Scanner resolution details - set the program

VI. Reference Scheme for Setting Resolution

For beginners, it is easy to take an arbitrary approach to the input resolution, scan at random with the highest resolution that the device can support, or use any value at will. In some cases, the image is sent naturally, regardless of the amount of information that the image should contain. More often than not, it is normal to think that it is unnecessary to simply delete any extra information or add additional information by re-sampling it later. These users did not realize that simply adding or subtracting data from the image would have a detrimental effect on the image, including sharpness, contrast, etc. Although some adjustments can be made to the image after making some unsuitable decisions during the scan, the best choice is to choose the best input resolution in advance.

1. Set the scan resolution with "division"

Experience has shown that using a value that can be divided by the optical resolution of the scanner as the input resolution during scanning is a simple and effective method. For example, for a scanner with an optical resolution of 600 dpi, common scan resolutions should be 600 dpi, 300 dpi, 200 dpi, 150 dpi, 100 dpi, 75 dpi, and the like. The reason why the resolution is determined by the "division method" is very simple. If one of the other input resolutions is selected, the scanning program must determine the color or gray value for a given pixel. Matching is performed and an average value is required, which tends to reduce the tone integrity of the original image.

What if the amount of information generated when scanning using a divisibility resolution is less than what is needed? In this case, a simple and reasonable rule is to scan with divisible resolution only above this resolution, and then The image is resampled (reduced pixels) during post-processing. In this case, it must be ensured that the re-sampling is only superfluous information, and the re-sampled image can still provide enough information for the output device to use.

2. Integral magnification factor scanning

It is also possible to scan using the divisible factor for the same reason as setting the scan resolution with "Division", ie, to avoid impairing the function of the scanner's optical system. For best results, scan at 100%, 200%, 300%, etc. of the original image size until it reaches (but does not exceed) the scanner's maximum optical resolution. If the amount of information obtained when using a certain divisor is not sufficient, the next magnification factor higher than this resolution can be used, and then the image can be re-sampled during post-processing (re-sampling means that after scanning, Use image processing software to reduce the resolution of the image to discard certain information, so as to obtain new images that meet the needs. This process is called resampling.

Below are some typical scan resolution settings for reference only.

1. For creating web pages or E-mail sending: 72-100dpl

2. General newspaper pictures: no more than 100dpi.

3. Color magazines, posters: 100~300dpi.

4. For OCR text recognition (black and white mode): 300dpi

5. General color photo: 300~600dpi

6. Fine: I mechanical drawings, architectural design: 1 200dpi

7.35mln positive film 1000 unload i or higher.

8.351llin negative 1 400 unload i or higher.

From the above introduction, there is no universal value suitable for all images in the scanning resolution. The ultimate goal is to obtain a proper amount of information to meet the output requirements. We can calculate the appropriate scanning resolution based on the following basic questions:

1 How large is the size of the original image? If you only want to scan a portion of the original, you can enter the size to be scanned into the scanner's setup screen.

2 What kind of media is the image to be output? Is it a printed matter, a multimedia video device, or a film?

3 What is the final output size? Is A4 or A37? If output to a printed crystal, its size varies depending on the image; other output media have a fixed size, and thus can reasonably determine how much information should be contained in an image. ·

4 If the output is a print (print) media, is the final output device a halftone printer or a continuous-tone printer? What is the resolution of the printer?

5 What is the color depth of the scanned image? Is it a line drawing (1 bit), a grayscale (8 bits), or a color picture (24 bits)?

The higher the scan resolution is, the clearer the image is, but considering that if the resolution of the original device or the output device is exceeded, then a clear image may not come out, and it takes up a lot of disk space, which has no practical value. Therefore, it is necessary to choose the proper scanning resolution. You can scale down large images after scanning.

In addition, the resolution is not the only factor that determines the quality of a scanned image. Equally important are the factors such as the dynamic density range of the scanner. They can determine the purity of the color and the sharpness of the details. However, if the resolution can be handled correctly, the continuous tone can be imitated by providing an appropriate amount of information and information density, thereby greatly improving the scanning effect.