تويت
التصوير الفوتوغرافي الحديث
معدات للغرفة المظلمة ..
أجهزة قياس الحرارة ..
قواطع الطباعة ..
توسيع الحامل ..
تطوير الصواني ..
THERMOMETERS
There are quite a number of thermometer styles in use by photographers . The more common are illustrated in Figure 22. The simplest and most accurate is the standard glass - rod type , filled either with colored liquid ( spirit ) or mercury . The spirit thermometer is easier to read and is preferred over mercury , other things being equal . Mercury is not used in the cheaper thermometers , so , as a general rule , the mercury thermometer is likely to be more reliable - unless it is known that the spirit thermom eter is a good one . Neither the mercury nor the spirit ther mometer can change calibra tion , so both will maintain their original accuracy indefinitely .
Always check the calibra tion of a thermometer before purchase , particularly if it is an inexpensive make . The simplest way to do this is to select three or four thermometers at random , place them on a table or other support away from any draft , and allow them to come to room temperature . This should not take less than five minutes . During that time , do not touch or look at them closely , since the heat of the hand or your breath may affect their reading . At the end of five minutes , read them quickly . If the thermometers are of a reliable make , they should all agree to within one degree . Pick one that seems about average .
Figure 22 Three types of thermometers in common use among photographers .
Another kind of thermometer is the dial type . Its primary advantage is the relative ease with which it can be read , but it costs more . Because all dial thermometers are mechanically operated , they can change calibration as they get old . This is not true of the glass - rod type . If you do use a dial thermometer , check it occasionally by comparing it with an accurate glass - stem thermometer . If possible , use the same glass thermometer as a standard every time .
PRINT TRIMMERS
A good print trimmer of adequate size is a darkroom must . Print trimmers come in two types , the straight knife - blade type ( Figure 23 ) and the rotary . cutter - blade type ( Figure 24 ) The former is generally pre ferred although , in larger sizes the rotary cutter type has the advantage of convenience and low price . Many photographers make the mistake of buying too small a trimmer . Today , when . 14 x 17 or 16 x 20 enlarge ments are quite common the print trimmer should be at least eighteen and preferably twenty inches square . If there is enough volume of the standard 8 x 10 size prints to warrant it , it is best to have a small trimmer for such prints in addition to a large trimmer for the bigger prints .
Figure 23 Use a ruler or straight edge as an aid in holding a large print in place during trimming .
When purchasing a print trimmer , always check it for squareness . Select a large double - weight print that has been dried flat so that its edges are not badly buckled . Use a ruler straight - edge to hold the print down near the knife blade , as illustrated in Figure 23 , and cut off a narrow slice Press inward slightly on the knife blade to ensure a clean cut . Put the freshly cut side of the print against the ruled head of the trimmer , making sure that it lines up perfectly ( refer to Figure 23 again ) , and trim the next side . Repeat three more times so that the last cut will be from the first side of the print . If the trimmer is abso lutely square , this last strip should be equally wide at both ends . Check by folding it back on itself so as to get a direct
Figure 24 A rotary type print trimmer of recent . design .
comparison . If one end is appreciably wider than the other , the trimmer is not square and must be adjusted . Loosen the screws holding the ruler to the bed and shift the ruler very slightly at one end only . Tighten the ruler screws , and again check for squareness . This test multiplies any out - of - square condition by four , so that even the slightest inaccuracy shows up .
Keep your trimmer in perfect condition if you expect good work from it . Never use it to cut heavy cardboard mounts - two thicknesses of double - weight enlarging paper is about all it should handle for regular use . When trimming prints , always press the blade against the trimmer board lightly to ensure a sharp cut . Keep the hinge clean and properly oiled , and lubricate both cutting edges occasionally by drawing a block of paraffin wax across them . This not only gives you a cleaner working trimmer , but it prevents rusting . A well designed trimmer needs no sharpening if given proper care ; it is self - sharpening .
ENLARGING EASELS
Good enlarging easels are not cheap , but a number of excellent ones are available at reasonable prices for prints up to 11 x 14 inches . Beyond that size , costs increase sharply . If you don't do enough work to justify the purchase of a high - priced easel , you can use one of the substitute types described here .
An ordinary printing frame makes a satisfactory enlarging easel . Don't use the glass , since it only collects dust specks and requires constant cleaning . The depth of field of the enlarging lense will take care of any slight bulge in the paper . Without glass , you will need one printing frame for each paper size .
You can make an easel by taking a piece of 5 - ply wood slightly larger than the print and fasten narrow picture frame molding to three sides , as shown in Figure 25. The completed . easel should be painted at dead black .
Figure 25 Figure 26
Two types of home - built easels that can be built easily and cheaply .
A simpler easel may be made by using a piece of 5 - ply wood the same size as the enlargement and partially cutting away the corners , as illustrated in Figure 26. The paper is simply put on the board and held down at the corners with clips . This easel , too , must be painted dead black to prevent light reflection .
Commercial enlarging easels stay put because of their weight and do not shift when paper is inserted or removed . The projected image may , therefore , be accurately framed , with assurance that when a fresh sheet of enlarging paper is substituted for the focusing sheet , the easel will not have moved out of position . This is not true of light - weight home - made easels . You should devise some means of fixing the easel position so that even if it is removed entirely while the paper is inserted , it can be replaced exactly .
The simplest way of doing this is to get two steel bars , each weighing at least three to five pounds . Wrap them in ordinary wrapping paper so they don't scratch the table top , and place them against two . adjacent sides of the easel after the enlargement is properly framed and focused . ( Figure 27. ) These bars also come in handy as hold - down weights , and you will find many other uses for them in your normal photographic activities .
Figure 27 Use a pair of steel blocks covered with black paper or cloth to locate a light - weight easel and from shifting in use .
DEVELOPING TRAYS
Developing trays are available in a large variety of materials to fit individual purses and individual requirements . No single tray material is best for every purpose . This gives you some latitude of choice so you can select the materials which work best under your conditions .
In the smaller sizes , the tray material is not so important as in the larger sizes . For trays 8 x 10 and smaller , enameled steel , plastic or stainless steel are satisfactory . For long wear and heavy duty , stainless steel is best . In sizes 11 x 14 inches or larger , stainless steel becomes quite expensive and , therefore , plastic or white enameled steel trays are more popular .
CARE OF TRAYS . Trays should always be washed thoroughly after use , not just rinsed . Exhausted developer and hypo both have sludges which adhere to trays . These sludges can be wiped clean with a sponge under running water while the trays are wet , but once they have been allowed to dry they cannot be removed . without considerable difficulty . The washed trays should be rinsed in plenty of running water , drained , and wiped dry . They can then be stacked up on end . Never put trays away face up ; they will only pick up dust and require washing again before use .
After a steel - enameled tray has been used for some time , its surface becomes roughened so that it resists washing . For that reason , don't use an old hypo tray . for developing prints . The slight hypo - bath residues adhering to the enamel won't do the developer any good .
It is not advisable to nest steel - enameled trays when putting them away after use . However , if you are cramped for space and want to store trays that you do not use often , wipe them thoroughly after washing and nest them with a sheet or two of newspaper separating each tray . This will reduce the likelihood of chipping the enamel and will prevent the trays from sticking together .
معدات للغرفة المظلمة ..
أجهزة قياس الحرارة ..
قواطع الطباعة ..
توسيع الحامل ..
تطوير الصواني ..
THERMOMETERS
There are quite a number of thermometer styles in use by photographers . The more common are illustrated in Figure 22. The simplest and most accurate is the standard glass - rod type , filled either with colored liquid ( spirit ) or mercury . The spirit thermometer is easier to read and is preferred over mercury , other things being equal . Mercury is not used in the cheaper thermometers , so , as a general rule , the mercury thermometer is likely to be more reliable - unless it is known that the spirit thermom eter is a good one . Neither the mercury nor the spirit ther mometer can change calibra tion , so both will maintain their original accuracy indefinitely .
Always check the calibra tion of a thermometer before purchase , particularly if it is an inexpensive make . The simplest way to do this is to select three or four thermometers at random , place them on a table or other support away from any draft , and allow them to come to room temperature . This should not take less than five minutes . During that time , do not touch or look at them closely , since the heat of the hand or your breath may affect their reading . At the end of five minutes , read them quickly . If the thermometers are of a reliable make , they should all agree to within one degree . Pick one that seems about average .
Figure 22 Three types of thermometers in common use among photographers .
Another kind of thermometer is the dial type . Its primary advantage is the relative ease with which it can be read , but it costs more . Because all dial thermometers are mechanically operated , they can change calibration as they get old . This is not true of the glass - rod type . If you do use a dial thermometer , check it occasionally by comparing it with an accurate glass - stem thermometer . If possible , use the same glass thermometer as a standard every time .
PRINT TRIMMERS
A good print trimmer of adequate size is a darkroom must . Print trimmers come in two types , the straight knife - blade type ( Figure 23 ) and the rotary . cutter - blade type ( Figure 24 ) The former is generally pre ferred although , in larger sizes the rotary cutter type has the advantage of convenience and low price . Many photographers make the mistake of buying too small a trimmer . Today , when . 14 x 17 or 16 x 20 enlarge ments are quite common the print trimmer should be at least eighteen and preferably twenty inches square . If there is enough volume of the standard 8 x 10 size prints to warrant it , it is best to have a small trimmer for such prints in addition to a large trimmer for the bigger prints .
Figure 23 Use a ruler or straight edge as an aid in holding a large print in place during trimming .
When purchasing a print trimmer , always check it for squareness . Select a large double - weight print that has been dried flat so that its edges are not badly buckled . Use a ruler straight - edge to hold the print down near the knife blade , as illustrated in Figure 23 , and cut off a narrow slice Press inward slightly on the knife blade to ensure a clean cut . Put the freshly cut side of the print against the ruled head of the trimmer , making sure that it lines up perfectly ( refer to Figure 23 again ) , and trim the next side . Repeat three more times so that the last cut will be from the first side of the print . If the trimmer is abso lutely square , this last strip should be equally wide at both ends . Check by folding it back on itself so as to get a direct
Figure 24 A rotary type print trimmer of recent . design .
comparison . If one end is appreciably wider than the other , the trimmer is not square and must be adjusted . Loosen the screws holding the ruler to the bed and shift the ruler very slightly at one end only . Tighten the ruler screws , and again check for squareness . This test multiplies any out - of - square condition by four , so that even the slightest inaccuracy shows up .
Keep your trimmer in perfect condition if you expect good work from it . Never use it to cut heavy cardboard mounts - two thicknesses of double - weight enlarging paper is about all it should handle for regular use . When trimming prints , always press the blade against the trimmer board lightly to ensure a sharp cut . Keep the hinge clean and properly oiled , and lubricate both cutting edges occasionally by drawing a block of paraffin wax across them . This not only gives you a cleaner working trimmer , but it prevents rusting . A well designed trimmer needs no sharpening if given proper care ; it is self - sharpening .
ENLARGING EASELS
Good enlarging easels are not cheap , but a number of excellent ones are available at reasonable prices for prints up to 11 x 14 inches . Beyond that size , costs increase sharply . If you don't do enough work to justify the purchase of a high - priced easel , you can use one of the substitute types described here .
An ordinary printing frame makes a satisfactory enlarging easel . Don't use the glass , since it only collects dust specks and requires constant cleaning . The depth of field of the enlarging lense will take care of any slight bulge in the paper . Without glass , you will need one printing frame for each paper size .
You can make an easel by taking a piece of 5 - ply wood slightly larger than the print and fasten narrow picture frame molding to three sides , as shown in Figure 25. The completed . easel should be painted at dead black .
Figure 25 Figure 26
Two types of home - built easels that can be built easily and cheaply .
A simpler easel may be made by using a piece of 5 - ply wood the same size as the enlargement and partially cutting away the corners , as illustrated in Figure 26. The paper is simply put on the board and held down at the corners with clips . This easel , too , must be painted dead black to prevent light reflection .
Commercial enlarging easels stay put because of their weight and do not shift when paper is inserted or removed . The projected image may , therefore , be accurately framed , with assurance that when a fresh sheet of enlarging paper is substituted for the focusing sheet , the easel will not have moved out of position . This is not true of light - weight home - made easels . You should devise some means of fixing the easel position so that even if it is removed entirely while the paper is inserted , it can be replaced exactly .
The simplest way of doing this is to get two steel bars , each weighing at least three to five pounds . Wrap them in ordinary wrapping paper so they don't scratch the table top , and place them against two . adjacent sides of the easel after the enlargement is properly framed and focused . ( Figure 27. ) These bars also come in handy as hold - down weights , and you will find many other uses for them in your normal photographic activities .
Figure 27 Use a pair of steel blocks covered with black paper or cloth to locate a light - weight easel and from shifting in use .
DEVELOPING TRAYS
Developing trays are available in a large variety of materials to fit individual purses and individual requirements . No single tray material is best for every purpose . This gives you some latitude of choice so you can select the materials which work best under your conditions .
In the smaller sizes , the tray material is not so important as in the larger sizes . For trays 8 x 10 and smaller , enameled steel , plastic or stainless steel are satisfactory . For long wear and heavy duty , stainless steel is best . In sizes 11 x 14 inches or larger , stainless steel becomes quite expensive and , therefore , plastic or white enameled steel trays are more popular .
CARE OF TRAYS . Trays should always be washed thoroughly after use , not just rinsed . Exhausted developer and hypo both have sludges which adhere to trays . These sludges can be wiped clean with a sponge under running water while the trays are wet , but once they have been allowed to dry they cannot be removed . without considerable difficulty . The washed trays should be rinsed in plenty of running water , drained , and wiped dry . They can then be stacked up on end . Never put trays away face up ; they will only pick up dust and require washing again before use .
After a steel - enameled tray has been used for some time , its surface becomes roughened so that it resists washing . For that reason , don't use an old hypo tray . for developing prints . The slight hypo - bath residues adhering to the enamel won't do the developer any good .
It is not advisable to nest steel - enameled trays when putting them away after use . However , if you are cramped for space and want to store trays that you do not use often , wipe them thoroughly after washing and nest them with a sheet or two of newspaper separating each tray . This will reduce the likelihood of chipping the enamel and will prevent the trays from sticking together .
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