Faux Bokeh – How to blur a Background

Bokeh is that lovely smooth out of focus background.  It can really lift a shot and draw attention  to the subject of the photograph (away from the background).  I always prefer to do it ‘in camera’.  I have four tips for creating strong background Bokeh with your camera.

  1. Use a wide open apperture, f2.8 or greater (smaller number)
  2. Use a Telephoto lens, 100mm or greater
  3. Stand close to the subject – if possible use a Macro lens
  4. Don’t use a camera with a cropped sensor.  The smaller the sensor, the greater the depth of field.

When you can’t do it in camera it’s nice to know how to fake it in Photoshop.  I apologize that this process is rather long and involved.  Unfortunately short cutting the technique will result in tell tale signs that you did it in photoshop.   For instance blur halos can form around your subject.  Have a look at the image below.  There is a blur halo on the left side, but not the right side.  Only subtle, but it can ruin your shot.

Blur Halo

Firstly I will do a quick run through of the principles.  I want to create two new layers, one sharp and one blurred and I will use a mask to indicate where the image will be sharp and where it will be blurred.   I will have to do some work on the blurred layer before I blur it to avoid the blur halo.  I will remove the subject and replace it with something that looks like what the background would be if the subject wasn’t there.

Layers DialogueNow a quick word on layers and masks.  Make sure you have the layers dialog open on the right side of the screen.  This whole process will go wrong if you do the correct step in the wrong layer, or the correct step on the image instead of the mask.  This is the most frequent error with this process.  If it goes wrong just hit the undo button and try and work out which layer and image or mask you are meant to be in.  Each of the following steps will start by telling you which layer we will be working in.

Step 1 – Background layer – duplicate.  (Right click on Background layer in the layers dialog and chose duplicate image) Name the new layer “blurred”

step 2 – Blurred Layer – Selection – use selection tools to trace around the subject of your picture.  Once you are happy with the selection make this into a mask for the “blurred” layer.  Click on the mask creation button.  This is at the bottom of the layers dialog and will look like a circle in a square. (third from the left)  A mask icon should appear along side the “blurred” layer icon.

step 3 – Blurred layer – duplicate. (Right click on Background layer in the layers dialog and chose duplicate image) Name the new layer “Sharp”.  The sharp layer should be on top, then the blurred layer next and finally the background layer on the bottom.  At this point we don’t want to work in the sharp layer – so make it invisible by pressing the eye icon in front of the sharp layer icon.  Do the same for the background layer.

Step 1step 4 – Blurred layer/mask – invert.  Click on the mask icon for the blurred layer so that it has a white square around it.  Go to the menus – Image>Adjustments>Invert.  The black and white of the mask icon should switch places.  Now Apply Layer mask to image – right click on the mask and select “apply layer mask”.  The mask icon should disappear and the subject selection you made previously should become transparent on the layers icon.

Step 2step 5 – Blurred layer/image – content aware fill. Use the magic wand tool to select the transparent area in the middle of your image.  Expand the selection by 5 pixels (Select>Modify>Expand>5).  Now fill the area using content aware fill. (Edit>Fill>Content aware fill).

Step 3

Step 4

Step 6 –  Blurred layer/image – blur.  (Filters>Blur>Gaussian Blur>25)  actually you can adjust the blur according to your preference.

Step 5Step 7 – Sharp Layer – make visible by clicking on the eye in the layers dialog.  You can sharpen this layer if you wish.  I have also done a little contrast enhancement in just the sharp layer.

Step 6There you have it.  It’s not hard to do.  Using this technique you should get convincing bokeh that will not look too fake.

TransformationRefinements.

  • Where the subject edge is blurred you may want to blur the edge of the mask for the sharp layer.
  • Where the background recedes, you may want to have 3 or 4 layers of bokeh , blurred at different diameters to simulate the illusion of depth.

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