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تحديد وقت التعريض .. المعالجة والطباعة بالأبيض والأسود .. المرشد خطوة بخطوة للتصوير الفوتوغرافي
Selecting the exposure time
Before making an enlargement , you must choose an exposure time that will produce the best results from your negative . Do this by making different exposures in separate bands on a single strip of normal grade bromide paper ; from this test strip you can quickly judge how the image will look at those exposure times .
Make the test strip a reasonable size , say half a sheet of paper , or a third each exposure band need only occupy a small area . Ideally the strip should be positioned on the baseboard so that every band will be representative of the whole image : try to include a cross - section of the light and dark parts of the picture in each band , and avoid having all shadow in one all highlights in another . Having taken a range of exposures around an estimated time such as 3 , 6 , 12 , and 24 secs for an estimated correct exposure time 10 secs ) develop the print fully and , after fixing for a minute or so , switch on the white light and check your results . You can now decide which time will give the print you want . You may well decide that the best exposure time for the final print falls midway between two of the test bands , in which case choose a time half way between the two times . Final- ly , take a complete sheet of paper and expose it for the time you have selected ; then process it to produce your enlarged print . When it is dry , you can assess the quality of the print , as shown opposite , and check for any errors in enlarging and processing .
Making a test strip
1. Adjust the focus until the image is absolutely sharp . As focusing also affects size , you may have to readjust the en- larger head .
2. Use a smaller aperture , say f8 or f11 , for light negatives than i for dark ones . This will prevent excessively long or short exposure times .
3. Swing over the red filter and tear or cut a strip of normal grade bromide paper large en- ough to get a representative range of exposure times .
4. Insert the paper strip under the masking easel , shiny side up . and position it so each exposure band will include both light and dark parts of the image .
5. Remove the red filter and expose the whole paper strip for 3 seconds .
6. Using a piece of card , cover one quarter of the paper strip and expose the remainder for another 3 seconds .
7. Cover half , and then three quarters of the strip , giving additional 6 and 12 second exposures respectively .
8. Process the test strip follow- ing the same procedure you used for a full sheet , as shown on page 76 .
The test strip
Range the exposures on the test strip around the estimated expo- sure time for the negative ( in this case 10 seconds ) . The most satis factory result in this example ap- pears in the band which received a total of 12 seconds exposure : other bands appear too dark or too light .
If your whole strip is too dark . or too light , make another test strip with increased , or decreased , exposure times . It may be helpful to close or open the lens aperture by one stop this will give the exact equivalent of half or double the exposure time . Each time you change your negative or alter the size of the enlargement you should make another test strip .
Making the enlargement
1. Under safelighting , place a sheet of bromide paper squarely under the masking strips of the easel .
2. Check that the red filter is out of the way . Now switch on the enlarger for the time given by your test strip ( in this case 12 seconds ) .
3. When the time is complete . carefully remove the paper and follow processing procedure for the print , described on page 76 .
Assessing the final print
Lighting
Check for even illumination across the print . In this picture the lighting direction is from right to left , but because of the reflective surroundings there is no detect- able fall - off in illumination . Some times less exposure ( by " shading " . see p . 86 ) is needed for one side of a print than the other , to com- pensate for uneven lighting .
Highlights
The lightest important detail areas on the print should not appear " washed out , or grayed over- the forehead here shows a gradu- ated tone , giving roundness of form . There should just be a tone difference between the skin and the whiteness of eyes and teeth . These highlights should almost be as white as the picture borders .
Shadows
Print blacks should be a rich black , to give the image body and " depth " . But try not to let darkest important detail turn into solid . featureless black paper - there is still just enough hair detail here to give shape to the top of the man's head .
Tone range
There should be a wide range of gray tones between lightest high- light and darkest shadow . This gives a natural . three dimensional appearance . Excessive grays give a very " flat " appearance , while too few have a harsh effect . You can adjust contrast by printing on a different paper grade , as ex- plained on pages 84-5 .
Selecting the exposure time
Before making an enlargement , you must choose an exposure time that will produce the best results from your negative . Do this by making different exposures in separate bands on a single strip of normal grade bromide paper ; from this test strip you can quickly judge how the image will look at those exposure times .
Make the test strip a reasonable size , say half a sheet of paper , or a third each exposure band need only occupy a small area . Ideally the strip should be positioned on the baseboard so that every band will be representative of the whole image : try to include a cross - section of the light and dark parts of the picture in each band , and avoid having all shadow in one all highlights in another . Having taken a range of exposures around an estimated time such as 3 , 6 , 12 , and 24 secs for an estimated correct exposure time 10 secs ) develop the print fully and , after fixing for a minute or so , switch on the white light and check your results . You can now decide which time will give the print you want . You may well decide that the best exposure time for the final print falls midway between two of the test bands , in which case choose a time half way between the two times . Final- ly , take a complete sheet of paper and expose it for the time you have selected ; then process it to produce your enlarged print . When it is dry , you can assess the quality of the print , as shown opposite , and check for any errors in enlarging and processing .
Making a test strip
1. Adjust the focus until the image is absolutely sharp . As focusing also affects size , you may have to readjust the en- larger head .
2. Use a smaller aperture , say f8 or f11 , for light negatives than i for dark ones . This will prevent excessively long or short exposure times .
3. Swing over the red filter and tear or cut a strip of normal grade bromide paper large en- ough to get a representative range of exposure times .
4. Insert the paper strip under the masking easel , shiny side up . and position it so each exposure band will include both light and dark parts of the image .
5. Remove the red filter and expose the whole paper strip for 3 seconds .
6. Using a piece of card , cover one quarter of the paper strip and expose the remainder for another 3 seconds .
7. Cover half , and then three quarters of the strip , giving additional 6 and 12 second exposures respectively .
8. Process the test strip follow- ing the same procedure you used for a full sheet , as shown on page 76 .
The test strip
Range the exposures on the test strip around the estimated expo- sure time for the negative ( in this case 10 seconds ) . The most satis factory result in this example ap- pears in the band which received a total of 12 seconds exposure : other bands appear too dark or too light .
If your whole strip is too dark . or too light , make another test strip with increased , or decreased , exposure times . It may be helpful to close or open the lens aperture by one stop this will give the exact equivalent of half or double the exposure time . Each time you change your negative or alter the size of the enlargement you should make another test strip .
Making the enlargement
1. Under safelighting , place a sheet of bromide paper squarely under the masking strips of the easel .
2. Check that the red filter is out of the way . Now switch on the enlarger for the time given by your test strip ( in this case 12 seconds ) .
3. When the time is complete . carefully remove the paper and follow processing procedure for the print , described on page 76 .
Assessing the final print
Lighting
Check for even illumination across the print . In this picture the lighting direction is from right to left , but because of the reflective surroundings there is no detect- able fall - off in illumination . Some times less exposure ( by " shading " . see p . 86 ) is needed for one side of a print than the other , to com- pensate for uneven lighting .
Highlights
The lightest important detail areas on the print should not appear " washed out , or grayed over- the forehead here shows a gradu- ated tone , giving roundness of form . There should just be a tone difference between the skin and the whiteness of eyes and teeth . These highlights should almost be as white as the picture borders .
Shadows
Print blacks should be a rich black , to give the image body and " depth " . But try not to let darkest important detail turn into solid . featureless black paper - there is still just enough hair detail here to give shape to the top of the man's head .
Tone range
There should be a wide range of gray tones between lightest high- light and darkest shadow . This gives a natural . three dimensional appearance . Excessive grays give a very " flat " appearance , while too few have a harsh effect . You can adjust contrast by printing on a different paper grade , as ex- plained on pages 84-5 .
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