Datasheet

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■ FOUR ASPECTS OF BEST PRACTICES
With any of these changes, the technician who made them must work on a copy
of the original, use valid imaging forensic techniques, and be able to repeat them if
required to do so. To enable the repeatability of the process, an audit trail may be used.
An audit trail is the recording of the steps used to make any adjustments so that they
can be repeated to obtain similar results. The audit trail may be a standard procedure
that is routine and consistent, handwritten notes, a text document containing notes, or
data that contains this information stored within the file itself, such as Photoshop’s
History Log.
Some adjustments are basic—such as a brightness or contrast adjustment—and
may always be performed using the same techniques with similar settings. In these
instances, retaining a copy of the modified image and an audit trail of the changes may
not be necessary. The key here is that the procedure is a common one, is a standard
routine, is a valid procedure, and can be easily repeated with similar results—even
without notes. In such an instance, the standard operating procedure becomes the
audit trail.
Audit Trail and History Log
When procedures are used that go beyond basic adjustments, a copy of the modified
image should be retained. And there should be an audit trail of all steps used to make
the adjustments. As mentioned in the preceding section, an audit trail may be hand-
written notes, a text file, or data contained within the image file itself. With Photoshop
CS and above, this can be done automatically using the History Log feature. It is impor-
tant to note that Photoshop’s History Log is not active by default, and must be turned
on in the General Preferences window (Figure 1.1).
Figure 1.1 The History Log must be activated in the General Preferences window.
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