Step 1: First of all you need a template.

I decided on a nine blade iris so a nine pointed star and three concentric circles would work just fine.

I chose 400 X 400 pixels as my image size. Using the grid and snap to grid it only takes a few seconds to create the template. Select the 'maximum iris guide' and the 'outside diameter' to and copy them to save time later on. Lets call the first layer 'Guides' and lock it. Create a new layer called 'Blade'. Now draw a pair of small circles as indicated and then paste your copied circle segments in front using Cmnd or Ctrl + F (Mac or Windows). Now change the stroke color to black. One more small circle down at the center and it's time to line up the artwork. Using smart guides, get things tangent.

The 'Center of Rotation' is the axle this blade is going to rotate around. Put a small circle at the center of rotation to act as a guide in AE and lock it.


Now fill your circles with some different colors. About six mouse clicks to go and our shutter blade and the basic AE comp will be complete.

The blue circles will be the three corners of our blade. Select all the artwork and then use the pathfinder tool to divide it into sections. If all your blue circles are tangent with the other circles then you should be able to delete everything except the basic shape of the blade with 6 mouse clicks.


Now select all again (Ctrl or Cmnd A) and unite them. Apply a gradient fill and save the artwork.

Step 2: Now start a new project in After Effects. Import 'Illustrator as comp. . .' and select Blade.ai.

We're ready to start animating. The first thing we have to do is change the anchor point on the Blade layer. It needs to be right over the little black reference dot or 'Center of Rotation.' I like to zoom in to 200% for critical placement.

Drag the anchor point until it's right over the point of the star. Now set key frames for position and rotation on the blade. Move down the time line to 2 seconds. It's time to move and rotate the blade.

You just move the blade down to the next star point and rotate it into position so that the bottom edge lines up with the 'maximum iris guide.' Go back to the start of the time line. We're almost done. Now it's time to Precompose. Make sure you 'Move all attributes to the new composition.' Let's call this precomp 'Blade Precomp'. You'll need to change the composition settings to 600 pixels by 600 pixels so there is plenty of room when you start moving things around.
Here comes a great trick. Open the pre-comp by Alt or Option double clicking on the layer. Now drag the Precomp off to the side so you can see both compositions at the same time. We're going to synchronize both comps so that any changes made in one will be immediately reflected in the other. Go to preferences and choose display.

Click the check box that says 'Synchronize time of all related items.' If you're working on complex projects with lots of related windows this will really slow down the machine, but it's perfect for this kind of project.

Move back to the original composition. We're going to duplicate the blades layer 8 times so we have a total of 9 blades.

Start at the top and rotate each layer 40°. (360° / 9 = 40°) You should see a nice iris form in the comp window. Now it's time to adjust the path of the single blade. Go to the Blade Precomp. Set the time line marker to 1 second. You'll see a problem with the blades.

Click on the Bezier handles as indicated and adjust the path to fix the problem. You'll see that changes in the precomp are visible in the Blades comp window. What a great feature this is.

Your iris should look pretty good by now. A few checks along the time line and some fine tuning of the bezier handles and you should be ready to render. Turn off the 'Guides' layer at this point so you can clearly see what is going on.

I brought in a solid to act as a mask for the outside edge of the iris, added a little lighting effect to the precomp and put a picture of my wife and daughter in for a background. Changing the comp size to 320 X 240 for output and it looks like this.

Not too bad for a genuine simulated nine blade aperture, and a cute kid if I do say so myself.

Rick Gerard,
Gerard Productions
Roseville, California

-- See also Rick's other method of simulating a camera lens aperture using a 3D Sphere Plug-In such as Boris or FE Sphere.

Rick Gerard is a frequent visitor and contributor to the Adobe After Effects COW. Pop in to comment on this article or ask questions. Like to see who Rick is and find other articles that he's contributed? Click here.


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