تويت
التصوير الفوتوغرافي الحديث
تحديد الوضع الصحيح ..
خصائص التصوير الفوتوغرافي
الخصائص الفيزيائية ..
تخزين مواد التصوير الفوتوغرافي ..
الخلاصة ..
PHYSICAL PROPERTIES
ROLL FILM . The Eastman Kodak Company revolutionized photography for the amateur when it introduced the Kodak with daylight loading roll film in 1890 Since then , roll film has become familiar to almost everyone , and it is
unquestionably the simplest and easiest to handle of all negative material . A roll - film cartridge consists of a metal or wood spool around which is wound a long strip of protective opaque paper . Fastened to the inside of the opaque paper is the strip of film , which is considerably shorter and somewhat narrower than the paper so that it is protected from the light . The film itself consists of a thin sheet of plastic , the front side of which is coated with a sensitized gelatin emulsion . The other side is coated with a layer of plain ( or colored ) gelatin to prevent curling and halation , as explained above .
When the spool is put into the camera for use , the end of the paper is inserted into the slot of another spool and wound up enough to keep it in place . The camera is then closed and the second , or take - up spool is wound up until the film is in position in back of the lens . After each exposure , another section of the film is wound onto the take - up spool until all the film is used up . When all the film is exposed , the take - up spool is turned until all the paper backing is wound up on the spool , after which the camera is opened , the end of the protective paper gummed down to prevent it from unrolling , and the roll removed .
To provide double the film length of the standard 2 % in . wide spools ( size 120 ) , film manufacturers have recently introduced a new type of roll film which is identified as the 220. The film length is twice that of the 120 size , so that a roll of 220 provides 24 exposures in a 24 x 24 camera . To keep the diameter of the 220 spool of film the same as the 120 , the paper backing for the film has been eliminated , and paper is used only at the beginning and end of the film for protection in loading and unloading .
35mm FILM . Thirty - five millimeter film was originally designed for motion picture use , for which was spooled in large rolls of 1000 and 2000 feet . Because it was necessary to conserve space and because of the system used to process motion picture film , it was not practical to coat the back of the film with a layer of gelatin to prevent curling . Instead of gelatin , therefore , a very thin backing was applied to the film base during the process of manufacture . This backing serves the same purpose .
The 35mm film package for still camera use is manufactured in the same manner as the film for motion picture use . For that reason , it doesn't have a gelatin backing nor protective paper . Instead of the paper , a light - tight cartridge is used as the film container .
FILM PACK . A film pack is a light - tight case made of thin steel , containing 16 . individual sheets of film about the same thickness as roll film . Numbered paper tabs project from the pack , and as each film sheet is exposed , the numbered tab is pulled out as far as it will go . Pulling this tab draws the film down from the front up into a light - tight compartment in the back , leaving another film ready to be exposed . The tab is then torn off and thrown away . When the last tab is pulled , the pack may be removed in daylight and another slipped into the camera .
Film packs have the important advantage that each sheet is separate from the others . It is , therefore , possible to open the pack in the darkroom at any time and remove the exposed film without affecting the others . For that reason , it isn't necessary to expose the entire pack before any can be developed , as in the case of roll film . It is well , however , not to make this technique a regular practice , since the removal of more than five or six sheets lessens tension on the internal spring that presses the film to the front of the pack .
Fig . 27 General design of the normal film pack . Of course , the pack is much narrower than shown here . The largest packs are for 4 x 5 film .
Against this advantage , film packs have two very important disadvantages . They cost more , size for size , than either roll film or sheet film . A much more serious matter , however , is the fact that the film is quite thin . As a result , it tends to buckle and go slightly out of focus . It is not recommended in the larger sizes which , of course , are liable to buckle much more than the smaller sizes , nor is it very satisfactory with very fast lenses . When a fast lens is used wide open , it has a very shallow depth of focus , so that the slightest buckle in the film will throw portions of the image out of focus .
SHEET FILM . Sheet film ( formerly referred to as cut film ) has for some time been the standard negative material for the professional photographer . They are individual sheets of fairly - stiff plastic , coated on one side with the sensitive gelatin emulsion , and on the other with plain or dyed gelatin to prevent curling and halation . They are individually packed in paper boxes with soft black paper in between sheets to protect the sensitive surfaces . For use they are loaded into wooden film holders , each holder containing two sheets of film . It is still common practice to call these holders " plate holders , " although actually they are made for sheet film and will not accommodate glass plates .
Sheet film is stiff enough to stay in position without appreciable buckling and is , therefore , entirely satisfactory in the large , commercial sizes . Because of its lighter weight and less fragile nature , sheet film has completely replaced glass plates , except for some very special applications .
Sheet Film Notching Code . All sheet film has a series of notches cut into one of the short sides . ( Figure 13 , Assignment 4 ) This notching serves two purposes : it tells you which is the emulsion side in the dark , and it identifies the type of film . When the film is turned so that the notches are on the right side near the top edge , the emulsion side is facing you .
Every film manufacturer has his own notching code and no two types of notches are alike . You can , therefore , tell the make and type of film by the number and style of its notches . Every package of sheet film contains an instruction sheet giving this code , or you can get it from the manufacturer .
STORAGE OF PHOTOGRAPHIC MATERIALS
All sensitive photographic film should be stored in a cool , dry location where it can be protected from heat , dampness , or gases such as coal gas or motor exhaust gas . Dampness and gas fumes are particularly injurious to emulsions . The moisture greatly reduces the life of the sensitive coating and the gas fumes fog it .
CONCLUSION
In this Assignment you have learned some very interesting and useful things about the importance of successful exposure , and the right film for good black - and - white pictures . You learned of the importance of exposure latitude , and why film needs just the right amount of exposure . You learned something about the results of underexposure and overexposure ; how various films react to incorrect exposure .
You learned that there are four important factors in determining correct exposure : the type of subject , the intensity of the light , the speed of the lens , and the speed of the film .
An important section of this Assignment also dealt with the use of exposure meters for measuring incident light and reflected light . The specific instructions given on the use of these meters , and the allowable range of exposure which can be calculated with exposure meters , will be extremely helpful to you . Special light - reading techniques were discussed for unusual photographic situations .
In the last part of the Assignment , black - and - white films were discussed . We classified them with regard to their photographic and physical properties . We learned that modern panchromatic films are sensitive to the complete range of colors , while orthochromatic films are sensitive to all colors but red . The effect of silver bromide grain size was discussed along with application of different speed films for different purposes . In this connection , we learned that film speed and grain size are very closely related .
تحديد الوضع الصحيح ..
خصائص التصوير الفوتوغرافي
الخصائص الفيزيائية ..
تخزين مواد التصوير الفوتوغرافي ..
الخلاصة ..
PHYSICAL PROPERTIES
ROLL FILM . The Eastman Kodak Company revolutionized photography for the amateur when it introduced the Kodak with daylight loading roll film in 1890 Since then , roll film has become familiar to almost everyone , and it is
unquestionably the simplest and easiest to handle of all negative material . A roll - film cartridge consists of a metal or wood spool around which is wound a long strip of protective opaque paper . Fastened to the inside of the opaque paper is the strip of film , which is considerably shorter and somewhat narrower than the paper so that it is protected from the light . The film itself consists of a thin sheet of plastic , the front side of which is coated with a sensitized gelatin emulsion . The other side is coated with a layer of plain ( or colored ) gelatin to prevent curling and halation , as explained above .
When the spool is put into the camera for use , the end of the paper is inserted into the slot of another spool and wound up enough to keep it in place . The camera is then closed and the second , or take - up spool is wound up until the film is in position in back of the lens . After each exposure , another section of the film is wound onto the take - up spool until all the film is used up . When all the film is exposed , the take - up spool is turned until all the paper backing is wound up on the spool , after which the camera is opened , the end of the protective paper gummed down to prevent it from unrolling , and the roll removed .
To provide double the film length of the standard 2 % in . wide spools ( size 120 ) , film manufacturers have recently introduced a new type of roll film which is identified as the 220. The film length is twice that of the 120 size , so that a roll of 220 provides 24 exposures in a 24 x 24 camera . To keep the diameter of the 220 spool of film the same as the 120 , the paper backing for the film has been eliminated , and paper is used only at the beginning and end of the film for protection in loading and unloading .
35mm FILM . Thirty - five millimeter film was originally designed for motion picture use , for which was spooled in large rolls of 1000 and 2000 feet . Because it was necessary to conserve space and because of the system used to process motion picture film , it was not practical to coat the back of the film with a layer of gelatin to prevent curling . Instead of gelatin , therefore , a very thin backing was applied to the film base during the process of manufacture . This backing serves the same purpose .
The 35mm film package for still camera use is manufactured in the same manner as the film for motion picture use . For that reason , it doesn't have a gelatin backing nor protective paper . Instead of the paper , a light - tight cartridge is used as the film container .
FILM PACK . A film pack is a light - tight case made of thin steel , containing 16 . individual sheets of film about the same thickness as roll film . Numbered paper tabs project from the pack , and as each film sheet is exposed , the numbered tab is pulled out as far as it will go . Pulling this tab draws the film down from the front up into a light - tight compartment in the back , leaving another film ready to be exposed . The tab is then torn off and thrown away . When the last tab is pulled , the pack may be removed in daylight and another slipped into the camera .
Film packs have the important advantage that each sheet is separate from the others . It is , therefore , possible to open the pack in the darkroom at any time and remove the exposed film without affecting the others . For that reason , it isn't necessary to expose the entire pack before any can be developed , as in the case of roll film . It is well , however , not to make this technique a regular practice , since the removal of more than five or six sheets lessens tension on the internal spring that presses the film to the front of the pack .
Fig . 27 General design of the normal film pack . Of course , the pack is much narrower than shown here . The largest packs are for 4 x 5 film .
Against this advantage , film packs have two very important disadvantages . They cost more , size for size , than either roll film or sheet film . A much more serious matter , however , is the fact that the film is quite thin . As a result , it tends to buckle and go slightly out of focus . It is not recommended in the larger sizes which , of course , are liable to buckle much more than the smaller sizes , nor is it very satisfactory with very fast lenses . When a fast lens is used wide open , it has a very shallow depth of focus , so that the slightest buckle in the film will throw portions of the image out of focus .
SHEET FILM . Sheet film ( formerly referred to as cut film ) has for some time been the standard negative material for the professional photographer . They are individual sheets of fairly - stiff plastic , coated on one side with the sensitive gelatin emulsion , and on the other with plain or dyed gelatin to prevent curling and halation . They are individually packed in paper boxes with soft black paper in between sheets to protect the sensitive surfaces . For use they are loaded into wooden film holders , each holder containing two sheets of film . It is still common practice to call these holders " plate holders , " although actually they are made for sheet film and will not accommodate glass plates .
Sheet film is stiff enough to stay in position without appreciable buckling and is , therefore , entirely satisfactory in the large , commercial sizes . Because of its lighter weight and less fragile nature , sheet film has completely replaced glass plates , except for some very special applications .
Sheet Film Notching Code . All sheet film has a series of notches cut into one of the short sides . ( Figure 13 , Assignment 4 ) This notching serves two purposes : it tells you which is the emulsion side in the dark , and it identifies the type of film . When the film is turned so that the notches are on the right side near the top edge , the emulsion side is facing you .
Every film manufacturer has his own notching code and no two types of notches are alike . You can , therefore , tell the make and type of film by the number and style of its notches . Every package of sheet film contains an instruction sheet giving this code , or you can get it from the manufacturer .
STORAGE OF PHOTOGRAPHIC MATERIALS
All sensitive photographic film should be stored in a cool , dry location where it can be protected from heat , dampness , or gases such as coal gas or motor exhaust gas . Dampness and gas fumes are particularly injurious to emulsions . The moisture greatly reduces the life of the sensitive coating and the gas fumes fog it .
CONCLUSION
In this Assignment you have learned some very interesting and useful things about the importance of successful exposure , and the right film for good black - and - white pictures . You learned of the importance of exposure latitude , and why film needs just the right amount of exposure . You learned something about the results of underexposure and overexposure ; how various films react to incorrect exposure .
You learned that there are four important factors in determining correct exposure : the type of subject , the intensity of the light , the speed of the lens , and the speed of the film .
An important section of this Assignment also dealt with the use of exposure meters for measuring incident light and reflected light . The specific instructions given on the use of these meters , and the allowable range of exposure which can be calculated with exposure meters , will be extremely helpful to you . Special light - reading techniques were discussed for unusual photographic situations .
In the last part of the Assignment , black - and - white films were discussed . We classified them with regard to their photographic and physical properties . We learned that modern panchromatic films are sensitive to the complete range of colors , while orthochromatic films are sensitive to all colors but red . The effect of silver bromide grain size was discussed along with application of different speed films for different purposes . In this connection , we learned that film speed and grain size are very closely related .
تعليق