Durst M 670 COLOR Operating Manual - Page 11

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Rule 5:

The higher the filter setting, the more the exposure time

increases. This applies especially to magenta and cyan.

Rule 6:

Preferably mark the filter setting, exposure time and lens

aperture on the back of every test and every print.

Rule 7:

Judge the colour effect by daylight or by a daylight-matching

light sourCe.

Note to Rule 5:

To ensure correct exposure of subsequent prints after

increasing the filter settings, you have to recalculate the

exposure time for every change in filter value. Use the

exposure factors listed in the table below, entering them in the

following equation:

(F1 x F2 x F3) new

T (new)

T (old) x· (F1 x F2x 1=3) old

T (new)

new exposure time

T (old)

old exposure time

(F1 x F2 x F3) new

new exposure factors

(F1 x F2 x F3) old

old exposure factors

Filter exposure factors

Filter value

Yellow

Magenta

Cyan

100

105

110

115

120

125

130

1.00

1.02

1.04

1.06

1.08

1.10

1.11

1.12

1.13

1.14

1.15

1.16

1.17

1.18

1.19

1.20

1.21

1.00

1.08

1.15

1.21

1.26

1.31

1.36

1.40

1.44

1.48

1.52

1.56

1.60

1.64

1.68

1.71

1.74

1.77

1.80

1.83

1.86

1.89

1.92

1.95

1.98

2.01

2.04

1.00

1.06

1.11

1.16

1.20

1.24

1.28

1.31

1.34

1.37

1.40

1.43

1.46

1.49

1.52

1.54

1.56

1.58

1.60

1.62

1.64

1.66

1.68

1.70

1.72

1.74

1.76

Practical examples

Example 1:

New filter settings

Old filter settings

If the old exposure time was 10 seconds, what is the new time?

I n the table look up the filter factors of the new and old filter

settings and enter them in the equation:

(F1 x F2 x F3) new

T (new)

T (old) x (F1 x F2 x F3) old

1.08 x 1.44 x 1

10 x

1.08X1.15X1

12.5 sec.

Example 2:

New filter settings

Old filter settings

If the old exposure time was 20 seconds, what is the new time?

In the table look up the filter factors of the new and old filter

settings and enter them in the equation:

20 x 1.08x1.00X1.00

T (new)

17.4 sec.

1.08X1.15x1.00

Note that the magnification must not change while you are

making the filter test. After every change in the filter setting

make a new test print until you have the best filter combination.

Then make the final enlargement. Using a colour analyser

or meter greatly simplifies and speeds up this procedure.

Comparison of Durst, Kodak, Agfa and Clba filter values

Kodak/Ciba

Durst

50 yellow

30 yellow in colour mixing head

50 magenta

30 magenta in colour mixing head

50 cyan

30 cyan in colour mixing head

Agfa

Durst

50 yellow

25 yellow in colour mixing head

50 magenta

25 magenta in colour mixing head

50 cyan

25 cyan in colour mixing head.

Black-and-white enlargements on variable-contrast papers

with the Durst M 670 COlOR

With variable-contrast papers you can enlarge all your prints

on a paper of single gradation. The contrast response is

controlled by suitably filtered exposing light. With a yellow

filter the gradation becomes flatter, i.e. the print softer; with

a magenta filter the gradation becomes steeper and the print

more contrasty.

The table below shows the required filter settings to obtain

different equivalent paper grades:

Filter settings on

colour head for

Paper

IIfospeed

Kodak

grade

Multigrade

Polycontrast

0.5

1.5

2.5

130

3.5

not possible

4.5

130

not possible

Note: The values are a guide only.

With the above filter settings the exposure time is automat

ically compensated

exposures can remain constant.

Accessories for black-and-whlte enlargements with the

Durst M 670 COlOR

If you have a Durst M 670 COLOR enlarger and specially want

to convert it to black-and-white operation, you can use a

VEGAKIT SW conversion kit (available separately) of the

following items:

Condenser lamphouse

- Lamp holder

- Condenser for all film sizes from 13 X 17 mm up to

24X36 mm

- 150 watt opal lamp.