الأضواء الموجودة .. مصدر الضوء .. كيفية التقاط وتطوير الصور بالأبيض والأسود

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  • الأضواء الموجودة .. مصدر الضوء .. كيفية التقاط وتطوير الصور بالأبيض والأسود

    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 .

    اضغط على الصورة لعرض أكبر. 

الإسم:	CamScanner 03-10-2024 12.37_1.jpg 
مشاهدات:	17 
الحجم:	172.8 كيلوبايت 
الهوية:	239531 اضغط على الصورة لعرض أكبر. 

الإسم:	CamScanner 03-10-2024 12.38_1.jpg 
مشاهدات:	11 
الحجم:	237.0 كيلوبايت 
الهوية:	239532 اضغط على الصورة لعرض أكبر. 

الإسم:	CamScanner 03-10-2024 12.39_1.jpg 
مشاهدات:	11 
الحجم:	65.9 كيلوبايت 
الهوية:	239533 اضغط على الصورة لعرض أكبر. 

الإسم:	CamScanner 03-10-2024 12.40_1.jpg 
مشاهدات:	11 
الحجم:	164.9 كيلوبايت 
الهوية:	239534 اضغط على الصورة لعرض أكبر. 

الإسم:	CamScanner 03-10-2024 12.41_1.jpg 
مشاهدات:	11 
الحجم:	138.5 كيلوبايت 
الهوية:	239535

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