تغيير جودة الفيلم .. المعالجة والطباعة .. كيفية التقاط وتطوير الصور بالأبيض والأسود

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  • تغيير جودة الفيلم .. المعالجة والطباعة .. كيفية التقاط وتطوير الصور بالأبيض والأسود

    تغيير جودة الفيلم .. المعالجة والطباعة .. كيفية التقاط وتطوير الصور بالأبيض والأسود

    ALTERING FILM QUALITIES

    Deliberate over- and under - exposure not only affect the density of the nega- tive , but the contrast also . This is a valuable technique for controlling the image and is , incidentally , an important part of using the Zone System described earlier . Because there are only tones to think about , altered development is a much simpler and more useful technique in black - and - white than it could ever be in colour .

    If you increase the development , the tonal range is expanded , and so the contrast is increased . If , on the other hand , the development is decreased , the

    If the aim is to reduce contrast from the average ( below ) , then the tonal range may be compressed by decreasing the development of the print ( left ) .

    RIGHT If development of a print is increased , the tonali range is expanded , with the result that contrast is boosted .

    Altering Film Development

    Under - development lowers contrast and so extends the tonal range ( far right ) . Over - development increases contrast , compressing the tonal range . ( right ) . Therefore , with a high contrast subject , where bright highlights and dense shadows cannot both be recorded on a normally processed negative , under- developing the film ( by shortening the time or diluting the chemicals ) will help . To compensate , the exposure will have had to have been increased . On the other hand , if the subject is flat , increasing the development ( by extending the time , raising the temperature or increasing the concentration of developer ) will make the image more lively . In this case , the exposure must have been reduced . For this type of contrast control , adjustments in the order of a half or one f - stop are normally made .

    tonal range is compressed and the contrast reduced . This means , for example , that a scene with a limited range of tones , such as on a dull day , can be given more life by push - processing the film . If you are using this technique only to control the contrast , remember to adjust the exposure setting accordingly . Should you plan to reduce contrast by under - developing one stop , for instance , the lens aperture will have to be opened up or the shutter speed slowed down by the equivalent amount . Alternatively , you could alter the film speed rating : for one - stop underdevelopment of Tri - X or HP5 , rate them at ISO200 instead of ISO400 .

    The actual procedure varies according to the film / developer combination , and there is even some choice . There are three things that affect the degree of development : the development time ; the temperature ; and the strength of the developer solution . In theory , changing any of these will do the job , but the limits are set by the need for an evenly processed image . Under - development in particular is limited by this , and for this reason it may be better to use a special low - contrast developer ; development times should be at least more than 5 minutes . Overall , the most commonly used technique is altering the time ( this is the only practical choice available to a professional lab , which is processing quantities of film at time most of it normal ) .

    SPEED vs CONTRAST

    Because altered processing changes both the strength and contrast of the image , it is important to be clear about the effect that you want . Push - proces- sing can be used as a technique for photographing in low light or for higher contrast , or for both . The film speed is adjustable , but the increase in contrast is inevitable , as is an increase in grain . In particular , the shadow areas ( those which receive least exposure and so are palest in the negative ) tend to lose detail , and block up into solid areas of black when the negative is printed . Graininess , as we saw earlier , becomes most obvious in mid - toned areas .

    For maximum film speed , select a fast film to begin with , as push - processing a slow or medium film is always less effective than using a film that has been designed for its great sensitivity to light . On the other hand , if you want only to increase the contrast , it is more effective if you choose a slow film - this is already slightly more contrasty than faster emulsions .

    Pull - processing is less commonly used , simply because of the circumstances in which most photographs are taken . There is insufficient light for photography more often than there is too much , and the requirement for high contrast in a scene is more usual than lowering it .

    Although all of the above assumes that you have planned to change the development from the start , these are also useful emergency procedures in cases where you have made an exposure mistake . The most common is forget- ting to change the meter setting or film speed dial when changing film types . If this happens , simply continue shooting at the ' wrong ' setting ( provided that it is within a correctable range , between about 2 stops under and 3 stops over ) , and make the adjustments to the development .

    Under - development gives low contrast ( above ) , over- development gives high ( above right ) . The second shot had been under - exposed to allow for over - development .

    ABOVE One by product of the increase in contrast that results from push processing is a loss of detail in shadow areas , which tend to block into solid black Graininess , meanwhile , becomes most obvious in mid toned areas .

    اضغط على الصورة لعرض أكبر. 

الإسم:	CamScanner 03-10-2024 14.18_1.jpg 
مشاهدات:	22 
الحجم:	126.6 كيلوبايت 
الهوية:	239622 اضغط على الصورة لعرض أكبر. 

الإسم:	CamScanner 03-10-2024 14.19_1.jpg 
مشاهدات:	13 
الحجم:	183.5 كيلوبايت 
الهوية:	239623 اضغط على الصورة لعرض أكبر. 

الإسم:	CamScanner 03-10-2024 14.21_1.jpg 
مشاهدات:	12 
الحجم:	168.5 كيلوبايت 
الهوية:	239624 اضغط على الصورة لعرض أكبر. 

الإسم:	CamScanner 03-10-2024 14.22_1.jpg 
مشاهدات:	12 
الحجم:	117.8 كيلوبايت 
الهوية:	239625 اضغط على الصورة لعرض أكبر. 

الإسم:	CamScanner 03-10-2024 14.23_1 (1).jpg 
مشاهدات:	11 
الحجم:	132.6 كيلوبايت 
الهوية:	239626

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