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Lens Blur: depth maps

From: After Effects: Insight into Effects

Video: Lens Blur: depth maps

Now another handy feature of Lens Blur is the ability to use a Depth Map to determine what sections of the image to blur. Let's open up another project of a scene that was rendered from a 3D program and I have also rendered a separate depth map that shows the distance of various objects from the camera. White is closer, black is further away. I will select the image itself, not the depth map, and apply Effect > Lens Blur. I'll crank up the blur a little bit, so you can see what's going on, took it up 20 pixels.

Lens Blur: depth maps

Now another handy feature of Lens Blur is the ability to use a Depth Map to determine what sections of the image to blur. Let's open up another project of a scene that was rendered from a 3D program and I have also rendered a separate depth map that shows the distance of various objects from the camera. White is closer, black is further away. I will select the image itself, not the depth map, and apply Effect > Lens Blur. I'll crank up the blur a little bit, so you can see what's going on, took it up 20 pixels.

And for my Depth Map I will select my special render from my 3D program. This will now cause some objects to appear sharply in focus, in this case the background, another objects to appear out of focus. In other words that grayscale depth map determines what is in or out of focus. I can invert the Depth Map, so instead close objects are in focus and far away objects are out of focus. I can also play around with the Blur Focal Distance. What this parameter does is it determines what values of gray are in focus and then values on either side will go out of focus. For example, if I set this to 120, you'll see that these buildings in the back are in focus, while things in the foreground, or things in the very back are out of focus. If I go ahead and move the focus a bit closer, 180, you'll see that the focus moves so that these objects are now in focus, the closest once are slightly out of focus, and objects behind are also out of focus.

So again, this allows you to add real world camera effects to 3D renders where normally everything would be in perfect focus. Let's go ahead and look at another project. This is another case of a bit more fanciful 3D render. Again I have objects that are rendered in 3D and I have rendered a separate depth map that shows what's close, such as the leading edges of these screens and what's far away. The darker the pixel, the further away it is. I have already got Lens Blur applied, I will enable it, and I'll go ahead and calculate a RAM preview to show you what's like to animate the Blur Focal Distance over the length of this composition. In essence, I'll be pulling focus from near objects to far objects.

Now Lens Blur takes a while to render, so I am going to go ahead and jump ahead to after this render is done. And here is a RAM preview of animating the Blur Focal Distance so objects close are initially in focus and then moves to objects far away being in focus. Another useful application of the Lens Blur effect. Now you might not always have a separate depth map for your scene. It is possible to create a depth map using a Lens Blur. I am going to go back to our first project, where we have this night sky scene, and you notice that the whole scene is blurry. The blue section as well as the stars. This is with Lens Blur turned off.

We can go ahead and pick a layer to be its own depth map. And what you want to do is pick whatever is going to be the best channel to work for depth. So I have my effect turned off, I'll go to my Comp panel and I want to find what color channel provides the greatest contrast between objects that are supposed to be out focus, the stars, and objects are supposed to be in focus such as this blue haze. I'll go ahead and look at the Red channel and it shows me a lot of contrast. The sky drops out to black, all the stars are white. Look at other channels for contrast.

Pick the Green. Hmmm, fair. Blue, almost no contrast at all. That won't be useful at all. The Red channel is going to be my best map. I'll go back to RGB, turn on Lens Blur, choose from my Depth Map Channel the Red channel and crank up my Iris Radius a little bit on my stars. We'll now see that the blue haze is remained in focus, but the stars have gone out of focus. I can go ahead and play around with things such as Specular Threshold to pump up the stars in the final render. Lens Blur off, Lens Blur on, and it does take a moment to render.

Now these show some more realistic applications of the Lens Blur effect. You can also use it for interesting graphical looks. Go watch the movie on Compound Blur. You can do all those same things with Lens Blur, except for Lens Blur is going to look better. And that's a quick overview of Lens Blur. It's a very versatile effect and is particularly useful for visual effects work if you are trying to make scenes look a bit more realistic, particularly ones rendered in 3D. It does take some time to render, and it does take some time to tweak and master, but if you are trying to get perfection, I think it's a good tool to use. And if nothing else, it's a much better version of a Compound Blur effect. So rather than using Compound Blur, you might look at Lens Blur every now and then, just to get a little smoother image.

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This video is part of

Image for After Effects: Insight into Effects
After Effects: Insight into Effects

47 video lessons · 10287 viewers

Chris Meyer and Trish Meyer
Author

 
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  1. 2m 6s
    1. Welcome
      2m 6s
  2. 7m 27s
    1. The Effects & Presets panel: finding effects
      2m 42s
    2. The Effects & Presets panel: animation presets
      4m 45s
  3. 1h 24m
    1. Bilateral Blur
      5m 30s
    2. Box Blur
      5m 33s
    3. CC Vector Blur
      6m 18s
    4. Creative Channel Blur
      2m 2s
    5. Corrective Channel Blur
      1m 47s
    6. The pros of Compound Blur
      4m 35s
    7. The cons of Compound Blur
      3m 3s
    8. Directional Blur
      2m 35s
    9. Fast Blur and Gaussian Blur
      5m 16s
    10. Lens Blur: iris effects
      6m 17s
    11. Lens Blur: depth maps
      4m 41s
    12. Overview of Radial Blurs
      4m 16s
    13. Radial Blurs shootout
      3m 29s
    14. Reduce Interlace Flicker
      4m 12s
    15. Corrective Smart Blur
      4m 26s
    16. Creative Smart Blur
      7m 40s
    17. Unsharp Mask theory
      5m 5s
    18. Unsharp Mask and Sharpen
      3m 59s
    19. Unsharp Mask power tips
      4m 14s
  4. 41m 5s
    1. Overview of Calculations
      3m 55s
    2. Creative Calculations
      3m 32s
    3. CC Composite
      4m 54s
    4. Overview of Channel Combiner
      2m 49s
    5. Channel Combiner and color space
      3m 56s
    6. Channel Combiner and transparency
      4m 0s
    7. Remove Color Matting
      4m 24s
    8. Set Matte vs. Track Mattes
      6m 45s
    9. Set Channels and Shift Channels
      2m 0s
    10. Solid Composite
      4m 50s
  5. 1h 1m
    1. Auto Color vs. Auto Levels
      6m 21s
    2. Auto Contrast vs. Auto Levels
      4m 44s
    3. Channel Mixer
      5m 34s
    4. Corrective Color Balance
      8m 15s
    5. Creative Color Balance
      3m 19s
    6. Color Stabilizer
      4m 51s
    7. Overview of Colorama
      7m 40s
    8. Tinting with Colorama
      5m 48s
    9. Colorama and color cycling
      3m 12s
    10. Hue/Saturation tips
      5m 4s
    11. Hue/Saturation vs. Color Balance
      2m 17s
    12. Tint vs. Tritone
      4m 34s
  6. 14m 40s
    1. Compound effects
      5m 43s
    2. Grayscale shootout
      6m 45s
    3. Repeat Edge Pixels
      2m 12s

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