LESSON 3
3. Visual quality assurance.
While it is not a scientific procedure,
visual quality assurance can greatly improve the quality of your product.
As its name implies, visual quality assurance involves careful examination
of your product, determining whether it satisfies the requirements of the
work order, and determining its photographic quality. Generally speaking,
you should look for such things as proper contrast, sufficient density, and
the various mechanical and chemical defects.
The best way to examine
negatives is to place them on a standard viewing table. You may also use a
contact printer, but if you do, the same number of lights should always be
turned on. Another simple method for judging a negative is to hold it up to
light being reflected from a piece of white paper.
NOTE: When you examine a photographic image visually, make certain
you are looking at it under normal viewing conditions. Use the same
method each time you make a visual check of quality. Variations in
viewing procedures can result in differing impressions of quality.
a. Negative density.
The negative should have a full range of tones
suitable to the original scene. If it has the proper density, it will have
a wide range of tones all the way from shadows to the highlights.
b. Negative contrast.
The difference between minimum and maximum
densities is called contrast. A good negative will present these densities
in about the same way that the brightness of the various parts of the
subject appear in the scene.
However, negative contrast is a reversed
representation of the original scene contrast.
An exact reversal is not
always desirable.
Sometimes you may want more or less contrast.
By
appropriate manipulation of the process, you can modify the tone rendition
of the original.
c. Mechanical negative defects. These are the defects which cause the
most concern.
They may be caused by improper handling of the sensitized
material, equipment malfunctions, poor techniques, or other things. In most
cases, the cause for any of the following mechanical defects can be traced
directly to the person making or processing the photographs. This list is
by no means a complete one, but it does cover many of the more common
errors.
(1) If the image appears hazy and lacking in contrast, it may be
because:
(a) The sun was shining directly into the lens.
Always protect
your lens from direct rays of sun when shooting against the light.
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