tourism and destination organizations go to great expense to prepare text and advertising copy for the press. All "t"s are crossed and the "i"s are dotted. The resulting ad copy is usually equal to none. Likewise, no expense is spared in building a topnotch photographic collection. But in this case, the quality control management hits some hidden challenges. It has been my experience that, after reviewing countless CD-ROMs and website Media Centers, very few contain pictures that are press ready.
What I found is not a pretty picture. Most pictures appear to be scanned in low resolution on flatbed desktop scanners, with at least one of the following defects (and sometimes several together): dust, heavy color cast, major color deterioration because of JPG compression, midtone and highlight loss of information — in short, a general lack of systematic color control. Scans are out of focus. Pictures labeled high-rez are often only 3"x5". Based on these findings, the marketing ROI is, in my opinion, questionable. CD-ROM production ranges from $8 to $10/unit, plus shipping, but how good are the files on it?
What is a proper scan?
A proper scan is defined as the digitization of an original that resolves the full range of its color nuances and contrasts, from specular highlights to deep shadow. As well, it is in focus to the photographic grain of the original. A photograph properly digitized, then, contains all the information of the original, ready to be enhanced at the discretion of the art director or designer. Therefore, scanning is not a question of aesthetic, but of technical acuity.
Nelson Vigneault, CEO, CleanPix Corp.
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