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Rollfilm cameras
The most popular film used to be rollfilm which gave a large , 2 ins square image Today , improvements in lenses and emul- sions have made 35 mm and smaller films more popular and rollfilm has become a specialist medium size material , mostly used by professionals .
The film itself is rolled on a spool com- bined with a length of opaque backing paper . It is attached to the paper by tape at its leading edge . The backing paper is about 8 ins ( 20 cm ) longer than the film at each end so you can load in daylight by threading the leading edge on to a take - up spool in the camera . By winding a knob at the top of the take - up spool you draw the film into position . At the end of the film you continue winding , so that the backing paper end protects the film from light when you open the camera . You can then use the empty spool to act as the next take - up spool .
The most generally used rollfilm size ( 120/620 ) gives a picture 24 ins wide . Most rollfilm cameras take square pictures , 12 to a film . As you can see from the full size drawings , right , a 2 ins square picture is over four times the area of a 35 mm picture and so needs less enlargement , minimizing graininess on the print .
Two main types of rollfilm camera are widely used . The twin lens reflex , described opposite , is made in both fixed and inter- changeable lens models . The rollfilm single lens reflex , shown below , has a system of interchangeable lenses , film magazines , and other accessories .
Reflex viewing problems .
Both single and twin lens reflex rollfilm cameras use a mirror at 45 ° to reflect light from the lens up on to a horizontal focusing screen . You see the image the right way up but reversed left to right , as shown right . This makes it hard to pan ( follow ) moving subjects . You can correct this by fitting a penta- prism over the focusing screen , as in a 35 mm camera , but penta- prisms for rollfilm cameras are relatively expensive .
Single lens reflex rollfilm camera
The viewing system in the rollfilm single lens reflex camera uses the same principle as the 35 mm SLR ( see p . 29 ) . A hinged mirror reflects the image formed by the taking lens up on to a focusing screen . At the moment of exposure the mirror lifts , and a focal plane shutter fires at the back of the camera . Generally you view the focusing screen through a remov- able folding hood with a flip - up magnifier . But you can add differ- ent viewfinders or focusing screens for different purposes .
Most rollfilm SLR cameras use detachable film magazines . You pre - load these with rollfilm and clip them on to the camera back . The film is protected in the maga- zine by a thin metal dark slide , which you remove before taking any pictures . You can change from black and white to color material , instant picture film or sheet film at any time , even in mid - film- simply by switching magazines .
There is a wide range of inter- changeable lenses that fit the rollfilm SLR .
Twin lens reflex rollfilm camera
The twin lens reflex uses two lenses of identical focal length . One forms the image on the focusing screen , the same size as the picture frame . The other lens is fitted with a bladed shutter , and forms the image that records on When the image is in focus on the screen it also the film because the distances between top lens and focusing screen , and bottom lens and film are identical . Both lenses move forward and backward on the same front panel to focus . If you buy a model with interchangeable lenses you have to buy the lenses in pairs .
The internal viewing system is similar to a single reflex in design . but has a fixed mirror . However the twin lens viewing system does suffer from parallax error , as shown right .
Correcting for parallax
The 1 in ( 3.8 cm ) gap between the two lenses may lead to serious errors in close up work . For sub- jects nearer than about 8 ft ( 2.4 m ) . a pointer shows the true top of the picture . Ideally , you should use a tripod to raise the camera by the exact inter - lens distance to eliminate parallax , as shown below .
Variety of viewpoint
Despite its clumsy appearance , the twin lens reflex allows the widest range of viewpoints of any camera design . A waist - level position , or chest height if you use the folding focusing magnifier , is normal . But you can easily focus the camera at ground level . For viewpoints over people's heads or other high obstacles , you can hold the camera upside - down , above your head . The front of the hood folds down for action photography and forms a simple frame finder , viewed at eye level through an aperture at the rear . This finder is essential for panning moving subjects , but it does increase parallax error .
Other rollfilm camera formats
Square pictures are sometimes awkward to compose , and square negatives tend to waste printing paper , which is rectangular . How- ever , there are some single lens reflex cameras which take rect- angular pictures on rollfilm .
The 6x7 cm model , bottom , has a revolving back . This enables you to turn the film compartment for a horizontal or vertical format The 6x 4.5 cm camera can be fitted with a hand grip that in- cludes a shutter release and film wind lever . By folding down the front of the hood it can be oper- ated like a single lens reflex camera . Other models are fitted with penta- prisms and have similar , scaled - up controls to a normal 35 mm single lens reflex camera . A 6 × 7 cm camera gives you eight pictures , and a 6 × 4.5 cm model 16 pictures ، on a 120 rollfilm .
Rollfilm cameras
The most popular film used to be rollfilm which gave a large , 2 ins square image Today , improvements in lenses and emul- sions have made 35 mm and smaller films more popular and rollfilm has become a specialist medium size material , mostly used by professionals .
The film itself is rolled on a spool com- bined with a length of opaque backing paper . It is attached to the paper by tape at its leading edge . The backing paper is about 8 ins ( 20 cm ) longer than the film at each end so you can load in daylight by threading the leading edge on to a take - up spool in the camera . By winding a knob at the top of the take - up spool you draw the film into position . At the end of the film you continue winding , so that the backing paper end protects the film from light when you open the camera . You can then use the empty spool to act as the next take - up spool .
The most generally used rollfilm size ( 120/620 ) gives a picture 24 ins wide . Most rollfilm cameras take square pictures , 12 to a film . As you can see from the full size drawings , right , a 2 ins square picture is over four times the area of a 35 mm picture and so needs less enlargement , minimizing graininess on the print .
Two main types of rollfilm camera are widely used . The twin lens reflex , described opposite , is made in both fixed and inter- changeable lens models . The rollfilm single lens reflex , shown below , has a system of interchangeable lenses , film magazines , and other accessories .
Reflex viewing problems .
Both single and twin lens reflex rollfilm cameras use a mirror at 45 ° to reflect light from the lens up on to a horizontal focusing screen . You see the image the right way up but reversed left to right , as shown right . This makes it hard to pan ( follow ) moving subjects . You can correct this by fitting a penta- prism over the focusing screen , as in a 35 mm camera , but penta- prisms for rollfilm cameras are relatively expensive .
Single lens reflex rollfilm camera
The viewing system in the rollfilm single lens reflex camera uses the same principle as the 35 mm SLR ( see p . 29 ) . A hinged mirror reflects the image formed by the taking lens up on to a focusing screen . At the moment of exposure the mirror lifts , and a focal plane shutter fires at the back of the camera . Generally you view the focusing screen through a remov- able folding hood with a flip - up magnifier . But you can add differ- ent viewfinders or focusing screens for different purposes .
Most rollfilm SLR cameras use detachable film magazines . You pre - load these with rollfilm and clip them on to the camera back . The film is protected in the maga- zine by a thin metal dark slide , which you remove before taking any pictures . You can change from black and white to color material , instant picture film or sheet film at any time , even in mid - film- simply by switching magazines .
There is a wide range of inter- changeable lenses that fit the rollfilm SLR .
Twin lens reflex rollfilm camera
The twin lens reflex uses two lenses of identical focal length . One forms the image on the focusing screen , the same size as the picture frame . The other lens is fitted with a bladed shutter , and forms the image that records on When the image is in focus on the screen it also the film because the distances between top lens and focusing screen , and bottom lens and film are identical . Both lenses move forward and backward on the same front panel to focus . If you buy a model with interchangeable lenses you have to buy the lenses in pairs .
The internal viewing system is similar to a single reflex in design . but has a fixed mirror . However the twin lens viewing system does suffer from parallax error , as shown right .
Correcting for parallax
The 1 in ( 3.8 cm ) gap between the two lenses may lead to serious errors in close up work . For sub- jects nearer than about 8 ft ( 2.4 m ) . a pointer shows the true top of the picture . Ideally , you should use a tripod to raise the camera by the exact inter - lens distance to eliminate parallax , as shown below .
Variety of viewpoint
Despite its clumsy appearance , the twin lens reflex allows the widest range of viewpoints of any camera design . A waist - level position , or chest height if you use the folding focusing magnifier , is normal . But you can easily focus the camera at ground level . For viewpoints over people's heads or other high obstacles , you can hold the camera upside - down , above your head . The front of the hood folds down for action photography and forms a simple frame finder , viewed at eye level through an aperture at the rear . This finder is essential for panning moving subjects , but it does increase parallax error .
Other rollfilm camera formats
Square pictures are sometimes awkward to compose , and square negatives tend to waste printing paper , which is rectangular . How- ever , there are some single lens reflex cameras which take rect- angular pictures on rollfilm .
The 6x7 cm model , bottom , has a revolving back . This enables you to turn the film compartment for a horizontal or vertical format The 6x 4.5 cm camera can be fitted with a hand grip that in- cludes a shutter release and film wind lever . By folding down the front of the hood it can be oper- ated like a single lens reflex camera . Other models are fitted with penta- prisms and have similar , scaled - up controls to a normal 35 mm single lens reflex camera . A 6 × 7 cm camera gives you eight pictures , and a 6 × 4.5 cm model 16 pictures ، on a 120 rollfilm .
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