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Selecting capture device, file format and metadata tags

Page history last edited by Jayashree Balaji 10 years, 4 months ago

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 resolutioncompression), 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

  

Image 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

 

Type of metadata Metadata
Descriptive (title, subject,keywords etc.)  
Administrative (author, version number, license etc.)  
Relational/structural (time period, location etc.)  
Access and publishing(file name, size, creation date, file extension)  

 

 

 

Footnotes

  1. Stands for small web format, a file format for multimedia, vector graphics in the adobe Flash environment.
  2. The Portable Document Format for document exchange.
  3. The Tagged Image File Format is a common type of image file format that contains a variety of descriptive information as well as the image data itself.
  4. A file format named after the Joint Photographic Experts Group who created the standard, it is commonly used file format for compressed(lossy) photographic images.
  5. The bitmap file format for storage of digital images.
  6. The Graphic Interchange Format for storing digital images, commonly used for bullets, icons, and other graphical items on websites.
  7. A graphics file format introduced on the Apple Macintosh computer.
  8. The graphics file format EPS or Encapsulated PostScript is a standard file format for importing and exporting PostScript files.
  9. Proprietary software programs are the legal property of one party.Second or more parties can use them usually under a licensing agreement. The source code of such programs are not made available.
  10. Free and Open Source Software(FOSS) is an inclusive term that covers both free and Open source Software.Free Software refers to freedom to copy and reuse software.Open Source software means the software is available under an open source license with source code and distribution terms(http://opensource.org/docs/osd).
  11. The Portable Network Graphics format designed for transferring images over the web.
  12. The Scalable Vector Graphics file format, an open format for displaying vector graphics on the web.

Comments (3)

Jayashree Balaji said

at 5:51 pm on Apr 30, 2011

From review workshop discussions
some more description of open file formats needed

wayne mackintosh said

at 5:32 pm on Apr 7, 2011

For metadata activity -- suggest sending participants to a image file on the Wikimedia commons which also illustrates metadata

wayne mackintosh said

at 5:24 pm on Apr 7, 2011

We need better description and explanation of open file formats.

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