Advanced Photography Course

Since it would be impossible to judge whether

densities are reproduced accurately by viewing your
normal production products, special test strips, or
control strips, are prepared. The test strips are
exposed accurately with varying amounts of light.
These test strips are developed in your process, and
the resulting densities are read on a densitometer and
averaged together (fig. 2-1). The densities are then
plotted on a graph. The plot of the data establishes
the standard. Similar test strips are then processed at
regular intervals and compared with the standard to
ensure that the processing is under control. This,
basically, is sensitometry.

Another term used in conjunction with

sensitometry is densitometry. Densitometry is an
integral part of sensitometry. These two terms are
often used together or interchangeably. Technically,
however, there are differences between them. The
differences are as follows:

Sensitometry, or measurement of photographic
sensitivity, is the science of determining the
photographic characteristics of light-sensitive
materials.

Densitometry, or measurement of densities, is
the method whereby data are obtained for
sensitometric calculations.

Measurements of densities are done on a

logarithmic scale. To understand sensitometry, you

must become acquainted with logarithms.

COMMON LOGARITHMS

Complex problems can be calculated easily and

accurately by means of logarithms. You can add
logarithms to achieve multiplication, subtract them to
achieve division, and divide them to derive square
roots.

In photographic quality assurance, logarithms are

used for the following:

Determining density

Plotting characteristic curves

Determining contrast

Determining log H

Reading the densitometer scale

A common logarithm (log

) is an exponent to a

base number of 10. The base 10 is used because our
numerical system is based on units of 10. This can be
demonstrated easily by using scientific notation, or

"powers of 10" For example, the logarithm of 100 is

2, because 10

equals 10 times 10, or 100. The

logarithm of 1,000 is 3, because 10

equals 10 times

10 times 10, or 1,000. Table 2-1 shows how some

common logarithms are computed. Notice the
relationship between the exponent (superscript) and
the common log.

Table 2-1.--Examples of Some Common Logarithms

2-3

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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 -> Since it would be impossible to judge whether densities are reproduced accurately by viewing your normal production products, special test strips, or control strips, are prepared. The test strips are exposed accurately with varying amounts of light. These test strips are developed in your process, and the resulting densities are read on a densitometer and averaged together (fig. 2-1). The densities are then plotted on a graph. The plot of the data establishes the standard. Similar test strips are then processed at regular intervals and compared with the standard to ensure that the processing is under control. This, basically, is sensitometry. Another term used in conjunction with sensitometry is densitometry. Densitometry is an integral part of sensitometry. These two terms are often used together or interchangeably. Technically, however, there are differences between them. The differences are as follows: Sensitometry, or measurement of photographic sensitivity, is the science of determining the photographic characteristics of light-sensitive materials. Densitometry, or measurement of densities, is the method whereby data are obtained for sensitometric calculations. Measurements of densities are done on a logarithmic scale. To understand sensitometry, you must become acquainted with logarithms. COMMON LOGARITHMS Complex problems can be calculated easily and accurately by means of logarithms. You can add logarithms to achieve multiplication, subtract them to achieve division, and divide them to derive square roots. In photographic quality assurance, logarithms are used for the following: Determining density Plotting characteristic curves Determining contrast Determining log H Reading the densitometer scale A common logarithm (log 10 ) is an exponent to a base number of 10. The base 10 is used because our numerical system is based on units of 10. This can be demonstrated easily by using scientific notation, or "powers of 10" For example, the logarithm of 100 is 2, because 10 2 equals 10 times 10, or 100. The logarithm of 1,000 is 3, because 10 3 equals 10 times 10 times 10, or 1,000. Table 2-1 shows how some common logarithms are computed. Notice the relationship between the exponent (superscript) and the common log. Table 2-1.--Examples of Some Common Logarithms 2-3 contents Advanced Photography Course <- previous page next page ->	As an Amazon Associate I earn from qualifying purchases.
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