Shady Optical Illusion




Here's a simple yet surprising optical illusion that can be made within minutes. It involves four different shades of blue that border each other. The shades go from lightest to darkest when viewed from left to right.

The illusion comes into play when an object is placed along the borders of each successive shade. Something strange occurs with our perception of the obvious difference in shades. In fact, neighboring shades appear to be precisely the same!

Here's a video that showcases the full effect of the illusion:

Step 1: What You Need

Sometimes simple is better. For this project, only the following items are necessary:

1) A sheet of 8.5" x 11" paper
2) Scissors
3) Pencil
4) A program that you can draw in (i.e. Photoshop, Paint, etc.)

Step 2: Creating the Illusion

This is extremely easy to create by using a drawing program. I used Photoshop CS3, but that is entirely unnecesssary. MS Paint is sufficient for this. I will show how I did it in Photoshop.

First of all, open a new project and select the rectangular marquee tool.

Then using that tool just create a rectangle that fills one fourth of the blank project. Fill this in with a very light shade of blue (light cyan specifically). Using the next lightest shade of blue (pure cyan), do the same thing. For the third and fourth quarters of the project, use the next two lightest shades of blue in order (dark cyan and darker cyan respectively).

Now the project can be saved and printed. After printing, cut away the white border around your project. This will eventually enhance the effect of the illusion.

Step 3: Presenting the Illusion

Now that a finished product is in hand, it's time to present the illusion to yourself and/or to others. This is the best part!!

Place the pencil over the transition border between the first two shades of blue on the far left. It will amazingly appear that the first two shades of blue are exactly the same! The same visual phenomenon will hold true when the pencil is moved to the border between the second and third shades. Finally, move the pencil to the transition border between the third and fourth shades. Each time a border is covered, the eye perceives the neighboring shades as being identical. Clearly they are not.

Again, here is the video that shows the illusion being performed. Enjoy!:



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    20 Discussions

    Wow. I can't believe I've never seen this done before. I had a class on optical illusions. This is the best I've seen yet. When you took the last pencil away, I actually watched the colors diverge. 

    I wouldn't be surprised if this was a pre-processing phenomenon, related to the cells near the eye that encode information for the brain. They perform lots of strange compression schemes on all our input data, and many of them are line-based.

    5 replies

    I want to take that class! 

    You may have learned in the class that our brains basically put contrasts ahead of color tones (in terms of priority of processing).  This illusion takes advantage of that when the pencil covers the contrast areas.  Since there is no contrast perceived, we see the same tone when the two tones are just slighty different.  Obviously, when the contrast is then revealed, we can suddenly perceive the difference in tones.  That's the best way I can describe the phenomenon right now.

    Thanks so much for viewing and commenting!

    There is no end to the fascinating world of brain tricks and optical illusions. The most disturbing (or awesome, depending on your POV) optical illusion they showed in class was a video. We were told to watch a short video closely, because something was about to happen. Of about 23 or so people, nobody could tell the teacher what had changed about the image we were looking at (a forest scene). He backed up the scene to the beginning, and there was a river there all of the sudden. By the last frame, there was no river. The damn thing
    dissapeared literally before our eyes. It just became less and less opaque, but it was timed perfectly. Any faster and we would have seen it. It blew our minds.

    The class was called "Introduction to Cognitive Science." We were told that very few schools teach Cognitive Science explicitly. It was the absolute best class I have ever taken. On of my projects was to design the neural architecture of an insect. I recommend taking a class on it, or reading a book about it if you can.


    Cognitive science is so fascinating,  I like to delve into it in my spare time.

    That sounds like an amazing class that you took, and the video you mentioned really sounds neat.  You don't happen to know the name of the video, do you  (or know where or how I could somehow find/watch it )?

    Hmmm...still looking for that video. It's hard to find.


    9 years ago on Introduction

    Wow.  All you do is cover the line. 


    What if you covered ALL the lines?  THAT would be interesting.  I'll try that.

    1 reply

    Reply 8 years ago on Introduction

    Variations of things I see on the web sometimes. Other times, experimentation with colors/shading. Thanks for watching! :)

    Karroo Oakey

    9 years ago on Introduction

    H?uh ..... Please excuse me while I wash my eyeballs. My lenses must be dirty! Good one!


    9 years ago on Introduction


    That is...


    (Can anybody explain this? There must be a huge project on colour-perception in this for any college or university students out there!)

    2 replies

    Reply 9 years ago on Introduction

    (I've got to admit, I didn't believe it at first, so I tested it on the screen with the final image from step 2 and used one of Kitewife's knitting needles to cover the boundaries.)