تويت
التقنية الأساسية .. المعالجة والطباعة .. كيفية التقاط وتطوير الصور بالأبيض والأسود
PROCESSING & PRINTING
BASIC TECHNIQUE
Processing black - and - white film is one of the simplest procedures in photo- graphy , and certainly easier and quicker than processing colour materials . There are five stages : developing , stop bath , fixing , washing and drying . By the time the processing is about to begin , the film has been exposed , and carries what is known a a ' latent ' image . Those silver halide crystals that have been struck by light have undergone a very small reaction that needs the help of a developing solution before it can be seen .
The developer acts on the exposed crystals , and converts them into metallic silver , which is black and stable . The timing controls the quantity of black silver , and if the film were left in the developer too long , the image would eventually be obliterated . So , once the developer has acted for long enough , it is poured away and replaced with a stop bath . This completely halts any more development , and is a good idea because , even with the tank freshly emptied , drops of developer remain on the emulsion . Following this , the fixing solution dissolves away the remaining unexposed silver halide crystals . Washing removes all traces of fixer and the dissolved halides , and must be thorough , or else the image that the negative carries will not stay permanent .
For equipment and materials , look back to the earlier section of this book . In addition to these basic items , you will need the following chemical solutions : developer ; stop bath ; fixer ; and a recommended optional extra - wetting agent . Of these , there is an important choice only in the developer . Several manufacturers produce solutions that are essentially similar in action , and the most convenient choice is usually the one recommended in the instruction leaflet packed with the film .
Developers are supplied in powder or liquid concentrates , and must be mixed and diluted before use . Normally , there are two alternative methods of use : to mix just enough for the number of films you intend to develop , discarding the used developer each time ; or making up a larger quantity and re - using it . If you re - use developer , the time must be increased progressively . For instance , with Kodak's D - 76 , a typical standard developer , The first two uses can be performed at the recommended time , the next two for 6 % longer , and the fifth and sixth for 12 % longer . After that , throw the solution away . With this method , which saves money , you must keep a careful note on the storage bottle of how often it has been used .
ABOVE The production of a visible black and white image is a simple matter of realising the ' latent ' image already present on the exposed frame of film . This is achieved by immersing the film in developer , which acts on exposed silver halide crystals , converting them into metallic silver , which is black and stable .
LEFT Examining negative strips is easiest on a light box ; the large format negative is going to cause some difficulties in printing , because of the extreme contrast in the original scene .
PROCESSING & PRINTING
BASIC TECHNIQUE
Processing black - and - white film is one of the simplest procedures in photo- graphy , and certainly easier and quicker than processing colour materials . There are five stages : developing , stop bath , fixing , washing and drying . By the time the processing is about to begin , the film has been exposed , and carries what is known a a ' latent ' image . Those silver halide crystals that have been struck by light have undergone a very small reaction that needs the help of a developing solution before it can be seen .
The developer acts on the exposed crystals , and converts them into metallic silver , which is black and stable . The timing controls the quantity of black silver , and if the film were left in the developer too long , the image would eventually be obliterated . So , once the developer has acted for long enough , it is poured away and replaced with a stop bath . This completely halts any more development , and is a good idea because , even with the tank freshly emptied , drops of developer remain on the emulsion . Following this , the fixing solution dissolves away the remaining unexposed silver halide crystals . Washing removes all traces of fixer and the dissolved halides , and must be thorough , or else the image that the negative carries will not stay permanent .
For equipment and materials , look back to the earlier section of this book . In addition to these basic items , you will need the following chemical solutions : developer ; stop bath ; fixer ; and a recommended optional extra - wetting agent . Of these , there is an important choice only in the developer . Several manufacturers produce solutions that are essentially similar in action , and the most convenient choice is usually the one recommended in the instruction leaflet packed with the film .
Developers are supplied in powder or liquid concentrates , and must be mixed and diluted before use . Normally , there are two alternative methods of use : to mix just enough for the number of films you intend to develop , discarding the used developer each time ; or making up a larger quantity and re - using it . If you re - use developer , the time must be increased progressively . For instance , with Kodak's D - 76 , a typical standard developer , The first two uses can be performed at the recommended time , the next two for 6 % longer , and the fifth and sixth for 12 % longer . After that , throw the solution away . With this method , which saves money , you must keep a careful note on the storage bottle of how often it has been used .
ABOVE The production of a visible black and white image is a simple matter of realising the ' latent ' image already present on the exposed frame of film . This is achieved by immersing the film in developer , which acts on exposed silver halide crystals , converting them into metallic silver , which is black and stable .
LEFT Examining negative strips is easiest on a light box ; the large format negative is going to cause some difficulties in printing , because of the extreme contrast in the original scene .
تعليق