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Project Summary

Difficulty	3
Time required	Very Short (a day or less)
Prerequisites	None
Material Availability	Readily available
Cost	Very Low (under $20)
Safety	No issues

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Abstract

Objective

In this experiment you will test if saving an image file in a different format will change the file size.

Introduction

A digital image file is just like any other computer file containing information. The information is stored as a file of a certain size, depending upon how much information is in the image. The information is stored as bits, and the size of the file is measured in bytes. So the more bits of information you have in your image file, the more bytes of space the file will be. The bits of information in an image file include things like which colors to use, how many colors to use, where to put pixels of color, how many pixels to use, and how big the image is.

All of this information is stored in the file when you save it so that you can open it and use it later. When you save an image file, the program will have you choose a format to save it in. Here are a few of the most common file formats used by most image editing programs:

• JPEG (Joint Photographic Experts Group)
• TIFF (Tagged Image File Format)
• PNG (Portable Network Graphics)
• GIF (Graphic Interchange Format)
• BMP (Bit Mapped)

If the information in the image is the same, then why are there so many different file formats? This is because the information in a file is stored using code. The data is encoded in a different way, depending upon the format you choose. When you open the file, the program reads the code to know how to put the data back together and give you your image.

Why do we need different ways of writing the data into code? One reason is that different image editing programs each have a set of codes that they can open and interpret. One program that can interpret one file format, may not be able to interpret another format. If your file was saved in the wrong format, you may not be able to open it! Another reason is that different codes have different complexities and take up different amounts of space. Some codes are very complex, so they take a lot of processing to interpret and have larger file sizes. This can be a problem if you want to email your photo to a friend. On the other hand, a more simple code that would give a smaller file size might also simplify your data, leading to data loss and a poor image.

What does this all mean when I save my photo? It means you need to match the file format you choose with the way you want to use it. Are you going to email it to a friend, print it out, or put in on a website? Then you can decide the image editing program you will use, the size of file you want and the quality of the image that you need to suit your purpose. In this experiment you will begin to understand how these concepts are related by investigating the link between image file format and file size. After changing the format of your image what will happen to the file size?

Terms, Concepts and Questions to Start Background Research

To do this type of experiment you should know what the following terms mean. Have an adult help you search the internet, or take you to your local library to find out more!

• image file
• file type (TIFF, JPEG, BMP, GIF, PICT, etc.)
• file size (MB)
• image editor
• file save
• save as

• Does changing the file type change the image?
• Are different file types suited for different uses?
• Which file types are best for printing photos? Websites? Email?

Bibliography

• Adobe, 2006. "Adobe Digital Kids Club," Adobe Systems, Inc. [accessed 3/30/06]
  http://www.adobe.com/education/digkids/main.html
• Wikipedia contributors, "Graphics file format summary," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Graphics_file_format_summary&oldid=48844609 [accessed 3/29/06].
• Murray, J.D., and van Ryper, W. 1996. Encyclopedia of Graphics File Formats, Second Edition. Sebastopol, Calif.: O'Reilly.
• Miano, J. 1999. Compressed Image File Formats: JPEG, PNG, GIF, XBM, BMP. Boston: Addison-Wesley Professional.

Materials and Equipment

• computer
• image editor
• your favorite digital photo

Experimental Procedure

1. Choose a photo to use for your experiment. Put a copy of the photo in a new folder on your desktop labeled "Image File Experiment" so it will be easy to find.
2. Open your image editing software. Any image editor will work for this experiment, although the number of options you will have for saving your photo with different image file formats may vary.
3. From the menu bar select "File" and then "Open" by clicking with your mouse.
4. In the browser window, select the new folder you made for your photo on your desktop labeled "Image File Experiment." You should see your picture in the folder. Click on the file name to select your picture and click "OK" or "Choose" (depending upon the software and computer you are using).
5. You should see your photo open in a new window of your image editing program.
6. Now you are ready to save several versions of your file, each as a different type of file by using the "Save As" command from the File Menu. You will want to make a data table to keep track of your results:

   Trial	File Name	File Format	File Size (MB)
   #1
   #2
   #3
   #4

7. From the menu bar select "File" and then "Save As" by clicking with your mouse.
8. In the browser window, find and select the new folder you made on the desktop labeled "Image File Experiment" as the destination for your saved photos.
9. In the "Save As" dialog box there will be a place where you type in a new name to save the new image as. You may change the name of the file, for example you might change a file named "Puppy" to "Puppy1", "Puppy2", "Puppy3", etc.
10. In the "Save As" dialog box there will also be a place where you select the file format you wish to save the new image as. Choose one of the file formats from the list (TIFF, JPEG, GIFF, BMP, EPS, PICT, etc.) and click "OK", "Choose", or "Select" depending upon your program.
11. Another dialog box will appear offering a selection of different settings for the type of image file format you have selected. For this basic project, keep all of these options as the pre-selected default settings. Leave them as they are and do not change anything, then click "OK." (See the Variations section for a more advanced project about changing these settings to optimize your images for different purposes.)
12. The image should now be saved as a new file with a new file format. Write the name of the file and the format of the file in your data table.
13. Repeat steps 6-12 choosing a new and different file format each time.
14. After you have saved your photo in several different file formats, close all of your open images and your image editing program.
15. Open the desktop file manager and select the folder you created to save your photos labeled "Image File Experiment".
16. You will see a list of all of the photos you have saved, along with some other listed information about each file (like the date it was created).
17. In a column to the right you will see a column labeled "File Size." Write the information from this column in your data table next to the corresponding file name.
18. Make a graph of your results. Which file format resulted in the largest file? The smallest file? Were there any file formats that were very similar in size? Can you make recommendations for how or when to use each different type of file?

Variations

• In this experiment you used the default settings for saving your photo in each of the different file formats. For a more advanced project, you can experiment with the different settings for each file format to optimize the settings. How would you change the settings to make a good photographic quality print? How would you change the settings for a website photo? How about for sending a quick email?
• Try opening the files in another image editing program. Do the images open properly? Which files are cross-compatible? Which files are not? Which file format is the best choice for sharing images with people who use different imaging software than you do?
• Do you have a Mac or a PC? Do you use Windows or Linux? Sometimes the file format of an image file is not compatible if transferred across different platforms. If you have access to different computers that run on different platforms, you can test the different image file types for cross-platform compatibility. Which files are most compatible? Which file types are the most specialized?
• How does changing the file type change the quality of the data? You can enlarge each photo saved in each file type and see which ones retain the most data. Will each type of file allow you to enlarge the photo while still looking good?
• There are three main types of color profiles used for printing images: RGB, CMYK and B&W. Try changing the color profile of each type of image to see if it supports all three color profiles. Does the image still look good? Which color profile is the most difficult?

• For more science project ideas in this area of science, see Computer Science Project Ideas.

Credits

Sara Agee, Ph.D., Science Buddies

Last edit date: 2006-08-15 17:14:44

Career Focus

If you like this project, you might enjoy exploring careers in Computer Science.

	Computer Programmer Computers are essential tools in the modern world, handling everything from traffic control, car welding, movie animation, shipping, aircraft design, and social networking to book publishing, business management, music mixing, health care, agriculture, and online shopping. Computer programmers are the people who write the instructions that tell computers what to do.			Computer Software Engineer Are you interested in developing cool video game software for computers? Would you like to learn how to make software run faster and more reliably on different kinds of computers and operating systems? Do you like to apply your computer science skills to solve problems? If so, then you might be interested in the career of a computer software engineer.
	Network Systems and Data Communications Analyst Computers are an important part of our lives. We use computers to hold and process data, to control manufacturing factories, and to surf the Internet. We are all part of many different kinds of computer networks that are continually sharing information. The role of the network systems and data communications analyst is to design, model, and evaluate computer networks so that they can share information seamlessly. This is an exciting career for those people who enjoy working with rapidly changing technology.			Computer Hardware Engineer Whether you are playing video games, surfing the Internet, or writing a term paper, computers are an integral part of our daily lives. Computer hardware engineers work to make computers faster, more robust, and more cost-effective. They design the microprocessor chips that make your computer function, along with the equipment that makes computing easy and fun to do.

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