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SLOW OR FAST ?
Film speed and graininess are inextricably linked . If you choose a fast film because it will be easier to use in low levels of lighting , the image will be more grainy and so show less detail . If a grain - free image is important , you must choose a slow film . The reason for this is that , like basic black - and - white film , colour emulsions rely on silver grains to form the image . During the processing , these are replaced by coloured dyes , but in the early stages of making a picture , silver halides are converted to black metallic silver . One of the basic methods of making a film more sensitive to light is to use larger grains , and this naturally affects the quality of the image .
In fact , the speckled texture of ' graininess ' is not the individual grains , but clumps of them overlapping each other in the emulsion . To the eye , however , the explanation does not matter ; the fact remains that graininess intrudes on the image . Now , whether this appears to spoil the image or not is entirely a matter of taste , just as some painters try to avoid brushmarks and the thickness of the paint from being obvious , while others use the textures to help the picture . On balance , most photographers aim for a grain - free result ; using grain when you want it is fine , but having it unavoidably is annoying .
Film speed is measured in standard units designated by the initials ISO International Standards Organisation ) . Strictly speaking , the number is in two parts , equivalent to the old ASA and DIN ratings , and looks like this : ISO 25/15 . In normal use , however , the last figure , which is the DIN equivalent , is usually dropped . Although films could be made in any speed between single digits and over ISO 1000 , in practice the film manufacturers group them . The speed groups are slow , between ISO 25 and ISO 50 ; medium , between ISO 64 and ISO 100 ; fast , between ISO 200 and ISO 400 ; and ultra - fast , over ISO 640 . Within these groups , there is a choice of brands , most of them very similar in performance in the very competitive film market .
Photographers ' tolerance of graininess varies , and one of the main factors is the degree of enlargement . There is little point worrying about it if the prints you make are all postcard - sized . If they are larger graininess begins to show , particularly on fast films , and larger prints will show it even more .
ABOVE Slow films ( ISO 100 and under ) are perfectly suited to still life work , where a photograph's ability to show detail is all - important .
LEFT As a general rule , slower films display richer , more vibrant colours than their faster counterparts , and will always give sharper results .
LEFT While an increase in grain is an unavoidable consequence of using fast films , the photographer who produces small prints may not find the trait a problem .
BELOW With faster films , the larger the print , the more noticeable the grain . At 10x8in , graininess begins to show , and larger prints will show it even more .
SLOW OR FAST ?
Film speed and graininess are inextricably linked . If you choose a fast film because it will be easier to use in low levels of lighting , the image will be more grainy and so show less detail . If a grain - free image is important , you must choose a slow film . The reason for this is that , like basic black - and - white film , colour emulsions rely on silver grains to form the image . During the processing , these are replaced by coloured dyes , but in the early stages of making a picture , silver halides are converted to black metallic silver . One of the basic methods of making a film more sensitive to light is to use larger grains , and this naturally affects the quality of the image .
In fact , the speckled texture of ' graininess ' is not the individual grains , but clumps of them overlapping each other in the emulsion . To the eye , however , the explanation does not matter ; the fact remains that graininess intrudes on the image . Now , whether this appears to spoil the image or not is entirely a matter of taste , just as some painters try to avoid brushmarks and the thickness of the paint from being obvious , while others use the textures to help the picture . On balance , most photographers aim for a grain - free result ; using grain when you want it is fine , but having it unavoidably is annoying .
Film speed is measured in standard units designated by the initials ISO International Standards Organisation ) . Strictly speaking , the number is in two parts , equivalent to the old ASA and DIN ratings , and looks like this : ISO 25/15 . In normal use , however , the last figure , which is the DIN equivalent , is usually dropped . Although films could be made in any speed between single digits and over ISO 1000 , in practice the film manufacturers group them . The speed groups are slow , between ISO 25 and ISO 50 ; medium , between ISO 64 and ISO 100 ; fast , between ISO 200 and ISO 400 ; and ultra - fast , over ISO 640 . Within these groups , there is a choice of brands , most of them very similar in performance in the very competitive film market .
Photographers ' tolerance of graininess varies , and one of the main factors is the degree of enlargement . There is little point worrying about it if the prints you make are all postcard - sized . If they are larger graininess begins to show , particularly on fast films , and larger prints will show it even more .
ABOVE Slow films ( ISO 100 and under ) are perfectly suited to still life work , where a photograph's ability to show detail is all - important .
LEFT As a general rule , slower films display richer , more vibrant colours than their faster counterparts , and will always give sharper results .
LEFT While an increase in grain is an unavoidable consequence of using fast films , the photographer who produces small prints may not find the trait a problem .
BELOW With faster films , the larger the print , the more noticeable the grain . At 10x8in , graininess begins to show , and larger prints will show it even more .
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