Home Store Project Ideas Project Guide Ask An Expert Blog Careers Teachers Parents Students

Digital Photo Contrast

Difficulty
Time Required Very Short (≤ 1 day)
Prerequisites None
Material Availability Specialty Item: Requires Adobe Photoshop or similar photo editing software
Cost Very Low (under $20)
Safety No issues

Abstract

What do you do if you take a photo and it turns out too dark or too bright? You can use your computer to fix it for you.

Objective

In this experiment you will investigate how changing the contrast of a digital photo will change the colors and quality of the printed image.

Credits

Sara Agee, Ph.D., Science Buddies

Cite This Page

MLA Style

Science Buddies Staff. "Digital Photo Contrast" Science Buddies. Science Buddies, 30 June 2014. Web. 16 Sep. 2014 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/Photo_p006.shtml>

APA Style

Science Buddies Staff. (2014, June 30). Digital Photo Contrast. Retrieved September 16, 2014 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/Photo_p006.shtml

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.


Last edit date: 2014-06-30

Introduction

One of the most common photo edits is to change the brightness or the contrast of a photo. Brightness refers to how much light is in your picture. Contrast is the difference between points of color, called pixels, that are next to each other. The more different the two adjacent pixel colors are, the higher the contrast is. The two highest contrasting colors are black and white.

How can contrast help you make your photo better? Sometimes we take our pictures where there is not enough light. If the picture is too dim you can lighten it by increasing the brightness. The problem will be that as you increase the brightness of the photo, it will start to look washed out. Changing the contrast can correct for this by amplifying the differences in color between pixels in the photo.

Enhancing a photo by changing the brightness and contrast is tricky. You need to strike a careful balance between the two. If you over do the contrast, your picture will look very exaggerated. In this experiment you can investigate the limits of changing the contrast of an image. How low or high can you go before the image quality is compromised? Can you identify the window of opportunity?

Terms and Concepts

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!

  • digital image
  • pixel
  • contrast
  • brightness
Questions
  • How can changing the contrast and brightness settings enhance a digital photo?
  • How does changing the contrast change the quality of an image?
  • How does changing the contrast change the colors of an image?

Bibliography

Materials and Equipment

  • computer
  • Adobe Photoshop or another image editing program that allows you to adjust image contrast. GIMP is a popular free image editing program.
  • your favorite photo
  • color printer
  • photo quality printing paper

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.

Experimental Procedure

Note: the directions are for Adobe Photoshop. If you are using different image editing software, you may need to read the help files or do a web search to find out how to adjust a photo's contrast.

  1. On your desktop, create a new folder called "My Photo Experiment" and place a copy of your favorite photo in the folder (like puppy.jpg).
  2. Open the photo in Adobe Photoshop.
  3. Click "Image" then "Adjustments" and then "Brightness/Contrast" from the file menu.

    How to use Brightness/Contrast
  4. You will see a dialog box that has two slider controls, one for brightness and one for contrast. Click and move one of the sliders, what happens to the image?

    How to use Brightness/Contrast


  5. Next you will make a series of different images with different contrast levels. Set the brightness level to zero for each image. The contrast levels will be set at the following values: -100, -50, 0, +50, and +100. If you want to collect more data, add more settings in between these values.
  6. After changing your first setting, click "OK" to apply the settings and close the dialog box.
  7. Click on "File" and "Save As" to save this picture as a new file in the folder on your desktop named "My Photo Experiment", naming each new file with a different name to keep track of your experiments (like puppy1, puppy2, puppy3, etc.). Keep all of the settings and file extensions the same. You can use a data table to help you keep track of your contrast settings and file names:
    File Name Contrast Setting Description of result:
    puppy.jpg original file  
    puppy1.jpg -100  
    puppy2.jpg -50  
    etc.    
  8. Print the picture on photo quality paper and label the image by writing the contrast setting on the corner of the image.
  9. Close this image and re-open the original image from the desktop folder (puppy.jpg).
  10. Repeat steps 3-9 changing the contrast setting each time, until you have one picture for each setting you wish to test.
  11. Arrange your photos in a row and compare the images. How does contrast change the colors in the photo? Does it change the quality of the photo? When might adjusting this setting be useful?

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.


Variations

  • In this project, you changed the contrast levels. You can also try changing the brightness levels. Do you get similar or different results?
  • To kick this project up a notch, you can quantify the data by counting the number of unique colors in each image. Photoshop can not calculate the unique colors used in an image, so you will need to use another program like PaintShop Pro, which is a shareware program available for a free download. Open each of your files with PaintShop Pro and choose Colors/CountColorsUsed. After a while PaintShop Pro will show a dialog box that tells you the number of unique colors in the image, (like 16,777,216). When you increase or decrease the contrast, what happens to the total number of colors?
  • Another interesting component of a digital image is the saturation and contrast of the image. To investigate these topics see the Science Buddies project ideas Color Saturation and Color Profiles for more ideas.

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.

Ask an Expert

The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

Ask an Expert

Related Links

If you like this project, you might enjoy exploring these related careers:

artist drawing at computer

Multimedia Artist or Animator

If you've ever watched a cartoon, played a video game, or seen an animated movie, you've seen the work of multimedia artists and animators. People in these careers use computers to create the series of pictures that form the animated images or special effects seen in movies, television programs, and computer games. Read more
Girl editing video

Film and Video Editor

Lights, camera, action! It takes more than actors to put an exciting motion picture movie together. It takes film and video editors and cutting-edge computer technology to make an exciting movie that people want to see. From the many thousands of minutes of film and video, the editor has to choose the best shots to tell a cohesive and compelling story. In addition to having an artistic bent, the film and video editor must relish working with complicated computer equipment. If you would like to combine your artistic talents and your computer skills into a great career, then read on to learn more about film and video editors. Read more
Computer programmer typing on a keyboard

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. Read more

Looking for more science fun?

Try one of our science activities for quick, anytime science explorations. The perfect thing to liven up a rainy day, school vacation, or moment of boredom.

Find an Activity