Converting digital color images in black and white? What could be simpler!Inexperienced newcomer will offer use the Desaturate, available in almost any graphics program. Highly professional advise to convert manually using one of the standard approaches described in the user manual for the package Photoshop.
From time to time I ever participate in discussions on the topic, what method (filter, process and t on) is better and why. This paper – rather a summary of my subjective point of view, not a test. Nevertheless, it was placed in the “Small unscientific tests” as the argument is based largely on a comparison of two procedures for the conversion: 1. automatic filter B / W from the package PhotoFreebies (plug-in for Photoshop);
2. Tool Channel Mixer (Photoshop), calculated on the creative user. Other (well known and described in detail in other sources) how to convert images to black and white is not mentioned in this article, simply because my plans never included the writing of a comprehensive and exhaustive review. What is the problem? Easy Desaturate often can not cope with the problem satisfactorily convert color images into black and white for two main reasons: 1. The color contrast is not always coincide with the luminance contrast. Typical example: red titles. On a bright background of the summer foliage, such letters can be read quite well. However, when converting images to black and white “readability” inscriptions by anyone other than a very bright red color, may significantly deteriorate. 2. At half-tone images brightness gradients, often giving the expressiveness of the individual elements are perceived differently depending on the color of the original fragment. In traditional black and white photography, these problems were solved through the use of color filters, allowing to achieve the desired tonovosproizvedeniya colored objects. In color digital photos are appropriate to solve the problem using methods of computer processing. Fig.1 The original test image The problem with color and black and white contrasts can be illustrated, for example, using the test image shown in Fig. 1. Transform it into a black and white with a few software tools. Fig. 2 transformation using the Desaturate (Photoshop) As seen from Fig. 2, application of the standard function Desaturate in this case leads to more or less acceptable outcome. Only the red color on a yellow background was not enough contrast. Can I get a better result by using more advanced tools? Fig. 3 Output transformation with the filter B / W from the package PhotoFreebies Package PhotoFreebies (Fig. 3) yielded excellent results, in terms of contrasting playing characters. However, the color red in this case was almost black. Under other circumstances, this effect could be undesirable. In other words, an acceptable contrast does not always lead to a natural (or required) the transfer of semitones. Fig. 4 Result conversions with Channel Mixer (R = 50%, G = 41%, B = 9%) Fig. 4 shows the result of the conversion tool to Channel Mixer. The parameters in this case non-optimal. However, most guidelines recommend them as a quite good first approximation for further change. In my opinion, from viewing images presented in Fig. 2-4, should be only one obvious conclusion: different procedures yield different results. Therefore, in practice it is desirable not to limit yourself using a single tool. This is especially true for fully automatic procedures. Converting real picture
Now let’s see whether the differences between the methods is equally obvious, if the transformation is not subjected to a test image file, but the real photographic image. As the test pictures we take the photograph, shown in Fig. 5. It has elements of both with a very small and very big contrast. We pose the problem as follows. When converting the image into black and white is required: 1. To emphasize the presence of clouds in the sky. In other words, we must try to avoid the transformation of the sky in a dreary gray area. 2. Save as possible all the architectural details of the palace. Most problematic in this respect are molded socket between the windows of the second and third floors. Fig. 5 Test picture We turn first to the said standard procedures (see Figure 6).. Fig. 6 (a, b, c) Fig. 6a shows the result of the simplest operations Desaturate. In general, the picture is quite acceptable. However, the clouds could not focus. The image in Fig. 6b was obtained by the above filter, B / W from the package PhotoFreebies. If the previous test, this filter has led to the best results (according to the criterion “readability of the letters”), then in this case, he, unfortunately, is clearly not lived up to his expectations. From the sky not only virtually disappeared clouds, but the plaster rosettes have turned out very faint. Application Tool Channel Mixer (R = 70%, G = 23%, B = 7%) has improved the situation with playback of clouds (Fig. 6c). But the outlet is almost completely disappeared. Obviously, to obtain optimum feed should be mixed in different proportions. Analysis of individual channels shows that in this case a contrasting display of clouds against the sky meets the red channel (R), a molded socket satisfactorily appears in the blue channel (B). Therefore, these two channels should play a decisive role in this case. Disabling uninformative green channel (G = 0) and try to find the correct ratio between the remaining two channels. Photo shown in Fig. 7, was obtained with the Channel Mixer tool for the following parameters: (R = 70%, G = 0%, B = 30%). As a result, managed to achieve exactly the same time Visibility and clouds, and stucco. Fig. 7 Cost the game worth the candle? How justified was the effort? There is no doubt that the answers will depend on the particular case. Universal recommendations do not exist. In color television, the luminance signal is formed based on the following formula: Y = 0,3 R + 0,59 G + 0,11 B. It serves as the dominant green channel, since the human eye is most sensitive to it and differentiates it the greatest amount of detail. In the thus formed broadband luminance channel is transmitted as much information about the details in the image.The other two color difference signals have a much narrower range, ie information about the details sent to them much less. It should however remember (and understand) that the color television and computer processing of images – they are two different areas of knowledge. Automatic (mindlessly) transfer rules from one area to another should not. A more detailed discussion of this aspect is beyond the scope of this publication. Conclusions and recommendations As in the remainder of the section “Small unscientific tests,” from stiff conclusions and recommendations, I will refrain here. Professionals are unlikely to need. New to the same, as well as those who do not want to spend time to study the theory, I would recommend the following procedure of trial and error: 1. Try to apply the standard procedure Desaturate.
2. See all the image channels (Channels). Who knows? Perhaps one of the channels just contains the same image that you want?
3. Apply one of the many automatic filters (for example, B / W from the package PhotoFreebies). It is only important to understand that there is no automatic, as if he was not perfect, is not guaranteed to be able to lead to success in 100% of cases.
4. If none of the above described does not produce the desired result, then nothing is left to do, how to master one of the methods of manual conversion.
From time to time I ever participate in discussions on the topic, what method (filter, process and t on) is better and why. This paper – rather a summary of my subjective point of view, not a test. Nevertheless, it was placed in the “Small unscientific tests” as the argument is based largely on a comparison of two procedures for the conversion: 1. automatic filter B / W from the package PhotoFreebies (plug-in for Photoshop);
2. Tool Channel Mixer (Photoshop), calculated on the creative user. Other (well known and described in detail in other sources) how to convert images to black and white is not mentioned in this article, simply because my plans never included the writing of a comprehensive and exhaustive review. What is the problem? Easy Desaturate often can not cope with the problem satisfactorily convert color images into black and white for two main reasons: 1. The color contrast is not always coincide with the luminance contrast. Typical example: red titles. On a bright background of the summer foliage, such letters can be read quite well. However, when converting images to black and white “readability” inscriptions by anyone other than a very bright red color, may significantly deteriorate. 2. At half-tone images brightness gradients, often giving the expressiveness of the individual elements are perceived differently depending on the color of the original fragment. In traditional black and white photography, these problems were solved through the use of color filters, allowing to achieve the desired tonovosproizvedeniya colored objects. In color digital photos are appropriate to solve the problem using methods of computer processing. Fig.1 The original test image The problem with color and black and white contrasts can be illustrated, for example, using the test image shown in Fig. 1. Transform it into a black and white with a few software tools. Fig. 2 transformation using the Desaturate (Photoshop) As seen from Fig. 2, application of the standard function Desaturate in this case leads to more or less acceptable outcome. Only the red color on a yellow background was not enough contrast. Can I get a better result by using more advanced tools? Fig. 3 Output transformation with the filter B / W from the package PhotoFreebies Package PhotoFreebies (Fig. 3) yielded excellent results, in terms of contrasting playing characters. However, the color red in this case was almost black. Under other circumstances, this effect could be undesirable. In other words, an acceptable contrast does not always lead to a natural (or required) the transfer of semitones. Fig. 4 Result conversions with Channel Mixer (R = 50%, G = 41%, B = 9%) Fig. 4 shows the result of the conversion tool to Channel Mixer. The parameters in this case non-optimal. However, most guidelines recommend them as a quite good first approximation for further change. In my opinion, from viewing images presented in Fig. 2-4, should be only one obvious conclusion: different procedures yield different results. Therefore, in practice it is desirable not to limit yourself using a single tool. This is especially true for fully automatic procedures. Converting real picture
Now let’s see whether the differences between the methods is equally obvious, if the transformation is not subjected to a test image file, but the real photographic image. As the test pictures we take the photograph, shown in Fig. 5. It has elements of both with a very small and very big contrast. We pose the problem as follows. When converting the image into black and white is required: 1. To emphasize the presence of clouds in the sky. In other words, we must try to avoid the transformation of the sky in a dreary gray area. 2. Save as possible all the architectural details of the palace. Most problematic in this respect are molded socket between the windows of the second and third floors. Fig. 5 Test picture We turn first to the said standard procedures (see Figure 6).. Fig. 6 (a, b, c) Fig. 6a shows the result of the simplest operations Desaturate. In general, the picture is quite acceptable. However, the clouds could not focus. The image in Fig. 6b was obtained by the above filter, B / W from the package PhotoFreebies. If the previous test, this filter has led to the best results (according to the criterion “readability of the letters”), then in this case, he, unfortunately, is clearly not lived up to his expectations. From the sky not only virtually disappeared clouds, but the plaster rosettes have turned out very faint. Application Tool Channel Mixer (R = 70%, G = 23%, B = 7%) has improved the situation with playback of clouds (Fig. 6c). But the outlet is almost completely disappeared. Obviously, to obtain optimum feed should be mixed in different proportions. Analysis of individual channels shows that in this case a contrasting display of clouds against the sky meets the red channel (R), a molded socket satisfactorily appears in the blue channel (B). Therefore, these two channels should play a decisive role in this case. Disabling uninformative green channel (G = 0) and try to find the correct ratio between the remaining two channels. Photo shown in Fig. 7, was obtained with the Channel Mixer tool for the following parameters: (R = 70%, G = 0%, B = 30%). As a result, managed to achieve exactly the same time Visibility and clouds, and stucco. Fig. 7 Cost the game worth the candle? How justified was the effort? There is no doubt that the answers will depend on the particular case. Universal recommendations do not exist. In color television, the luminance signal is formed based on the following formula: Y = 0,3 R + 0,59 G + 0,11 B. It serves as the dominant green channel, since the human eye is most sensitive to it and differentiates it the greatest amount of detail. In the thus formed broadband luminance channel is transmitted as much information about the details in the image.The other two color difference signals have a much narrower range, ie information about the details sent to them much less. It should however remember (and understand) that the color television and computer processing of images – they are two different areas of knowledge. Automatic (mindlessly) transfer rules from one area to another should not. A more detailed discussion of this aspect is beyond the scope of this publication. Conclusions and recommendations As in the remainder of the section “Small unscientific tests,” from stiff conclusions and recommendations, I will refrain here. Professionals are unlikely to need. New to the same, as well as those who do not want to spend time to study the theory, I would recommend the following procedure of trial and error: 1. Try to apply the standard procedure Desaturate.
2. See all the image channels (Channels). Who knows? Perhaps one of the channels just contains the same image that you want?
3. Apply one of the many automatic filters (for example, B / W from the package PhotoFreebies). It is only important to understand that there is no automatic, as if he was not perfect, is not guaranteed to be able to lead to success in 100% of cases.
4. If none of the above described does not produce the desired result, then nothing is left to do, how to master one of the methods of manual conversion.