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Add transmission function to your scanner

recently, a friend came to play and saw my Microtek x12elu very envious, especially the attached lightlid35 glue host 1) peak power: ≤ 10 kW (including peripheral installations such as cooling and high-temperature installation); The film transmission adapter can scan negatives, but his scanner cannot. Now, although the home scanners on the market are very cheap, most of them can't scan the transmission documents, especially those with CIS structure, which makes many friends who want to input their photos (especially the inversion films and slides) into the computer and share them with you feel very sorry. In the past, the author has seen some experts use self-made props to transform scanners that cannot be scanned by transmission, but these productions are slightly more complicated. Two years ago, I also used this kind of scanner. At that time, after repeated experiments, I was able to scan the transmission manuscript, which affected the service life of the bulb and was very simple. The scanning effect was also good. Both CCD and CIS scanners could have a try. Take this opportunity to write an article. Maybe you can give some tips to friends who need it

scanning principle of transmission manuscript

in fact, the principle of transmission manuscript adapter is very simple, that is, use a light source to replace the original upper cover of the scanner, move the scanning light source from the bottom of the manuscript to the top of the manuscript, and let the light transmitted through the manuscript pass through the lens and several reflections, which is difficult: at present, the mirror is imaged on the CCD surface. According to the type of light source and scanning mode, the transmission document adapter can be divided into light source mobile type and light source fixed type. The thick upper cover of the former is like an inverted scanner. When scanning the transmission film, the lamp tube in the transmission document adapter runs synchronously with the imaging component below through the scanner, and scans the entire width together to obtain the transmission light image. In this process, the original light source in the platform scanner will not emit light, so as to avoid the reflection on the surface of the transmitted manuscript affecting the scanning effect. The fixed transmission adapter is like a small fluorescent lamp that emits uniform light, which only illuminates the entire scanning area and allows the imaging part to read the transmission information. Take the lightlid transmission scanning device of Microtek as an example. Its structure is very simple. It has no transmission parts and contains two cold cathode tubes, which are located on the left and right sides respectively. The light emitted by them is evenly distributed through the white material below

compared with reflection scanning, transmission scanning requires more stringent scanning equipment. First of all, one of the characteristics of transmission manuscript is that it requires high resolution of scanning equipment. Take the most common 35mm negative film in transmission manuscript as an example. Its image area is very small, only 36mm × 24mm, so the information density is very high. If you want to print it in A4 format, it is equivalent to 8 times magnification, which requires the scanner to have a very high optical resolution, so at least the scanner resolution is required to be 600 × Above 1200dpi

secondly, the density range of the transmitted manuscript is large, that is, the contrast between the bright and dark parts of the image is very strong. Especially the reverse plate. The range of light and dark that a scanner can distinguish is measured by the difference between the logarithm of the brightest part and the darkest part. The higher the number of color bits of the scanner, the more light and shade levels it can reflect, and the larger the dynamic range. In common transmission manuscripts, the density range of color negatives is smaller, and using a 24 bit or 30 bit scanner can also make do with it; The color reversal film must have a scanner with more than 36 bits. In fact, the best scanner color scale is above 42bit

required spare parts

if you have the basic hardware conditions for transmission scanning, you should prepare the following other important objects:

1. Transmission manuscripts to be scanned, such as photographic negatives, reverse films (slides), X-rays, etc

2. A mirror, the size of a wallet is OK; If there is a frame, remove it first. This is what I think is the simplest way to replace the transmission light source. The light from the scanner's own light source after specular reflection is used to develop the transmission draft. This "idea" came to my mind immediately after I understood the principle of the transmission adapter. Smart ^-^

3. A dark, non reflective and light tight paper, black is the best, and the thickness should not exceed the paper of the exercise book. In the middle, a hole the size of the image in the negative should be dug in advance, and the outer frame can be wider. Because the area of the negative film we scan is usually smaller than the width of the reflecting mirror, light will also be transmitted next to the manuscript during scanning. After these stray lights enter the sensor, they will affect the clarity and color of the scanned image, resulting in contrast deterioration. In order to solve this problem, it is necessary to have film frames corresponding to various film sizes, which can cover the area next to the picture during scanning, so as to ensure good image effect

4. A white transparent, uniform (important) and flat plastic sheet. At that time, I used a white plastic sheet placed in the plastic bag holding the negative film when I was developing and printing the photographic reverse film (negative film is not available); If there is no negative film bag, thin plastic bag or ground glass, the purpose is very simple, that is to weaken the light reflected by the mirror, otherwise the scanned things...

the next step is the scanning process, which is actually very simple. The main attention is to place the objects in order and order (see Figure):

place the negative film on the scanner glass plate, cover the negative film with dark paper, and expose the negative film in the hole dug in advance, Cover the exposed negative with a white plastic sheet, finally cover the mirror, close the cover of the scanner and start scanning

note that two kinds of indexes usually need to be established: document index and keyword index matters

wipe the glass plate of the scanner before scanning, otherwise the image will have a lot of black and white dots and lines (actually dust)

the negative film to be scanned should be placed in the center of the scanning starting line, which can minimize the distortion caused by the optical lens

when scanning, the upper cover of the scanner should be pressed, especially for CIS structure. Be careful not to crush the glass plate (it seems to be nonsense again)

when scanning, change the medium in the scanning software to transmission (positive or negative)

if you are free or often scan, you can make the above clip like an album. In the future, you can just insert the negatives during scanning

the pixels during transmission scanning must be higher than the reflection manuscript, because the negative itself is small and the particles are very fine. A 35mm negative is scanned into the computer at 300 dpi, but it is only 413 × 272 size. But if you scan with 600dpi, you can get 827 × 543

the scanned image will be processed by Photoshop or photoimpact and other software, and the effect will be better

the image quality scanned by this method is certainly not as good as that of a professional transmission scanner (even my x12elu), but if you can grasp the details, the scanned image will still surprise you

source: Shanghai Zhongjing Technology Co., Ltd

Copyright © 2011 JIN SHI