Here's an article on how the Frontier machines work.
http://tech2.nytimes.com/mem/technology/techreview.html?res=9E05EFD8153CF937A15753C1A9649C8B63
HOW IT WORKS; Color Prints, Laser-Tweaked and Sharper Than Ever
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By ROY FURCHGOTT [/SIZE]
Published: October 24, 2002
IN the days before digital cameras and inkjet printers, photographic prints were made by exposing chemically treated paper to light, then bathing it in vats of yet more chemicals. Photo imaging has come a long way, but the route to stunning images still ends with the exposure of special paper to light and chemicals. The difference is this time the light is not from an ordinary bulb, but from color lasers in the most advanced digital commercial film printers. Anyone who has seen the outstanding images that commercial inkjet printers can produce might wonder why they need improvement. As sharp as pictures are with some inkjet equipment, the sharpness is limited. Inkjets spray little puffs of ink, so the edges of the dots tend to be blurry, like dots from a can of spray paint. That makes fine details in photos less crisp. The more intense the color, the more intense the ink spray required, and the greater the blur.
Laser-based digital labs -- which are manufactured by companies like Fuji, Noritsu and Agfa and used by quick-photo shops and drugstores -- avoid that problem because the pinpoint of light stays the same size no matter how intensely it is fired. That results in sharper details when the laser exposes the silver halide crystals on the photographic film.
These lasers are not the same as those found in an office laser printer, even color models. Those office machines work like a copier -- a laser light puts an electrostatic charge on a drum that picks up toner (either black or colors) and fuses it to paper. In the photo lab, there are actually three colors of laser that fire little dots of light on roughly the same kind of photo paper that has been used for 100 years.
Getting color lasers to the lab wasn't easy. Engineers had to overcome costly technical hurdles that had made laser printing a seeming impossibility. Although it was easy to make an inexpensive and reliable red laser -- those $10 pen pointers have one -- scientists needed lasers that produced green and blue light as well. Without those three colors, they could not mix the rainbow palette needed to reproduce color photographic images. But blue and green lasers were expensive and had a short life span.
The Fuji Corporation, which says it makes 60 percent of the laser processors used at photo labs, solves the problem by using lasers that emit infrared light, outside the visible range. The invisible light then passes through a harmonic generator, which doubles the frequency of the beam, making it visible as blue or green. Other companies have employed different methods, like using gas lasers, to generate the colors.
The real magic of these digital systems takes place before the photons hit the paper. The machines have high-speed scanners that can accept negatives, positive transparencies -- like slides -- or photo prints, and they can also handle digital image files, from CD's or memory cards. The image is then analyzed by software that adjusts color, contrast and exposure as needed.
Older bulb-based printers do that too -- but they have to choose the best averages before exposing a negative to the even light of the enlarger bulb. The laser printers can choose a custom exposure for each part of the photo -- essentially instructing the lasers to darken underexposed areas and lighten overexposed ones -- giving it far greater ability to rescue poor images.
The extra features of laser-based models mean they cost more too -- a digital minilab, like a Fuji Frontier, can cost $100,000 or more, depending on features and speed. But there are limits to what even the laser software can do. While it does well correcting color, it cannot do much to reduce bad shadows. For that kind of correction, it still takes an image-editing program like Photoshop and a skilled operator.
Once a photo is scanned, the software makes adjustments and sends the information to fire the lasers. Because the lasers themselves do not move, the light is bounced off a rotating six-sided mirror that reflects the light dots onto the paper. As the mirror turns, it draws a line across the paper in light. Each full rotation makes six lines of color image, then the paper advances to take the next six lines.
The rotating mirror reflects the light through a lens and off two stationary mirrors that make sure the light hits the paper at a perpendicular angle. Otherwise, the scan lines would have fuzzy edges, like those produced by an inkjet. Using a digital camera and a laser developer, it is possible to produce photos that are clearer and more detailed than what film cameras produce. Digital images also lack the grain that is on film negatives.
But as Fuji discovered with an early version of its laser processor, detail can be too much of a good thing. ''The machine was too sharp -- you'd see every blemish,'' said Brad Bunk, a senior technical specialist at Fujifilm. Later machines added a facial recognition feature. When it detects a rounded surface in skin color, the software smooths the surface so that every pore isn't apparent, which is especially important since these prints can last 200 years.
