تويت
التصوير الفوتوغرافي الحديث
تحديد الوضع الصحيح ..
استخدام عداد التعرض ..
USING THE EXPOSURE METER
All exposure meters have a dial or pointer which must first be set for the speed of the film being used . Generally speaking , this will be the ASA speed rating . Once this has been done , you can rely on the readings from the meter .
Some meters enable you to read the exposure settings directly from the meter needle - in others you must turn a calculator dial . Some meters will give you a direct reading in Exposure Values ( EV ) . If your camera uses the EV system , you need not concern yourself with f / numbers or shutter speeds .
THE QUICK AND EASY METHOD
In this method you simply aim the meter at the subject to get an average overall reading as in Figure 8 . Here you must rely on the exposure latitude of the film to take care of the shadows as well as the highlights . This method . works well for ordinary outdoor shots where the lighting is reasonably uniform and shadow detail is not important . When taking your reading , be careful not to let any part of the meter case , your fingers , or the neck cord get in front of the photocell . If the scene includes some sky , aim the meter downward slightly to limit the amount of sky included in the meter's angle of view . If you fail to do this , the reading will be too high because of the strong light coming from the sky , and your pictures will be underexposed .
Fig . 8 Hold exposure meter so that photocell is aimed directly at subject
After the reading has been taken , read the exposure setting and then select the best combination of shutter speed and f / numbers for the exposure indicated on your meter .
THE CLOSE - UP METHOD
This method should be used for portraits or any picture which contains one main object of interest . Hold the meter about six inches from the subject . If the subject is smaller than six inches , move in until the meter is no farther away from the subject than the subject's largest dimension . In other words , if you are taking a close - up of an object that is three inches across , the meter ought to be held no more than three inches away .
Aim the meter very carefully at the subject to be sure the reading is of the subject and not the surrounding area . Take care that the meter does not cast a shadow on the subject . If it does , move the meter slightly until the shadow is eliminated , but tilt the meter to keep it aimed toward the subject .
If you can't get to the subject for a close - up reading , take a reading from objects similar to the subject that are in the same light . Read nearby trees for trees in the scene , nearby rocks for distant rocks , etc. A favorite and convenient substitute for a subject's face is the palm of your hand ( Figure 9 ) . When taking a close - up reading , remember the meter is calibrated to give correct exposure for average subjects . Flesh tones are about twice as bright as this average , so if you take your meter reading from a face or a hand , you will get a higher reading
than is correct . To compensate for this high reading , double the exposure ( open up one f / stop ) . For example , if the reading from a subject's face indicates an exposure of 1 / 125th second at f / 11 , expose for 1 / 125th second at f / 8 . Some meters have an additional arrow or pointer to give you the correct reading for flesh tones without requiring you to do any mental arithmetic . In Figure 10 , the people on the sailboat are too far away to permit exposure readings to be taken of them . This is the type of subject where exposure readings can be taken from your hand .
Fig . 9 Reading palm of hand as : substitute for sub ject . Palm must receive same lighting as subject , and meter must not cast a shadow on palm .
Fig . 10 Type of subject in which meter reading can be taken of the palm .
THE STANDARD GRAY CARD
Exposure meters are calibrated by their manufacturers to give a reading based on the average reflectivity of the subject . A white sheet of paper may have a reflectivity of 90 % to 95 % , while dull black clothing may have a reflectivity of 5 % or so . The industry has set a value of 18 % as its standard of average reflectivity . You can obtain from your photographic dealer a standard gray card having this 18 % reflectivity . Use it as your standard while photographing small objects in close - up when you cannot be sure of getting the correct reading and the lighting is very spotty .
To use such a gray card , simply put it in front of your subject and take a reading from it , making sure that it receives exactly the same illumination as the subject itself . Then use the exposure reading you get from the gray card .
THE BRIGHTNESS RANGE METHOD
This is the most accurate method of determining exposure for scenes in which there is a wide range of brightness from deep shadows to brightly illuminated highlights . As you may recall , black - and - white film has considerable latitude of exposure . With most This is equivalent to seven f / stops . To put this another way , everything in a scene can be correctly exposed with black - and - white film if the highlights are no more than 128 times as bright as the shadows .
In actual practice , this range can be extended because it is seldom necessary to get perfect exposure for either the extreme shadows or highlights . The deepest shadows can usually be permitted to go completely black because there is seldom anything of interest in them . The extreme highlights , such as clouds or the glint of sun as it is reflected from water , can go completely white without any serious loss of picture quality . Therefore , if an exposure is chosen which takes in all the important detail within this 128 to 1 ratio , all important tones in the picture will be properly reproduced .
To use the brightness range method , simply take a close - up reading of the darkest area in which you want detail and another reading of the lightest area in which you want detail .
Some exposure meters have arrows on each side of the main exposure indicator to indicate the 128 to I ( seven f / stops ) range . In such meters , one of these arrows is labeled U ( for underexposure ) , and the other labeled O ( for overexposure ) . Set the U arrow at the reading from the shadow area . If the highlight reading is not beyond O , the entire brightness range of the scene is within the film exposure latitude and you will get properly exposed picture if I you give the exposure indicated by the main arrow . However , if the highlight reading falls beyond O , it will be overexposed . In that case you must make up your mind whether to slight the shadows or the highlights , since you cannot have detail in both . Possibly the shadow you select isn't too important after all , so take another reading of a shadow that is not quite so deep and see if that permits you to keep the overall brightness within the seven f / stop range . On the other hand , perhaps the highlight you read is the side of a white picket fence which has no detail to be recorded anyhow ; select another in which there is some detail but which is not quite so bright . When you have finally worked down the brightness range to within the seven f / stops by sacrificing unimportant areas in either the shadows or highlights , the correct exposure will be indicated by the main exposure arrow .
If your exposure meter does not have the O and U arrows , you can still use this method . Simply scratch or write a line four full stops below the main arrow and label it U. Similarly , scratch an O arrow three stops above the main arrow . This gives a range of seven full stops from U to 0 .
The brightness range method may also be used for positive color film , such as Kodachrome , Ektachrome , Anscochrome , Agfachrome , etc. , but the U and O arrows represent much too wide a range because of the more limited exposure latitude of positive color films . Consider the U position to be two stops below and the O position to be two stops above the main arrow , and you will get good . results provided you disregard all deep shadows and strong highlights . Positive color film will not reproduce accurate colors in either area anyhow , so restrict your readings accordingly . Negative color films , such as Kodacolor or Ektacolor , have exposure latitudes coming close to that of black - and - white film . For best results , consider the U arrow as three stops below the normal arrow , and the O arrow as two stops above the normal arrow . This is a safe latitude range - you can actually extend this range to the full seven stops used for black - and - white film and still get reasonably good pictures .
تحديد الوضع الصحيح ..
استخدام عداد التعرض ..
USING THE EXPOSURE METER
All exposure meters have a dial or pointer which must first be set for the speed of the film being used . Generally speaking , this will be the ASA speed rating . Once this has been done , you can rely on the readings from the meter .
Some meters enable you to read the exposure settings directly from the meter needle - in others you must turn a calculator dial . Some meters will give you a direct reading in Exposure Values ( EV ) . If your camera uses the EV system , you need not concern yourself with f / numbers or shutter speeds .
THE QUICK AND EASY METHOD
In this method you simply aim the meter at the subject to get an average overall reading as in Figure 8 . Here you must rely on the exposure latitude of the film to take care of the shadows as well as the highlights . This method . works well for ordinary outdoor shots where the lighting is reasonably uniform and shadow detail is not important . When taking your reading , be careful not to let any part of the meter case , your fingers , or the neck cord get in front of the photocell . If the scene includes some sky , aim the meter downward slightly to limit the amount of sky included in the meter's angle of view . If you fail to do this , the reading will be too high because of the strong light coming from the sky , and your pictures will be underexposed .
Fig . 8 Hold exposure meter so that photocell is aimed directly at subject
After the reading has been taken , read the exposure setting and then select the best combination of shutter speed and f / numbers for the exposure indicated on your meter .
THE CLOSE - UP METHOD
This method should be used for portraits or any picture which contains one main object of interest . Hold the meter about six inches from the subject . If the subject is smaller than six inches , move in until the meter is no farther away from the subject than the subject's largest dimension . In other words , if you are taking a close - up of an object that is three inches across , the meter ought to be held no more than three inches away .
Aim the meter very carefully at the subject to be sure the reading is of the subject and not the surrounding area . Take care that the meter does not cast a shadow on the subject . If it does , move the meter slightly until the shadow is eliminated , but tilt the meter to keep it aimed toward the subject .
If you can't get to the subject for a close - up reading , take a reading from objects similar to the subject that are in the same light . Read nearby trees for trees in the scene , nearby rocks for distant rocks , etc. A favorite and convenient substitute for a subject's face is the palm of your hand ( Figure 9 ) . When taking a close - up reading , remember the meter is calibrated to give correct exposure for average subjects . Flesh tones are about twice as bright as this average , so if you take your meter reading from a face or a hand , you will get a higher reading
than is correct . To compensate for this high reading , double the exposure ( open up one f / stop ) . For example , if the reading from a subject's face indicates an exposure of 1 / 125th second at f / 11 , expose for 1 / 125th second at f / 8 . Some meters have an additional arrow or pointer to give you the correct reading for flesh tones without requiring you to do any mental arithmetic . In Figure 10 , the people on the sailboat are too far away to permit exposure readings to be taken of them . This is the type of subject where exposure readings can be taken from your hand .
Fig . 9 Reading palm of hand as : substitute for sub ject . Palm must receive same lighting as subject , and meter must not cast a shadow on palm .
Fig . 10 Type of subject in which meter reading can be taken of the palm .
THE STANDARD GRAY CARD
Exposure meters are calibrated by their manufacturers to give a reading based on the average reflectivity of the subject . A white sheet of paper may have a reflectivity of 90 % to 95 % , while dull black clothing may have a reflectivity of 5 % or so . The industry has set a value of 18 % as its standard of average reflectivity . You can obtain from your photographic dealer a standard gray card having this 18 % reflectivity . Use it as your standard while photographing small objects in close - up when you cannot be sure of getting the correct reading and the lighting is very spotty .
To use such a gray card , simply put it in front of your subject and take a reading from it , making sure that it receives exactly the same illumination as the subject itself . Then use the exposure reading you get from the gray card .
THE BRIGHTNESS RANGE METHOD
This is the most accurate method of determining exposure for scenes in which there is a wide range of brightness from deep shadows to brightly illuminated highlights . As you may recall , black - and - white film has considerable latitude of exposure . With most This is equivalent to seven f / stops . To put this another way , everything in a scene can be correctly exposed with black - and - white film if the highlights are no more than 128 times as bright as the shadows .
In actual practice , this range can be extended because it is seldom necessary to get perfect exposure for either the extreme shadows or highlights . The deepest shadows can usually be permitted to go completely black because there is seldom anything of interest in them . The extreme highlights , such as clouds or the glint of sun as it is reflected from water , can go completely white without any serious loss of picture quality . Therefore , if an exposure is chosen which takes in all the important detail within this 128 to 1 ratio , all important tones in the picture will be properly reproduced .
To use the brightness range method , simply take a close - up reading of the darkest area in which you want detail and another reading of the lightest area in which you want detail .
Some exposure meters have arrows on each side of the main exposure indicator to indicate the 128 to I ( seven f / stops ) range . In such meters , one of these arrows is labeled U ( for underexposure ) , and the other labeled O ( for overexposure ) . Set the U arrow at the reading from the shadow area . If the highlight reading is not beyond O , the entire brightness range of the scene is within the film exposure latitude and you will get properly exposed picture if I you give the exposure indicated by the main arrow . However , if the highlight reading falls beyond O , it will be overexposed . In that case you must make up your mind whether to slight the shadows or the highlights , since you cannot have detail in both . Possibly the shadow you select isn't too important after all , so take another reading of a shadow that is not quite so deep and see if that permits you to keep the overall brightness within the seven f / stop range . On the other hand , perhaps the highlight you read is the side of a white picket fence which has no detail to be recorded anyhow ; select another in which there is some detail but which is not quite so bright . When you have finally worked down the brightness range to within the seven f / stops by sacrificing unimportant areas in either the shadows or highlights , the correct exposure will be indicated by the main exposure arrow .
If your exposure meter does not have the O and U arrows , you can still use this method . Simply scratch or write a line four full stops below the main arrow and label it U. Similarly , scratch an O arrow three stops above the main arrow . This gives a range of seven full stops from U to 0 .
The brightness range method may also be used for positive color film , such as Kodachrome , Ektachrome , Anscochrome , Agfachrome , etc. , but the U and O arrows represent much too wide a range because of the more limited exposure latitude of positive color films . Consider the U position to be two stops below and the O position to be two stops above the main arrow , and you will get good . results provided you disregard all deep shadows and strong highlights . Positive color film will not reproduce accurate colors in either area anyhow , so restrict your readings accordingly . Negative color films , such as Kodacolor or Ektacolor , have exposure latitudes coming close to that of black - and - white film . For best results , consider the U arrow as three stops below the normal arrow , and the O arrow as two stops above the normal arrow . This is a safe latitude range - you can actually extend this range to the full seven stops used for black - and - white film and still get reasonably good pictures .
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