Introduction to Digital Color Enlarger Technology

Compared with other digital image output forms such as printers, digital color enlargement machines have many advantages. They can output high-quality photos, with very low consumable costs, and the photos can be preserved for a longer time.

As a perfect solution for digital image output, digital color enlarger mainly adopts the digital image output form of silver halide photographic paper. The color enlarger converts the digital image electrical signal into an optical signal, exposes it on silver halide photographic paper, and then uses the usual color photosensitive material washing process (such as RA-4 process) to obtain color photos after color development, bleaching and fixing.

Digital color enlargement machine can use many methods to realize the digital image silver halide paper, the commonly used methods are:

CRT technology : CRT is the abbreviation of Cathode Ray Tube, which means cathode ray tube. CRT technology uses cathode ray tube to convert the electrical signal sent to it into light signal image exposure on color paper. The earliest digital color enlargement machine adopts CRT technology.

However, the shortcomings of CRT technology are obvious. First, cathode ray tubes generally have few pixels, so it is impossible to produce large and clear photos using ordinary CRTs. The size of the output photos can generally be less than 8 inches. Second, the CRT method must use a lens to enlarge or reduce the CRT image to the required size before exposing the photo paper. Enlarging or reducing the image with a lens will produce various distortions on the image. In addition, the color gamut of the CRT does not match the color gamut of color photographic paper, and it cannot show tens of millions of colors and rich picture levels. The colors and levels of the photos produced are not clear. Finally, CRT technology also has weaknesses such as easy magnetization, poor field balance of the produced photos, and color imbalance.

At present, equipment using CRT technology has basically been gradually eliminated.

LCD technology : LCD is the abbreviation of Liquid Crystal Display, which means liquid crystal display. The LCD method uses the combination of liquid crystal panel and light source to expose photographic paper. That is, while the back of the LCD panel is irradiated with light source, digital electrical signals are sent to the LCD panel. The LCD panel makes each pixel on it show transparent and opaque changes according to the received digital electrical signals. As a result, the light from behind passes through the LCD panel, the "digital film", just like passing through ordinary film, so that the digital image is exposed on the photographic paper.

The advantage of LCD technology is that the LCD panel can be placed on the exposure window of the color enlarger where the film is placed, replacing the traditional film with this "digital film", making it easy to digitize the traditional color enlarger. This is a simple way to rejuvenate existing color enlargers in the digital age.

LCD technology has obvious advantages, but it also has many shortcomings. The biggest shortcoming is that the LCD panel has few pixels, only a few hundred thousand to one or two million. Such a number of pixels can neither fully utilize the more than 3 million pixels of the current mainstream digital cameras, nor can it produce large and clear photos. However, for color enlargers that can usually only enlarge 5-inch wide photo paper, it is fully capable of doing so. The number of colors that can be expressed is small, the color gamut does not match the color gamut of color photo paper, and the color gamut range is small, which is also a shortcoming of the LCD method. The LCD method cannot meet the production of particularly large digital photos, and because of the complex structure of the LCD, its imaging speed is very slow, which is also a shortcoming.

The principle of this exposure method is to use the light source penetrating from behind the liquid crystal panel to expose the traditional photo paper and process it into a digital photo. Its working principle is the same as the digital projector we use. LCD exposure method was quickly replaced by Lcos device exposure not long after it appeared, because it can efficiently use the backlight source.

At present, LCD models are the main models in the color enlargement market.

LCOS technology : Liquid Crystal on Silicon (LCOS) is a new digital imaging technology. It uses semiconductor CMOS integrated circuit chips as the substrate of reflective LCD. A thin layer of liquid crystal silicon is coated on the CMOS chip. The control circuit is placed behind the display device to improve the light transmittance, thereby achieving greater light output and higher resolution. The biggest advantage of LCOS technology is its high resolution.

LCOS models have obvious advantages and are the representative of new technologies. The "Yinglong" digital color enlargement equipment adopts this internationally advanced and domestically leading new technology. The photos produced by the "Yinglong" equipment are brightly colored, rich in layers, and have a strong field balance. In addition, the "Yinglong" equipment is very stable and has a long service life of the light source.

LED technology : Light Emitting Diode (LED) for short. This is a fully solid-state display device. The fully solid structure ensures that the device has extremely high reliability and extremely long life. It has the longest life of all display devices. Although it is composed of chips, reflective cavity, and sealing glue, it does not seem to be a flat-panel display, but the large-screen advertisements and promotional devices made with it are classified as large flat-panel displays.

Among all photoelectric conversion devices, LED has the characteristics of stable light emission and long life. LED digital imaging equipment has the advantages of stable performance and low equipment maintenance cost. The digital color enlargement machine using LED light source exposure technology uses LED exposure to print the digital image in the computer on digital photo paper using traditional silver halide technology. The LED exposure component has a long service life and is relatively cheap compared to laser technology.

DLP technology : Digital Light Processor (DLP) for short. That is to say, this technology first processes the image signal digitally before projecting the light. Its characteristics are first digital advantage. The adoption of digital technology improves the grayscale level of the image, eliminates image noise, stabilizes the picture quality, and makes the digital image very accurate. Secondly, it is reflective advantage. The application of reflective DMD devices greatly improves the total light efficiency of the imaging device, and the contrast and brightness uniformity are very good. The DLP projector has high clarity, uniform picture, sharp color, and the three-chip machine can achieve very high brightness, and can be zoomed at will, which is very convenient to adjust.

LASER technology : LASER is a laser that converts digital electrical signals into red, green and blue light through red, green and blue laser tubes to expose the photo paper. Laser has the characteristics of good monochromaticity and almost no diffusion, which brings the characteristics of LASER method to produce photos with high clarity, sharpness and very bright colors, and it is easy to achieve large-scale exposure.

LASER technology sends laser beams directly to photographic paper to make it sensitive to light. It does not require the participation of imaging lenses. Generally, three different colors of laser beams emitted by red, green, and blue lasers are converged together and then sensitive to light on the photographic paper. Therefore, there is almost no color drift, and there is no phenomenon of different image clarity at the edge and middle of the picture.

LASER technology has a short history, but it has developed very rapidly. It has almost dominated the world of large-format digital image output. To output large-format digital photos with a width of more than one meter and a length of several dozen meters, laser technology is the only way. If the width of the digital image is wider than the maximum format that the output device can output, the software of many laser digital image output devices will automatically divide the digital image into several outputs, so that it can be easily spliced ​​to obtain a digital photo with a larger width. The splicing can be very accurate because the output accuracy of laser output devices is very high.

LASER is the most advanced digital printing and enlargement equipment on the market. Most of the representative models are Fuji. The disadvantage is that the price is too high! The price is more than 1 million RMB. The life of the laser head, the main component of the equipment, is not very long.

Laser technology is also the future development trend of digital color enlargement equipment.

LDD technology : LDD exposure digital processors seem to be the leading models in the market. They use a large-screen high-definition cathode ray tube, and in fact they should also belong to the CRT exposure method. However, their image pixel value has reached 10 million to 40 million, and they can produce 18-inch high-definition digital photos. Domestic brands include Duoli, Sofia, Tianda, etc. There are also such products abroad, but due to price reasons, not many of them flow into the domestic market! Geometric distortion of the edge of the photo in the screen exposure method is inevitable.

FOCRT technology : FOCRT is the abbreviation of fiber cathode ray tube. Fiber cathode ray tubes are different from ordinary cathode ray tubes. They expose color photographic paper through optical fibers with fluorescent material ends. The advantage of FOCRT is that the light is directly transmitted to the photographic paper through the optical fiber, and the output photos basically eliminate distortion. FOCRT exposure method can obtain high-quality digital photos.

Laser head exposure is the most excellent and high-end digital color enlargement equipment. Million-dollar digital equipment on the market all use laser exposure, and the quality of enlarged photos is much better. Large color enlargement shops such as Jinan "Yellow River" use laser color enlargement machines.