تويت
التصوير الفوتوغرافي الحديث
فن النسخ
كاميرا النسخ، عدسة النسخ، التعامل مع الأصول،
ما الفيلم لاستخدامه
THE COPY CAMERA
For the photographer who does a great deal of copying and wants a substantial and permanent set - up , best results will be obtained with copy cameras which are especially designed for such work . Such cameras are built along the lines of studio or view cameras except that they are especially rigid and have long bellows extensions .
If you do not intend doing enough copying to make the purchase of a commercial copying camera advisable , the second choice is a solid home portrait or view camera with double extension . The longer the extension the better , since a longer extension will enable you to get closer to the copy and produce larger images . The very least extension you should consider for your copy camera is twice the focal length of the lens . This will enable you to make full - size copies . Additional extension will enable you to enlarge the picture slightly , which is often an advantage , since many pictures can be improved by a little cropping .
THE COPY LENS
The very best lens for copying purposes is a process lens . A lens of this type is specifically designed to produce sharpest images when the original and the negative at approximately equal distances from the lens . A camera lens , on the other hand , will give sharpest results when the image is less than 1/3 the subject size . Process lenses are also apochromats , which means they are corrected for three colors instead of only two as is the case for ordinary camera lenses . Process lenses will , therefore , give sharper reproductions of colored pictures . If you are copying with a 35mm camera , the best lens to use is a macro lens because it is specifically corrected to have a flat field at close distances .
Process lenses , unfortunately , are very expensive . Since extreme sharpness is usually not required , any good commercial lens will do , particularly if it is stopped down to about f / 11 or even f / 16 . If you focus carefully , it is not advisable to stop down below this because the copy is in one plane and you do not need great depth of field . With many short - focus lenses , stopping down below f / 11 actually decreases sharpness .
You must focus the image very carefully , getting it absolutely sharp and clear . It is a good plan to use a focusing magnifier to make sure you have the image as sharp as possible . Sometimes it is a help in focusing to place a piece of printed matter in contact with the copy and focus on that . This gives you sharp lines to focus on .
HANDLING THE ORIGINALS
If your copy stand is of the vertical type , holding the material to be copied in the correct position is no problem - you simply lay it down on the easel . However , if you have a horizontal copy stand , you must provide means of holding the copied material against the easel .
Usually the photograph or drawing you want to copy can be attached to the easel board with thumb tacks . Do not put pins through the original , but push the tacks into the easel close to it so that the edges will be gripped by the head of the tack . In this way you will not damage the material to be copied . If you have to copy the entire picture and the thumb tacks would show , use double surfaced pressure - sensitive tape to hold it in place . This tape is like ordinary tape , except that there is adhesive on both sides . Simply press some small strips of this tape against the back of the print to be copied and then press the print against the easel . This will hold it in place long enough for it to be copied .
WHAT FILM TO USE
The choice of film available for copy work is wide indeed - and the correct choice for any particular job depends first of all on the nature of the original material to be copied and secondly , on the use to which the copy is to be put . For the purposes of this discussion , we will consider the copy material as being capable of classification under one of two headings : continuous tone copy and line copy . Under continuous tone , we would list photographs , paintings and anything else which can have a continuous variation in brightness from black to white . Line copy covers material which is composed of solid black and solid white areas , with no in - between shades of gray . The printed page , a pen and ink diagram , and a hand - written letter are good examples of line copy .
For continuous tone copying , almost any film may be used . If the original has normal contrast , you can use any normal , medium such as you would use for general purpose photography . However , if the original is excessively soft and flat so that you will wish to build up its contrast in making the copy , you can resort to one of the finer grained slow films , since such films generally have somewhat more contrast . If sheet film is used , your choice would be one of the slow commercial films . Bear in mind that whatever film you use , except for some of the very fast films , you can achieve a considerable variation in contrast by varying development time to give you the exact degree of contrast you want .
When photographing line copy , you are concerned with getting a deep rich black and a pure white - there must be no grays whatsoever . This , of course , means that you want contrast . Where the original has reasonably good contrast in itself , you can usually get very satisfactory results through the use of the slow , fine - grain films if you use a roll film camera , or the slow commercial films if you use sheet films in your camera . Exposure should be correct , since overexposure tends to cause the whites to broaden , thus losing some of the fine black lines in the copy , while underexposure makes it difficult to get a good black . Development of the negative should be on the full side , however , to achieve maximum usable contrast . If necessary , development can be increased by 25 , 50 or even 100 % depending upon the film and developer used , and the degree of contrast increase needed .
If you need more contrast than you can get with the films mentioned above you can resort to the special high contrast emulsions designed primarily for line copy work such as Kodalith emulsions which are available only in 35mm rolls and in sheet film .
فن النسخ
كاميرا النسخ، عدسة النسخ، التعامل مع الأصول،
ما الفيلم لاستخدامه
THE COPY CAMERA
For the photographer who does a great deal of copying and wants a substantial and permanent set - up , best results will be obtained with copy cameras which are especially designed for such work . Such cameras are built along the lines of studio or view cameras except that they are especially rigid and have long bellows extensions .
If you do not intend doing enough copying to make the purchase of a commercial copying camera advisable , the second choice is a solid home portrait or view camera with double extension . The longer the extension the better , since a longer extension will enable you to get closer to the copy and produce larger images . The very least extension you should consider for your copy camera is twice the focal length of the lens . This will enable you to make full - size copies . Additional extension will enable you to enlarge the picture slightly , which is often an advantage , since many pictures can be improved by a little cropping .
THE COPY LENS
The very best lens for copying purposes is a process lens . A lens of this type is specifically designed to produce sharpest images when the original and the negative at approximately equal distances from the lens . A camera lens , on the other hand , will give sharpest results when the image is less than 1/3 the subject size . Process lenses are also apochromats , which means they are corrected for three colors instead of only two as is the case for ordinary camera lenses . Process lenses will , therefore , give sharper reproductions of colored pictures . If you are copying with a 35mm camera , the best lens to use is a macro lens because it is specifically corrected to have a flat field at close distances .
Process lenses , unfortunately , are very expensive . Since extreme sharpness is usually not required , any good commercial lens will do , particularly if it is stopped down to about f / 11 or even f / 16 . If you focus carefully , it is not advisable to stop down below this because the copy is in one plane and you do not need great depth of field . With many short - focus lenses , stopping down below f / 11 actually decreases sharpness .
You must focus the image very carefully , getting it absolutely sharp and clear . It is a good plan to use a focusing magnifier to make sure you have the image as sharp as possible . Sometimes it is a help in focusing to place a piece of printed matter in contact with the copy and focus on that . This gives you sharp lines to focus on .
HANDLING THE ORIGINALS
If your copy stand is of the vertical type , holding the material to be copied in the correct position is no problem - you simply lay it down on the easel . However , if you have a horizontal copy stand , you must provide means of holding the copied material against the easel .
Usually the photograph or drawing you want to copy can be attached to the easel board with thumb tacks . Do not put pins through the original , but push the tacks into the easel close to it so that the edges will be gripped by the head of the tack . In this way you will not damage the material to be copied . If you have to copy the entire picture and the thumb tacks would show , use double surfaced pressure - sensitive tape to hold it in place . This tape is like ordinary tape , except that there is adhesive on both sides . Simply press some small strips of this tape against the back of the print to be copied and then press the print against the easel . This will hold it in place long enough for it to be copied .
WHAT FILM TO USE
The choice of film available for copy work is wide indeed - and the correct choice for any particular job depends first of all on the nature of the original material to be copied and secondly , on the use to which the copy is to be put . For the purposes of this discussion , we will consider the copy material as being capable of classification under one of two headings : continuous tone copy and line copy . Under continuous tone , we would list photographs , paintings and anything else which can have a continuous variation in brightness from black to white . Line copy covers material which is composed of solid black and solid white areas , with no in - between shades of gray . The printed page , a pen and ink diagram , and a hand - written letter are good examples of line copy .
For continuous tone copying , almost any film may be used . If the original has normal contrast , you can use any normal , medium such as you would use for general purpose photography . However , if the original is excessively soft and flat so that you will wish to build up its contrast in making the copy , you can resort to one of the finer grained slow films , since such films generally have somewhat more contrast . If sheet film is used , your choice would be one of the slow commercial films . Bear in mind that whatever film you use , except for some of the very fast films , you can achieve a considerable variation in contrast by varying development time to give you the exact degree of contrast you want .
When photographing line copy , you are concerned with getting a deep rich black and a pure white - there must be no grays whatsoever . This , of course , means that you want contrast . Where the original has reasonably good contrast in itself , you can usually get very satisfactory results through the use of the slow , fine - grain films if you use a roll film camera , or the slow commercial films if you use sheet films in your camera . Exposure should be correct , since overexposure tends to cause the whites to broaden , thus losing some of the fine black lines in the copy , while underexposure makes it difficult to get a good black . Development of the negative should be on the full side , however , to achieve maximum usable contrast . If necessary , development can be increased by 25 , 50 or even 100 % depending upon the film and developer used , and the degree of contrast increase needed .
If you need more contrast than you can get with the films mentioned above you can resort to the special high contrast emulsions designed primarily for line copy work such as Kodalith emulsions which are available only in 35mm rolls and in sheet film .
تعليق