Ilford Multigrade 1762628 HAR1762628 用户手册
产品代码
HAR1762628
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Contrast control with ILFORD MULTIGRADE papers
can be achieved in several ways. These include
the ILFORD MULTIGRADE hand filters and the
ILFORD MULTIGRADE 600 equipment. Contrast
can also be controlled with other variable contrast
enlarger heads and with colour enlargers.
can be achieved in several ways. These include
the ILFORD MULTIGRADE hand filters and the
ILFORD MULTIGRADE 600 equipment. Contrast
can also be controlled with other variable contrast
enlarger heads and with colour enlargers.
CONTRAST RANGE
This section describes how MULTIGRADE papers
give different contrast levels. For practical
information on selecting contrast levels turn to the
next pages.
This section describes how MULTIGRADE papers
give different contrast levels. For practical
information on selecting contrast levels turn to the
next pages.
All chloro-bromide (black and white) emulsions are
blue sensitive with a slight sensitivity to green light.
To make an emulsion sensitive to colours in
addition to blue, sensitising dyes need to be
added.
blue sensitive with a slight sensitivity to green light.
To make an emulsion sensitive to colours in
addition to blue, sensitising dyes need to be
added.
MULTIGRADE papers are coated with an emulsion
which is a mixture of three separate emulsions.
Each emulsion is a basic blue sensitive emulsion to
which is added different amounts of green
sensitising dye. Thus, part of the mixed emulsion is
sensitive mainly to blue light, part to blue light
with some sensitivity to green light and part to
both blue and green light.
which is a mixture of three separate emulsions.
Each emulsion is a basic blue sensitive emulsion to
which is added different amounts of green
sensitising dye. Thus, part of the mixed emulsion is
sensitive mainly to blue light, part to blue light
with some sensitivity to green light and part to
both blue and green light.
All parts of the emulsion have the same contrast.
They also all have the same speed to blue light,
but naturally, the part of the emulsion with only a
small amount of green sensitising dye has a low
speed (that is, is less sensitive) to green light.
They also all have the same speed to blue light,
but naturally, the part of the emulsion with only a
small amount of green sensitising dye has a low
speed (that is, is less sensitive) to green light.
When the paper is exposed to blue light, all parts
of the emulsion react and contribute equally to the
final image. This image is of high contrast because
of the additive effect produced by three emulsions
with the same speed and contrast. The resultant
curve has a narrow exposure range and is thus of
high contrast.
of the emulsion react and contribute equally to the
final image. This image is of high contrast because
of the additive effect produced by three emulsions
with the same speed and contrast. The resultant
curve has a narrow exposure range and is thus of
high contrast.
When the paper is exposed to green light, only
the parts of the emulsion with the larger amounts
of green sensitising dye react initially. This is
because the three emulsions have very different
sensitivities to green light. This image is of low
contrast because of the additive effect produced
by three emulsions with different speeds to green
light, but with the same inherent contrast. The
the parts of the emulsion with the larger amounts
of green sensitising dye react initially. This is
because the three emulsions have very different
sensitivities to green light. This image is of low
contrast because of the additive effect produced
by three emulsions with different speeds to green
light, but with the same inherent contrast. The
resultant curve has a very much wider exposure
range and is thus of low contrast.
range and is thus of low contrast.
By varying the proportion of blue to green light, a
contrast range between these two extremes can be
obtained. The simplest way of controlling the
colour of the light reaching the emulsion during
exposure is by the use of filters: a magenta filter
absorbs green light and transmits blue; a yellow
filter absorbs blue light and transmits green. In this
way, high and low contrast images can be made.
contrast range between these two extremes can be
obtained. The simplest way of controlling the
colour of the light reaching the emulsion during
exposure is by the use of filters: a magenta filter
absorbs green light and transmits blue; a yellow
filter absorbs blue light and transmits green. In this
way, high and low contrast images can be made.
Exposure to blue light
Relative log exposure
A combined curve
B
B
dyed emulsion I
C dyed emulsion II
D dyed emulsion III
D dyed emulsion III
Exposure to green light
Relative log exposure
A combined curve
B
B
dyed emulsion I
C dyed emulsion II
D dyed emulsion III
D dyed emulsion III
CONTRAST
CONTROL
FACT SHEET
CONTRAST CONTROL
FOR ILFORD MULTIGRADE VARIABLE CONTRAST PAPERS
Density
Density
December 2001