Image Errors Introduction

There are many ways that technical faults, file damage and correction errors can appear in images. It is important to be able to identify these problems so that the images can either be corrected, or rejected should the errors be too severe. 

Even if you are not directly involved in digital correction, if you are a picture researcher or picture editor for example, then it is still worth knowing how to identify these images so that their quality can be gauged.   To help make sense of the large range of errors that need to be checked, it is useful to group them into categories.  From there the problems can be sorted into how serious they are. The first division is the list of technical faults, which can be subdivided into external and internal; those that can be checked outside, and those checked inside Photoshop.  What constitutes a technical problem will be determined by your particular workflow.

External technical faults

External faults cover the obvious ones, such as seeing which file format is being used, making sure that there is a file extension, and checking the file size. Not so common are whether the file, or even the embedded colour profile itself, have been corrupted and causing difficulties in opening an image. Other opening problems can be deliberate, such as images having watermarks or file security locks.

Internal technical faults

The list of internal faults is quite wide ranging. They are to do with which colour mode the image is in (CMYK, RGB, etc), whether there is a colour profile attached, the image bit depth, whether the pixel aspect ratio is square or not, the number of channels, if there are any channel masks, quick masks, image layers, the file resolution, and if any sound or text annotations have been attached.  Add to this the File Info panels need to be checked to see if the relevant metadata has been included, or excluded if need be. This is a lot of information to check on.  Fortunately most of this can be automated by either using image quality utilities, or with JavaScript within Photoshop (available since version 7).

The second division of quality faults, and the one with the errors that are more difficult to detect, are those made when the image was captured or corrected. These can be colour problems or image damage, and are covered in the following pages.