With the simplest explanation depth of field refers to the plane of focus in an image, resulting in areas of sharpness and blur. Depth of field (DOF) can be determined in camera by adjusting the aperture (f-number). Most popularly limited DOF is used to isolate objects from a distracting background. This effect can be faked reasonable simply in Photoshop by several methods. The following method is probably the easiest of those.
Open CTP_TouchUp_DOF.jpg and make a duplicate.
To help the yellow tulip stand out from the background we can apply selective depth of field. Our first task is to separate the yellow tulip from the background.
Select the magic wand tool
On the Options bar select Add to Selection – this will allow us to add to the initial selection. Choose a tolerance of 40 - this lets us select a wide range of tones. Check anti alias to help smooth the edges of the selection and choose Contiguous – which narrows the selection to adjoining pixels.
Start by clicking in the tulip which will make an initial selection
Click on an area that was not selected in the initial selection
Continue clicking until all of the tulip is selected.
To select the stem and leaves, reduce the tolerance amount to around 20. If you select unwanted areas, go to Edit Undo and reduce the tolerance.
Reduce the tolerance again to 10 to select the leaf at left.
Finally zoom in and ensure all of the edges are selected.
Feathering the edges will allow the selection to blend into the image better.. just a tiny feather (which softens the edges of the selection is needed)
Go to Select> Modify >Feather
Choose a small feather of 2
With the selection made CTRL+J to duplicate the tulip onto a new layer.
Now select the background layer and go to Filters>Blur>Lens Blur
The Lens Blur filter dialogue looks complicated. To start with make sure Preview is checked and you can select either faster or accurate – though accurate tends to be much slower.
You can experiment with Shapes - in this instance we choose triangle because that gives us the most blur at the back to a sharper point at the front, as shown roughly below.
Now increase the radius to taste. We will leave the curvature and rotation as is but you can experiment with those options with each image.
Select OK to apply.
The final result has given us a narrower depth of field.
You can download a PDF version of this tutorial by CLICKING HERE
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