Advanced Photography Course

9. When the source of the out-of-control

condition is found and corrected, repeat procedures in

steps 1 through 6.

LIMITS AND TOLERANCES

Once the mean or standard has been established,

action and control limits are set according to the
appropriate monitoring manual. The action limits act
as "early warning" limits. Production work can still
be processed when the action limit is exceeded, but
this indicates that a condition exists that needs to be
corrected or the process may drift out of control.
Once the process drifts out of control, you should stop
production until the problem is corrected. If a control
strip shows that the control limits have been exceeded,
confirm this with a second strip; then refer to the
appropriate monitoring manual and stop production
until the trouble is corrected.

As you continue to plot control values, you will

see a random variation around the process mean over
which you have little control. As long as the control

limits are not exceeded, acceptable quality can be

expected.

COLOR PROCESS CONTROL CHARTS

A good control program uses control charts and

subjective print quality analysis in decision making.
A control chart provides a tool to avoid situations
where a serious processing error is compensated for in
printing to keep print quality acceptable. An imaging
facility that is compensating for errors near or beyond
the control limits is certain to have more quality
problems than a facility operating within acceptable
standards.

Preparing a control chart, such as the Kodak Color

Process Record Form, No. Y-55, is quite easy.
Follow this 8-step procedure:

1. Use a separate chart for each processing

machine.

2. Record the reference strip code number and

the reference values in the appropriate places. Use
color pencils to distinguish the red, green, and blue
densities when recording the reference values.

3. Draw horizontal lines to represent the mean,

action limits, and upper- and lower-control limits.

4. Record the process and machine number.

5. When plotting the control values, record the

date and time that the control strip was processed (not
read), and note any chemical or mechanical changes
made as a result of the plots.

6. Plot control values having a plus sign above

the line that represents the reference value, and plot
control values with a minus sign below the reference
value line.

7. Connect the points to provide a continuous

graph.

8. When changing to a new control strip code

number, note it on the chart. Record the date and the
new reference values and limits.

The control charts shown in figure 2-18 are not

intended to represent an actual control film or process.
It is used for illustration purposes only to show
patterns that can occur on actual control charts.

Processing Control Strips

Once control charts are established, control strips

must be processed on a regular basis. Each color
product has a particular control strip with a particular
format. In a sink-line process, a control strip should
be processed with each run of production film because
of human variables. In continuous (machine)

processors, control strips should be processed as
follows:

Before processing production work at the

beginning of the workday, or shift, or after
a long shutdown, such as a weekend.

Along with production work, at various times
throughout the day.

At the end of each workday, or shift.

After any chemical or mechanical change. Be
sure to indicate this change on the control

chart.

Whenever fresh chemicals are used in the

process. Make a note of this on the control
chart.

2-34

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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 -> 9. When the source of the out-of-control condition is found and corrected, repeat procedures in steps 1 through 6. LIMITS AND TOLERANCES Once the mean or standard has been established, action and control limits are set according to the appropriate monitoring manual. The action limits act as "early warning" limits. Production work can still be processed when the action limit is exceeded, but this indicates that a condition exists that needs to be corrected or the process may drift out of control. Once the process drifts out of control, you should stop production until the problem is corrected. If a control strip shows that the control limits have been exceeded, confirm this with a second strip; then refer to the appropriate monitoring manual and stop production until the trouble is corrected. As you continue to plot control values, you will see a random variation around the process mean over which you have little control. As long as the control limits are not exceeded, acceptable quality can be expected. COLOR PROCESS CONTROL CHARTS A good control program uses control charts and subjective print quality analysis in decision making. A control chart provides a tool to avoid situations where a serious processing error is compensated for in printing to keep print quality acceptable. An imaging facility that is compensating for errors near or beyond the control limits is certain to have more quality problems than a facility operating within acceptable standards. Preparing a control chart, such as the Kodak Color Process Record Form, No. Y-55, is quite easy. Follow this 8-step procedure: 1. Use a separate chart for each processing machine. 2. Record the reference strip code number and the reference values in the appropriate places. Use color pencils to distinguish the red, green, and blue densities when recording the reference values. 3. Draw horizontal lines to represent the mean, action limits, and upper- and lower-control limits. 4. Record the process and machine number. 5. When plotting the control values, record the date and time that the control strip was processed (not read), and note any chemical or mechanical changes made as a result of the plots. 6. Plot control values having a plus sign above the line that represents the reference value, and plot control values with a minus sign below the reference value line. 7. Connect the points to provide a continuous graph. 8. When changing to a new control strip code number, note it on the chart. Record the date and the new reference values and limits. The control charts shown in figure 2-18 are not intended to represent an actual control film or process. It is used for illustration purposes only to show patterns that can occur on actual control charts. Processing Control Strips Once control charts are established, control strips must be processed on a regular basis. Each color product has a particular control strip with a particular format. In a sink-line process, a control strip should be processed with each run of production film because of human variables. In continuous (machine) processors, control strips should be processed as follows: Before processing production work at the beginning of the workday, or shift, or after a long shutdown, such as a weekend. Along with production work, at various times throughout the day. At the end of each workday, or shift. After any chemical or mechanical change. Be sure to indicate this change on the control chart. Whenever fresh chemicals are used in the process. Make a note of this on the control chart. 2-34 contents Advanced Photography Course <- previous page next page ->	As an Amazon Associate I earn from qualifying purchases.
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