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أخطاء الطباعة .. المعالجة والطباعة بالأبيض والأسود .. المرشد خطوة بخطوة للتصوير الفوتوغرافي
Printing errors
If you are not satisfied with your print , you may at first be unable to identify the nature of the fault . Begin your analysis by care- fully comparing print and negative . Often faults such as poor tone , marks , and un- sharpness can be due to these same errors in the negative . But if the negative seems fine there are other possible causes .
Wrong density or contrast
A print which appears too light or too dark has probably had the wrong printing expo- sure . If , for example , highlight details in the negative come up blank on the print , in- crease the exposure time , either overall or just for this part of the print ( " printing - in " ) . Equally , areas of detail that are too dark and lost on the print can be improved by " dodg- ing " during exposure Printing - in and dodg- ing are explained on page 86 .
Excessive contrast ( too few gray tones between black and white ) is probably due to using too hard a paper grade . Low con- trast ( flat , gray appearance ) results if the paper is too soft , or the print under- developed . Check development time , and the temperature , dilution , and age of your developer . If the print seems grayish , with little contrast , you may have dust , con- densation , or marks on the enlarging lens .
An unsafe safelight or badly blacked - out darkroom will also reduce print contrast by " fogging " minutely tinting the whites gray . You can check for this by comparing the white back of the paper with the bright- est image highlights . Other causes of fog ( often giving a yellowish stain too ) are over- development , or lifting the print from the developer too frequently to check the image .
Marks and stains
- The usual cause of gray , yellow , or purplish patches is insufficient fixing . Sometimes re- fixing the print can remove these stains . Black lines on the print often quite short and in groups are created if the emulsion surface is grazed . A print with concentric white or gray rings ( Newton's Rings ) results when the two glass surfaces of the negative carrier are not in complete contact .
Unsharpness
Always check the sharpness of the grain ( see p . 38 ) on the print first ; if this is sharp any unsharpness of the final image must exist on the negative . If the print grain is unsharp , but the negative is sharp , then the fault must have arisen during enlargement . Perhaps the enlarger shifted position or was jarred during exposure , the negative may have buckled in the carrier , or the image was focused through the red safe filter . Images which lack strong shapes are quite difficult to focus in the enlarger , particularly if the negative is also dense . In such cases , switch out the safelight and use a focus magnifier to focus the grain pattern itself .
Checking against the test strip
Underexposing the print , giving the shortest exposure time on the test strip , below , results in a weak , pale image , right . Over - exposure , has the opposite effect , below right , giving a dark print with blackened shadows , even though highlights may show detail . If your results are still too light or too dark , even after quite long or short exposure times , you should adjust the lens aperture each click stop doubles or halves image brightness .
Spread shadows
Dust , grease , or condensation on the enlarger lens will diffuse and scatter light during exposure . Since light causes printing paper to darken , the resulting print appears slightly smudgy with shadow areas " spread " , right . Check the lens by looking up through it with the enlarger switched on . If the glass seems misty , clean the top and bottom surfaces with a soft brush or cleaning tissue . One of the biggest enemies in the darkroom is dust , and it is always advisable to cover equipment such as the enlarger when it is not in use .
Abrasion of paper
Although printing paper emulsion is generally tougher than film it is quite easily marked . It does not need to be handled by its edges , but scraping it over a rough sur- face or catching it with your finger nail creates black scratch marks , as shown right . Similarly , you can mark the print by rough handling with tongs in the devel- oper . A really severe gouge may even scrape some of the emulsion off , leaving a white mark . Handle paper carefully and do not , for example , move it face down across a bench surface or box edge .
Contamination marks
Contamination marks are caused by handling dry paper with damp fingers , and by splashes of fixer solution . Keep the dry and wet darkroom areas separate , and always dry your hands before touching dry printing paper .
Fogged paper
Accidental fogging shows mostly in the highlights and white bor- ders of the print , as a slight gray veiling . The usual cause is a safe- light which is either too bright , too close , or not the right color .
Patchiness
Uneven illumination of the nega tive or debris on the top surface of the condenser causes patchiness on the print . Often this cannot be detected when focusing the image at a wide aperture .
Image shake
Blurring or double image is usual- ly caused by jolting the enlarger or knocking the baseboard during exposure . However , sometimes a worn enlarger will slip or shift slightly on its column and blur the image .
Using cropping to correct framing errors
One of the advantages of printing your own negatives is that you can enlarge selected parts of your pictures to cut out unwanted detail , alter the proportions and even change from a vertical to a horizontal format by cropping the image . By turning the masking easel on the baseboard of your enlarger you can correct sloping horizontal and vertical lines origi- nally caused by not holding the camera straight .
For example , the print above could be greatly improved by restricting the enlarged print to the center area to cut out the distracting figure , right , and mov- ing the easel to straighten the horizon . The limiting factors to enlarging only a part of the neg- ative are the increase in size of the film grain and the decrease in image sharpness .
Reminders : printing and enlarging
Always take care of your negatives
Unlike prints they cannot be replaced ; hold them by their edges and protect them from dirt , liquids etc .
Photographic printing paper is sensitive to white light
Always keep it in its light- proof container ; make sure you replace it before chang- ing to normal lighting .
Keep the developer at around 68 ° F ( 20 ° C ) in temperature
If necessary , put the developer tray inside another , larger tray to maintain this temperature .
Always give the correct development time
Adjust your results through exposure not development .
When making a contact print , the emulsion sides of the film and the paper should be in contact
The emulsion side of film and paper is that toward which they curl ; it is dull for film and shiny for paper .
Cleanliness in the darkroom is essential
Dust or grit , particularly in the enlarger , can ruin your work .
Always make a test strip of each print
Assess the strip and choose the exposure time before printing and changing to the next negative . Too much haste can waste time and expensive materials .
After enlarging , assess your print Enlarging makes the most of your pictures but it will also show up faults which may be remedied .
Printing errors
If you are not satisfied with your print , you may at first be unable to identify the nature of the fault . Begin your analysis by care- fully comparing print and negative . Often faults such as poor tone , marks , and un- sharpness can be due to these same errors in the negative . But if the negative seems fine there are other possible causes .
Wrong density or contrast
A print which appears too light or too dark has probably had the wrong printing expo- sure . If , for example , highlight details in the negative come up blank on the print , in- crease the exposure time , either overall or just for this part of the print ( " printing - in " ) . Equally , areas of detail that are too dark and lost on the print can be improved by " dodg- ing " during exposure Printing - in and dodg- ing are explained on page 86 .
Excessive contrast ( too few gray tones between black and white ) is probably due to using too hard a paper grade . Low con- trast ( flat , gray appearance ) results if the paper is too soft , or the print under- developed . Check development time , and the temperature , dilution , and age of your developer . If the print seems grayish , with little contrast , you may have dust , con- densation , or marks on the enlarging lens .
An unsafe safelight or badly blacked - out darkroom will also reduce print contrast by " fogging " minutely tinting the whites gray . You can check for this by comparing the white back of the paper with the bright- est image highlights . Other causes of fog ( often giving a yellowish stain too ) are over- development , or lifting the print from the developer too frequently to check the image .
Marks and stains
- The usual cause of gray , yellow , or purplish patches is insufficient fixing . Sometimes re- fixing the print can remove these stains . Black lines on the print often quite short and in groups are created if the emulsion surface is grazed . A print with concentric white or gray rings ( Newton's Rings ) results when the two glass surfaces of the negative carrier are not in complete contact .
Unsharpness
Always check the sharpness of the grain ( see p . 38 ) on the print first ; if this is sharp any unsharpness of the final image must exist on the negative . If the print grain is unsharp , but the negative is sharp , then the fault must have arisen during enlargement . Perhaps the enlarger shifted position or was jarred during exposure , the negative may have buckled in the carrier , or the image was focused through the red safe filter . Images which lack strong shapes are quite difficult to focus in the enlarger , particularly if the negative is also dense . In such cases , switch out the safelight and use a focus magnifier to focus the grain pattern itself .
Checking against the test strip
Underexposing the print , giving the shortest exposure time on the test strip , below , results in a weak , pale image , right . Over - exposure , has the opposite effect , below right , giving a dark print with blackened shadows , even though highlights may show detail . If your results are still too light or too dark , even after quite long or short exposure times , you should adjust the lens aperture each click stop doubles or halves image brightness .
Spread shadows
Dust , grease , or condensation on the enlarger lens will diffuse and scatter light during exposure . Since light causes printing paper to darken , the resulting print appears slightly smudgy with shadow areas " spread " , right . Check the lens by looking up through it with the enlarger switched on . If the glass seems misty , clean the top and bottom surfaces with a soft brush or cleaning tissue . One of the biggest enemies in the darkroom is dust , and it is always advisable to cover equipment such as the enlarger when it is not in use .
Abrasion of paper
Although printing paper emulsion is generally tougher than film it is quite easily marked . It does not need to be handled by its edges , but scraping it over a rough sur- face or catching it with your finger nail creates black scratch marks , as shown right . Similarly , you can mark the print by rough handling with tongs in the devel- oper . A really severe gouge may even scrape some of the emulsion off , leaving a white mark . Handle paper carefully and do not , for example , move it face down across a bench surface or box edge .
Contamination marks
Contamination marks are caused by handling dry paper with damp fingers , and by splashes of fixer solution . Keep the dry and wet darkroom areas separate , and always dry your hands before touching dry printing paper .
Fogged paper
Accidental fogging shows mostly in the highlights and white bor- ders of the print , as a slight gray veiling . The usual cause is a safe- light which is either too bright , too close , or not the right color .
Patchiness
Uneven illumination of the nega tive or debris on the top surface of the condenser causes patchiness on the print . Often this cannot be detected when focusing the image at a wide aperture .
Image shake
Blurring or double image is usual- ly caused by jolting the enlarger or knocking the baseboard during exposure . However , sometimes a worn enlarger will slip or shift slightly on its column and blur the image .
Using cropping to correct framing errors
One of the advantages of printing your own negatives is that you can enlarge selected parts of your pictures to cut out unwanted detail , alter the proportions and even change from a vertical to a horizontal format by cropping the image . By turning the masking easel on the baseboard of your enlarger you can correct sloping horizontal and vertical lines origi- nally caused by not holding the camera straight .
For example , the print above could be greatly improved by restricting the enlarged print to the center area to cut out the distracting figure , right , and mov- ing the easel to straighten the horizon . The limiting factors to enlarging only a part of the neg- ative are the increase in size of the film grain and the decrease in image sharpness .
Reminders : printing and enlarging
Always take care of your negatives
Unlike prints they cannot be replaced ; hold them by their edges and protect them from dirt , liquids etc .
Photographic printing paper is sensitive to white light
Always keep it in its light- proof container ; make sure you replace it before chang- ing to normal lighting .
Keep the developer at around 68 ° F ( 20 ° C ) in temperature
If necessary , put the developer tray inside another , larger tray to maintain this temperature .
Always give the correct development time
Adjust your results through exposure not development .
When making a contact print , the emulsion sides of the film and the paper should be in contact
The emulsion side of film and paper is that toward which they curl ; it is dull for film and shiny for paper .
Cleanliness in the darkroom is essential
Dust or grit , particularly in the enlarger , can ruin your work .
Always make a test strip of each print
Assess the strip and choose the exposure time before printing and changing to the next negative . Too much haste can waste time and expensive materials .
After enlarging , assess your print Enlarging makes the most of your pictures but it will also show up faults which may be remedied .
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