Advanced Photography Course

product conforms closely to the desired tonal values
(based on a D-min of 0.40).

Trigradient Control Curves

As stated previously, the trigradient tone

reproduction method is based on three tone-control
curves (or printer curves): high contrast, medium
contrast, and low contrast.

Basically, the printer curves are produced the same

way that sensi-strips are made for process monitoring.
Instead of using a sensitometer to expose the film, the
contact printer is used to expose the film through a step
tablet. Since the amount of exposure is unknown, the
horizontal axis of the curve indicates the density of the
step tablet. The vertical axis represents the density
produced after the duplicating film is exposed through
the step tablet and processed.

Each set of printer curves consists of a family of

response curves that graphically display the various
tones produced in the duplicating material when it is
printed under various exposure and processing
conditions. Each curve is labeled with the exposure
setting used on the printer to create the curve (figs. 4-30,
4-31, and 4-32). These response curves enable the

density range of the imagery to be altered, so the density
range of the final product conforms closely to the
desired density range (1.00). The exposure of the
printer is important since it determines the placement of
the tonal values of the imagery being reproduced on the
sensitometric response curve of the duplicating

material. Ideally, all tones should fall on the
straight-line portion of the response curve to ensure that

the images are reproduced uniformly. The D-max of
the imagery being duplicated is used to determine the
required exposure since it reproduces as the D-min in
the reproduction.

Trigradient Tone Reproduction Procedures

The following procedures are used in the trigradient

tone reproduction system:

1. Obtain the three sets of tone control curves

(high, medium, and low contrasts) for the particular
duplicating materials being used.

2. Determine the D-max and D-min densities on

the roll of imagery to be duplicated. Remember, the
D-max and D-min are the areas in which you want to
retain detail, not necessarily the areas of highest and
lowest density. Do not use specular highlights or

completely black areas to represent the D-max and
D-min.

3. Determine the density range in the original, and

determine whether the tonal range should be increased,
retained, or decreased. Do this to obtain the desired
density range (usually 1.0) on the duplicate.

4. Based upon results of step 3, select the set of

response curves closest to the density range (high,
medium, or low).

5. On the horizontal axis, locate the density of the

step tablet that corresponds to the D-min density that
you selected. Go up from this point until you intersect

the 1.40 line and draw a tick mark.

6. On the horizontal axis, locate the density of the

step tablet that corresponds to the D-max density that
you selected. Go up from this point until you intersect

the 0.40 line and draw a tick mark.

7. Using a straightedge, select the characteristic

curve closest to your straight line. If the curves cross,
choose the curve closest to your D-max because this
density controls the exposure of the D-min on the
duplicate.

8. Expose and process the duplicate film according

to your determination in step 7.

9. Read the D-max and D-min of the duplicate

film. If these values are not within established
tolerances (0.05, for example), another duplicate must
be made. Minor adjustments in exposure or processing
may have to be made. For example, if the D-min is too

high, then less exposure is required. If the D-min is
within tolerance but the D-max is too low, then more
development is required (to raise the contrast).

The entire tone control system is based upon data

produced when the system is established. For the
system to be accurate and reliable, all of the major
variables must be controlled so they can be carried out
on a repetitive basis.

CAPTIONING AERIAL

PHOTOGRAPHY

Captioning and slating hand-held aerial

photography is as important as captioning and slating
still and motion-picture photography that is taken on the
ground. In captioning aerial photography, however, the
caption information should be expanded to include the
camera lens focal length, the altitude, and the direction
of the aircraft from which the picture was made and the
time of day the photograph was taken.

4-40

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Advanced Photography Course

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DOFMaster for Windows On-line Depth of Field Calculator DOFMaster for Mobile Devices On-line Depth of Field Table Hyperfocal Distance Chart Articles FAQ Recommended Books Support Contact Links Home As an Amazon Associate I earn from qualifying purchases.	contents <- previous page next page -> product conforms closely to the desired tonal values (based on a D-min of 0.40). Trigradient Control Curves As stated previously, the trigradient tone reproduction method is based on three tone-control curves (or printer curves): high contrast, medium contrast, and low contrast. Basically, the printer curves are produced the same way that sensi-strips are made for process monitoring. Instead of using a sensitometer to expose the film, the contact printer is used to expose the film through a step tablet. Since the amount of exposure is unknown, the horizontal axis of the curve indicates the density of the step tablet. The vertical axis represents the density produced after the duplicating film is exposed through the step tablet and processed. Each set of printer curves consists of a family of response curves that graphically display the various tones produced in the duplicating material when it is printed under various exposure and processing conditions. Each curve is labeled with the exposure setting used on the printer to create the curve (figs. 4-30, 4-31, and 4-32). These response curves enable the density range of the imagery to be altered, so the density range of the final product conforms closely to the desired density range (1.00). The exposure of the printer is important since it determines the placement of the tonal values of the imagery being reproduced on the sensitometric response curve of the duplicating material. Ideally, all tones should fall on the straight-line portion of the response curve to ensure that the images are reproduced uniformly. The D-max of the imagery being duplicated is used to determine the required exposure since it reproduces as the D-min in the reproduction. Trigradient Tone Reproduction Procedures The following procedures are used in the trigradient tone reproduction system: 1. Obtain the three sets of tone control curves (high, medium, and low contrasts) for the particular duplicating materials being used. 2. Determine the D-max and D-min densities on the roll of imagery to be duplicated. Remember, the D-max and D-min are the areas in which you want to retain detail, not necessarily the areas of highest and lowest density. Do not use specular highlights or completely black areas to represent the D-max and D-min. 3. Determine the density range in the original, and determine whether the tonal range should be increased, retained, or decreased. Do this to obtain the desired density range (usually 1.0) on the duplicate. 4. Based upon results of step 3, select the set of response curves closest to the density range (high, medium, or low). 5. On the horizontal axis, locate the density of the step tablet that corresponds to the D-min density that you selected. Go up from this point until you intersect the 1.40 line and draw a tick mark. 6. On the horizontal axis, locate the density of the step tablet that corresponds to the D-max density that you selected. Go up from this point until you intersect the 0.40 line and draw a tick mark. 7. Using a straightedge, select the characteristic curve closest to your straight line. If the curves cross, choose the curve closest to your D-max because this density controls the exposure of the D-min on the duplicate. 8. Expose and process the duplicate film according to your determination in step 7. 9. Read the D-max and D-min of the duplicate film. If these values are not within established tolerances (0.05, for example), another duplicate must be made. Minor adjustments in exposure or processing may have to be made. For example, if the D-min is too high, then less exposure is required. If the D-min is within tolerance but the D-max is too low, then more development is required (to raise the contrast). The entire tone control system is based upon data produced when the system is established. For the system to be accurate and reliable, all of the major variables must be controlled so they can be carried out on a repetitive basis. CAPTIONING AERIAL PHOTOGRAPHY Captioning and slating hand-held aerial photography is as important as captioning and slating still and motion-picture photography that is taken on the ground. In captioning aerial photography, however, the caption information should be expanded to include the camera lens focal length, the altitude, and the direction of the aircraft from which the picture was made and the time of day the photograph was taken. 4-40 contents Advanced Photography Course <- previous page next page ->	As an Amazon Associate I earn from qualifying purchases.
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