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الأضواء الموجودة .. مصدر الضوء .. كيفية التقاط وتطوير الصور بالأبيض والأسود
EXISTING LIGHTS
Existing light is generally taken to mean illumination that is artificial but not intended for photography . As we have already seen , film , lens aperture and shutter speed are all built around a normal standard that is geared to outdoor daylight , and even though this varies over a range of several stops , it is still an entire level apart from the much weaker lighting found in interiors and , of course , at night .
There are particular problems in photographing by existing light . Principally , they are a low level of illumination , which limits the kind of photography that is possible , and high contrast caused by the unevenness . The colour balance of existing artificial light is also often unusual , but fortunately this is no concern for black - and - white photography .
FOCUSING AND FRAMING
The first obvious problem at night and in dark interiors is that it is simply not easy to see what you are doing . As far as the camera controls are concerned , some makes have built - in illumination - either LEDs or a small lamp that is activated by a special button to light up the now more usual LCD . In any case , however , pocket torch or flashlight is an essential piece of equipment .
Composing and focusing the image is difficult with a single lens reflex , as the mirror and focusing screen together absorb a considerable amount of light . This is not so obvious in bright daylight , but in low light conditions the image is likely to fall below a workable level . If you can replace the focusing screen easily , a full microprism grid is an answer : microprisms absorb less light than the ground area of the glass . Otherwise , you may have to rely on a distance scale engraved on the lens . Rangefinder cameras score heavily in low lighting : the straight - through optical viewfinder is almost as bright as a direct view . One tip : in either case , use points of light for focusing . Wide - angle lenses have greater depth of field and so need less critical focusing ; equally , however , they are expected to give sharply focused images , so that gross focusing errors are particularly obvious .
BELOW Shooting in low light levels can bring focusing problems . One solution is to use points of light in a scene , such as the lamps here , to focus upon .
OPPOSITE Another solution to the focusing problem is to exploit the added depth of field inherent in a wide- angle lens ; because so much of the scene will remain sharp , you have fewer worries about focus being spot on .
EXPOSURE
It may not always be possible to make a useful exposure measurement from the position of the camera , with any kind of meter . A typical problem situation is when the subject of interest is relatively small in the frame , well lit but surroun- ded by a dark setting . This , for instance , would apply to a floodlit building in the middle of a town , seen from a distance .
The first thing , therefore , is to be quite clear about what part of the scene you need to measure . The advice given earlier about exposure readings applies to low light levels as well as those in full daylight . Bearing this in mind , there may still be a problem in registering any reading at all with the meter . Most meters have a fairly modest limit in the order of a few seconds of exposure time , and although they will do for most conditions , it is likely to be insufficient if you are using slow film at night .
Nevertheless , there is a solution : change the film speed rating just for the reading . If , for instance , you are using ISO50 film and cannot get a reading even at full aperture and with the slowest shutter speed on the dial , simply turn the film speed selector up until a reading appears . Note the new ISO setting and increase the exposure accordingly . In this example , say that the speed selector needed to be turned as far as ISO200 before a correct reading was shown ; this is 2 stops faster than the film speed in use , so the exposure time would have to be multiplied by four . Remember to reset the shutter speed selector back to the ISO value of the film afterwards . There is also likely to be some reciprocity law failure at speeds of several seconds - use the table below for compensation .
STEADYING THE CAMERA
In low light , slow shutter speeds are normal . To an extent , you can improve your ability to shoot at slow speeds without extra support by practice and by learning how to hold a camera correctly - keep your elbows into your body , breathe out slowly and squeeze the shutter release gently . Even so , always look for any nearby support at a convenient height , such as a low wall or railings . A wide - angle lens allows slower shutter speeds than a telephoto , because things in the viewfinder are magnified less . As a realistic goal , aim to be able to shoot without camera shake at 1 / 30sec with a standard 50mm lens , 1 / 60sec with a 100mm lens , 1 / 125sec with a 200mm , and so on . Nevertheless , as you cannot rely on finding an adequate resting place exactly where you need it , if you are setting out to take night - time pictures , carry a tripod and use a cable release .
BELOW This table suggests exposure adjustments for correcting reciprocity effects with Kodak general- purpose black - and - white films .
Exposure and Development Compensation for Reciprocity Characteristics
KODAK Black - and - White Films .
Information also applies to KODAK PLUS - X Pan Professional and PANATOMIC - X Professional Films .
Basic Camera Handling
With a 35mm SLR in its normal horizontal shooting position , the most stable hold is to support the base of the camera on the heel of the left hand , gripping the right side of the body with the right hand . Press the camera against the face , and keep elbows tucked well in . Wrapping the strap tightly around one wrist also helps to steady the camera . For vertical shooting , a 35mm SLR can be supported either way , depending on personal preference . With a motor- drive fitted , the camera can usually be supported entirely by a right - hand grip .
Where conditions allow , and especially when using a telephoto lens which is particularly prone to the effects of camera shake - make use of all available means of support . These including squatting , kneeling using the camera bag as a rest , and nearby walls .
EXISTING LIGHTS
Existing light is generally taken to mean illumination that is artificial but not intended for photography . As we have already seen , film , lens aperture and shutter speed are all built around a normal standard that is geared to outdoor daylight , and even though this varies over a range of several stops , it is still an entire level apart from the much weaker lighting found in interiors and , of course , at night .
There are particular problems in photographing by existing light . Principally , they are a low level of illumination , which limits the kind of photography that is possible , and high contrast caused by the unevenness . The colour balance of existing artificial light is also often unusual , but fortunately this is no concern for black - and - white photography .
FOCUSING AND FRAMING
The first obvious problem at night and in dark interiors is that it is simply not easy to see what you are doing . As far as the camera controls are concerned , some makes have built - in illumination - either LEDs or a small lamp that is activated by a special button to light up the now more usual LCD . In any case , however , pocket torch or flashlight is an essential piece of equipment .
Composing and focusing the image is difficult with a single lens reflex , as the mirror and focusing screen together absorb a considerable amount of light . This is not so obvious in bright daylight , but in low light conditions the image is likely to fall below a workable level . If you can replace the focusing screen easily , a full microprism grid is an answer : microprisms absorb less light than the ground area of the glass . Otherwise , you may have to rely on a distance scale engraved on the lens . Rangefinder cameras score heavily in low lighting : the straight - through optical viewfinder is almost as bright as a direct view . One tip : in either case , use points of light for focusing . Wide - angle lenses have greater depth of field and so need less critical focusing ; equally , however , they are expected to give sharply focused images , so that gross focusing errors are particularly obvious .
BELOW Shooting in low light levels can bring focusing problems . One solution is to use points of light in a scene , such as the lamps here , to focus upon .
OPPOSITE Another solution to the focusing problem is to exploit the added depth of field inherent in a wide- angle lens ; because so much of the scene will remain sharp , you have fewer worries about focus being spot on .
EXPOSURE
It may not always be possible to make a useful exposure measurement from the position of the camera , with any kind of meter . A typical problem situation is when the subject of interest is relatively small in the frame , well lit but surroun- ded by a dark setting . This , for instance , would apply to a floodlit building in the middle of a town , seen from a distance .
The first thing , therefore , is to be quite clear about what part of the scene you need to measure . The advice given earlier about exposure readings applies to low light levels as well as those in full daylight . Bearing this in mind , there may still be a problem in registering any reading at all with the meter . Most meters have a fairly modest limit in the order of a few seconds of exposure time , and although they will do for most conditions , it is likely to be insufficient if you are using slow film at night .
Nevertheless , there is a solution : change the film speed rating just for the reading . If , for instance , you are using ISO50 film and cannot get a reading even at full aperture and with the slowest shutter speed on the dial , simply turn the film speed selector up until a reading appears . Note the new ISO setting and increase the exposure accordingly . In this example , say that the speed selector needed to be turned as far as ISO200 before a correct reading was shown ; this is 2 stops faster than the film speed in use , so the exposure time would have to be multiplied by four . Remember to reset the shutter speed selector back to the ISO value of the film afterwards . There is also likely to be some reciprocity law failure at speeds of several seconds - use the table below for compensation .
STEADYING THE CAMERA
In low light , slow shutter speeds are normal . To an extent , you can improve your ability to shoot at slow speeds without extra support by practice and by learning how to hold a camera correctly - keep your elbows into your body , breathe out slowly and squeeze the shutter release gently . Even so , always look for any nearby support at a convenient height , such as a low wall or railings . A wide - angle lens allows slower shutter speeds than a telephoto , because things in the viewfinder are magnified less . As a realistic goal , aim to be able to shoot without camera shake at 1 / 30sec with a standard 50mm lens , 1 / 60sec with a 100mm lens , 1 / 125sec with a 200mm , and so on . Nevertheless , as you cannot rely on finding an adequate resting place exactly where you need it , if you are setting out to take night - time pictures , carry a tripod and use a cable release .
BELOW This table suggests exposure adjustments for correcting reciprocity effects with Kodak general- purpose black - and - white films .
Exposure and Development Compensation for Reciprocity Characteristics
KODAK Black - and - White Films .
Information also applies to KODAK PLUS - X Pan Professional and PANATOMIC - X Professional Films .
Basic Camera Handling
With a 35mm SLR in its normal horizontal shooting position , the most stable hold is to support the base of the camera on the heel of the left hand , gripping the right side of the body with the right hand . Press the camera against the face , and keep elbows tucked well in . Wrapping the strap tightly around one wrist also helps to steady the camera . For vertical shooting , a 35mm SLR can be supported either way , depending on personal preference . With a motor- drive fitted , the camera can usually be supported entirely by a right - hand grip .
Where conditions allow , and especially when using a telephoto lens which is particularly prone to the effects of camera shake - make use of all available means of support . These including squatting , kneeling using the camera bag as a rest , and nearby walls .
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