Adjusting the under-exposed image technology

In prepress design, some under-exposed manuscript pictures are often encountered. If they are left intact in the design draft, they will not only affect the effect of the entire design layout, but also damage the designer's creative taste. The magic of Photoshop is that it can make use of some of the tools it provides to easily adjust the images that are underexposed to restore their original appearance as much as possible.

1. Scan under-exposed images and enter your computer

Photographed with a digital camera. Data is entered into the computer and opened in Photoshop. Scanning a picture Setting the scan resolution can't be sloppy at all because it directly controls the re-imaging quality. In general, adhere to the following principles:

1 When the scanned image is used for color inkjet printing, the resolution of the color inkjet printer and the scaling factor of the image should be taken into account at this time. The resolution of the color inkjet printer refers to the output accuracy of various colors. It is not a true resolution. Dividing the resolution identified by the printer by the number of colors of the printer is its effective accuracy. For example, a four-color printer marked with a resolution of 720dpi or 1400dpi has an effective resolution of 180dpi and 350dpi.

When printing according to the size of the original image, the scanning resolution can be equal to the effective accuracy of the printer. If the image needs to be scaled for printout, the scanning resolution = scaling factor  output size ÷ original image size × × printer effective accuracy.

2 When the scanned image is used for printing, the number of printing lines and the image scaling factor should be taken into account at this time. The number of printing lines is the number of halftone units that can be printed per inch on the printing press. The unit is l/inlpi. The scaling factor is the output size and the original size. When printing is equal, the scanning resolution = number of printing lines × 2. For example, newspaper printing lines are generally 85 lpi, general color prints are 150 lpi, and exquisite pictures are 300 lpi. The corresponding resolutions are 175 dpi, 300 dpi, and 600 dpi, respectively. If the scaling image is printed, the scanning resolution = number of printing lines × 2 × scaling factor  output size ÷ original image size . In determining the problem of printing the network cable, do not just pursue a larger number of network cables, the better, although the larger the number of network cables, the actual image level and details are much more abundant, but the prepress design should also fully consider what kind of printing is used The paper, such as the 175-litre image printed on newsprint, will not only be subtle, but will cause blurring of the image and counterproductive. The author's personal experience is that: when using newsprint or offset paper offset printing, the printed cable is 80-100l; therefore, the resolution should be between 160dpi and 200dpi; if the coated paper below 210g is used for color printing, the printed cable can reach 175l. It should be between 200dpi and 300dpi. When high-grade copperplate paperboard with 210g or more color printing is used, the network cable can be set higher. In short, setting the resolution too high will cause a waste of time, and too low will affect the printing effect.

3 When the scanned image is displayed on the screen, generally speaking, the scanning resolution is set to 72 dpi if the display is large, and the resolution setting is 72 dpi × scaling factor if the display is zoomed.

Open in Photoshop due to the use of backlight when shooting, the subject is underexposure, and therefore the face of the character appears too dark image files.

2. Execute the "Image"/"Copy" command to copy the currently operated image as a separate copy. In the dialog box that pops up, click the OK button to confirm and copy the image.

3. Perform the "Image"/"Mode"/"Grayscale" command to convert the copied image mode from RGB to grayscale format.

4. Perform "Filter" / "Fuzzy" / "Gaussian Blur" command, according to the size of the image will be set to a suitable radius between 3 to 6 to determine the radius of the blur set in this example is 4.0, the image Make the appropriate blurring. î—¥

5. Now switch the current operation file to the original image file, execute the "Select"/"Load Selection" command, and the "Load Selection" dialog box will pop up. In the "Document" set to copy the image copy file name; "gray" in the "channel"; then "inverted" selected; "operation" option, select the "new selection." After the settings are completed, press OK to confirm that the selection is loaded into the image. At the same time, you can clearly see that the selection is just the underexposed part of the image.

6. The current operation file is converted to a copy image file, press the "Ctrl + W" key combination to close the image file, this time will prompt whether to save, select "No".

7. Run the "Edit"/"Fill" command to bring up the "fill" dialog and set the relevant options. Select "50% Gray" in "Use"; select "Color Dodge" in "Mode"; set to "100%" in "Opacity".

8. After the settings are complete, click OK to confirm that the image's selection is filled. Press "Ctrl+D" to cancel the selection.

Through the above eight steps of operation, it is easy to adjust a picture with a bad effect to be basically satisfactory. By adjusting, the brightness of the underexposed part of the original picture is improved, the details in the shadow range are fully expressed, and at the same time there is no influence on the brightness of other parts of the image. (Man/Yang Chun)