After studying this unit you will be able to:

• Understand how to decide about your choice of image capture device 
• Understand how file formats can affect the way your OER is used/shared
• Identify suitable metadata tags for image files

Image capture devices

Image capture devices are the tools used to digitize images.

These could be:

• analog and digital cameras

• document scanners

• analog and digital video recorders

• image capture adapters 

• screen capture and swf file^[1] generation software

Image quality and performance vary between and within devices. Image quality is also affected by hardware (video cards and monitors), software and compression. Once you acquire the basic knowledge of the parameters affecting digital images (pixels, bit depth, file size and resolution, compression), you will be able to compare performances and understand the pros and cons of each type of capture device that will help you make the right decision.

For example, we know that video cameras capture motion and colors rather than resolution, while modern digital still cameras provide excellent resolution. Your choice of device here would be influenced by the intended purpose of the digitised content. Sometimes, though not always the rule, the price of the capture device may correspond linearly with the image quality output from the device.

If you are reproducing an image from printed material, you would use the scanner. Scanning articles can result in very large files because most scanner software by default scan everything as a graphic. The computer has to store information about every dot on the page, not just information about the characters and their placement. You could resolve this by choosing ‘text’ in the save as option if available, or in the .pdf^[2] or use a software tool called optical character recognition, or OCR. This tool recognizes the shape of the letters and gives you a text version of the image.

File formats, proprietary software and compatibility

When an image is digitized, it takes on a specific file format. There are a wide variety of image file formats: some are only recognizable by the program that created them, while others are readable by generic graphic programs. The latter include TIFF^[3], JPEG^[4], BMP^[5], GIF^[6], PICT^[7] and EPS^[8] formats also called open formats. Open formats can be implemented by proprietary^[9] as well as FOSS(Free and Open Source Software)^[10].

Often the choice of file format will affect compatibility. If you wish that others should be able to view, edit and share the image file that you have uploaded this would be possible only with open formats. Proprietary or closed formats prevent reuse, or allow reuse only by the license holders of the software generating these exclusive formats/file extensions.

A number of camera output ‘raw file’ formats can often be proprietary, meaning they could be inaccessible by third party tools/programs.

An open file format is a published specification for storing digital data, maintained by a standards organization(http://en.wikipedia.org/wiki/Standards_organization) which can be used and implemented by anyone. The format is based on an open standard(See http://www.opensource.org/osr-intro for more). The format does not contain proprietary extensions, is fully documented and is publicly available. Examples include jpg, png^[11], svg^[12].

See http://en.wikipedia.org/wiki/Open_format 

Tagging your image with appropriate metadata

Providing appropriate metadata will facilitate access and reuse of your materials.

Try out this group activity on collating metadata:

Select any one of the wiki pages from this module and list the following metadata