Digital photo color correction processing Fluorescent lighting Photo

Standard fluorescent lighting is a big problem for high-quality color photography. General fluorescent lighting Color Reproduction index (CRI) is very unsatisfactory. The most commonly used fluorescent tubes inside commercial buildings still emit the ubiquitous cold white, which is bad for photography and contains a large amount of green and yellow peaks in the output spectrum. Photographs taken with daylight balance in such light sources will always be green.

To correct the green photos under these fluorescent lamps, you must use your eyes to determine the color balance, unless you have a known white or gray in the captured photos. The most important work to consider in most photography is to set the correct shooting conditions. This means using the white balance adjustment on the camera (if any) and using a gray card to shoot to help with tonal calibration (if you are working with files in Photoshop). A simple solution is to connect a. 30cc Green filter to the flash, and use the camera's automatic white balance to shoot. Even though this automatic white balance may be biased, the resulting picture generally has the same color balance as a whole.

Lower CRI makes it impossible to achieve high quality results, but careful color correction can achieve acceptable results. So, after learning that there is no easy way to fix this, here's how to fix this sort of snap Photo:

Figure 7-50 is a typical photo taken with the automatic white balance set in the fluorescent lighting of a large store. Considering the use of various types of lamps in lighting, the camera captures the lighting quite closely with the actual situation. Beth looks a little yellow, but it's basically satisfying.

Figure 7-50

If the camera is set to daylight balance, the problem will be noticeable when you open the image in Photoshop. As you can see in Figure 7-51, we have turned poor Beth into a Martian. If the image you are shooting is similar to the picture, you will know that the white balance of the camera is set to daylight when you take the picture.

Figure 7-51

The color bias is very serious, and the only fix for the image is some custom color correction. Using the color correction steps shown in this example, first try some of the simplest correction methods.

1, choose "Image" _ "Adjust" _ "Automatic Color". The automatic color correction may be correct or deficient, but the effect is greatly improved in the diagram, as shown in Figure 7-52. For the correction of such a serious image, "automatic color" even if there is a lack of, but also a great help.

Figure 7-52

2, the image is too dark. Use curves to lighten the image. This is a basic brightening curve adjustment (see Figure 7-53). As you can see in Figure 7-54, this "curve" adjustment makes the image brighter, but it can make the image better.

Figure 7-53

Figure 7-54

3, in the background there are many seemingly white and near-gray objects. Of course not completely sure, but there are always some guesses. There are three straws in the Curves dialog box. The eyedropper in the middle can change any color in the file to Gray by clicking the eyedropper in the document window. In many cases, a good color correction can be achieved by clicking around until you encounter a true neutral value in the image. There are three positions that appear to be good candidates, as shown in Figure 7-55.

Figure 7-55

Click Position 1 in Figure 7-55. This sample changes the image to cyan (see Figure 7-56, left). Paper stacks must be orange. Click Position 2 in Figure 7-55 to get a better result (see figure 7-56 for the middle figure). But the complexion looks too warm. The paper must have a cold hue. But with this temporary correction, it's easy to see what's actually going on in the background. A pile of books on the left shoulder looks like a good target. Click the eyedropper on the spine of the book Gray (see Figure 7-56, right). The effect of this sample is very close, but the image is still somewhat dark.

Figure 7-56

4. In the case of opening the Curves dialog box, let the image lighten up by moving the middle point up, similar to the position shown in Figure 7-53. This adjustment completes the correct correction (see Figure 7-57).

Figure 7-57

Another big problem with fluorescent lighting is when it comes to stimulating the camera's flash. Fluorescent lighting is more green than the flash of a camera, and the two kinds of lighting simply can't mix well. If the white balance setting is automatic when using the camera flash, the effect is likely to be as shown in Figure 7-58. The camera tries to compensate for the color balance, Beth turns magenta, and the background (outside the scope of the flash) turns green. If you don't use a large number of time-consuming masks, you won't be able to fix the problem, but there's a simple fix for shooting. Be able to shoot well with the flash, especially if the internal lighting is unstable and uneven, but there are definitely strange colors. The solution is to filter the Flash to match the lighting of the fluorescent light, or at least as close as possible to the fluorescent lamp.

Figure 7-58

Professional tips: In almost all business centers there are some natural reference points. The concrete staircase is close to the neutral color, PVC pipe, paper, ceiling coating, filing cabinet and so on. Just click around until you find the target of the neutral color. If the image is somewhat corrected, you can use the trusted Fade command.

The universal camera has a very small flash gun, so only a small filter is needed. Rosco Laboratoriesinc. The correction filters used in the production of movies also provide the filters you need, that is, the Rosco Tough Plus Green #3304. This filter is designed to turn daylight into cold white. So the daylight-balanced flash can match the cold white light. In other words, all the light turns into Goose green. The filter can be purchased at Calumet Photographic (www.calumetphoto.com) at a price of 7.49 dollars at the time the book was written.

The filter is large (20x24 inches), so it takes a long time to adapt. The filter is designed for light sources only and is made with hard polyester. If you want, you can use a. 30cc Green Camera Gel filter, but this small 3x3 inch filter has the same price as the above, as it is designed to be placed on camera lenses.

Cut a piece of filter that is slightly larger than the camera's flash and be taped to the tape, or use a special photographic grade copolymer to connect laterally with the adhesive material, the hot-pressing, and the catalyst-hardened connection, as shown in Figure 7-59. This configuration works well without fear of glue residue. If the filter is dirty or damaged, just cut another piece from the big filter.

Figure 7-59

In Figure 7-60, you can see the effect of using the. 30cc Green Camera Gel filter and the fluorescent white balance setting on the camera. As the photo shows, the color balance is much better than the original photo.

Figure 7-60

Category:

• PS Image Processing