Photoshop
Tutorial
Tutorial #13
Creating Differential Focus using Quick Mask and the Lens Blur Tool
As I was strolling around the Blists Hill Victorian Town museum in the Ironbridge Gorge, Shropshire, a rather thoughtful employee in period costume posed for me.
Unfortunately there is too much of the background in focus and, being a bit cluttered, it takes away attention from the subject. What we need to do is to keep the subject in focus but create a slight blur to the rest of the image (an effect known as differential focus). To achieve this we are going to use a Photoshop tool called 'Quick Mask' - a very useful selection tool which is, by definition, quick.
Open the image in Photoshop and zoom in so that the subject fills the frame. Then press the 'Edit in Quick Mask Mode' button in the Tool palette.
Click the 'Default Foreground and Background Colours' icon to make sure that the foreground colour is black.
Top Tip !
Just press 'D' on the keyboard to revert to the default foreground and background colours
Click the 'Brush' icon and select a fairly small, hard-edged brush. Here I have chosen a 'hard round 19 pixel' brush.
Carefully paint around the inside edge of the subject.
As you paint, you will see that it colours the area with a semi-transparent red so that you can easily see what is being masked.
If you make a mistake, change the foreground colour to white by clicking the 'Switch Foreground and Background Colours' button and paint over the red with the brush. This will remove the red masking.
Top Tip !
Just press 'X' on the keyboard to switch the foreground and background colours.
Don't forget to change the foreground colour back to black again afterwards.
Continue painting around the inside edge of the subject, then increase the brush size and fill in the rest.
Finally, zoom in and check for errors, swapping the foreground and background colour as necessary to add, or remove, areas of red masking.
When complete, press the 'Edit in Standard Mode' button and your selection will now be surrounded by the familiar 'marching ants'. Note that the subject has been 'masked out' of the selection and so whatever we do to the image now will not effect the subject.
We now want to create a slight blur to the background so select Filter -> Blur -> Lens Blur.
Increase the 'Radius' slider to get the right effect but don't increase it too much otherwise it just looks as if the subject has been pasted on to the background. Press OK when complete.
Press Select -> Deselect to get rid of the 'marching ants'.
So that is now complete. However, I see that his cap is creating a shadow over his face so we will now use the Quick Mask tool to lighten it.
Zoom in, click the Edit in Quick Mask Mode button and paint over his face with a small brush.
When complete, press the 'Edit in Standard Mode' button and then the 'Create a New Fill or Adjustment Layer' button. Then choose 'Exposure.
A new layer will open in the Layers window and the Exposure Adjustment window will also open.
Because we have masked his face though, any exposure adjustment will affect everything else except his face (you can see the Layer Mask Thumbnail in the Exposure layers tab is mainly white with just a black masked area on his face).We want to do the inverse of that so just press 'Ctrl+ I' and you will see the Layer Mask Thumbnail will invert and go mainly black with just a white spot where is face is. Any change to the exposure settings will now just affect his face area.
Top Tip !
To invert (swap) the active part of a Layer Mask press Ctrl-I
Increase the exposure slider slightly to lighten the the shadow on his face.
So now we have a much better version. However, due to the period setting my preference is to go for a monochrome look.
Choose 'Create a New Fill or Adjustment Layer' button. Then choose 'Black & White'.
Adjust the sliders to obtain the optimum result (as detailed in Tutorial 14 - Converting to Monochrome with the Black & White Adjustment Tool).
Here we have the final monochrome version with the subject standing out from the cluttered background - in fact, it looks almost three-dimensional.
Roll mouse over image to see original version
In the next tutorial we will look at converting to monochrome using the Black & White Adjustment Tool.
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