How can I create a smooth mask that allows me to multiply the already existing blur?

Question

The question is very simple, and it surprises me I couldn't readily find the solution by googling: I want to reduce the depth of field of a photo in Photoshop. I expected to find something that allows to convert the sharpness of any given area to a smooth mask, so that I can then play with the curves of that mask... but nothing. I only found a "focus peaking" action that uses the high pass filter (very poorly) and tutorials on how to select the foreground image with the lasso -__-'''

What I was hoping for is something that allows me to smoothly simulate a real f/2.8 when the picture was shot at f/5.6. Which means that a binary selection (in focus/out of focus) is no good; I need a smooth mask that allows me to multiply the already existing blur.

Answer 1

If you have PS CS6 then using the Field Blur, Iris Blur or Tilt Shift (blur) filters would be the easiest way. They're great new filters.

Otherwise I would create a new layer, then either:

1. Use a gradient (Foreground color to transparent)

2. Use the marquee tool with a feather pixel edge

   or

3. Simply use a soft brush

to fill the areas which need the 'depth of focus' adjusting.

With the Ctrl key pressed click on the layer thumbnail image to select this area. Then on your image layer adjust your blur to 'adjust' your focus. (You could also do the same as a smart filter if you don't want to lose the original image).

Answer 2

If you consider a vertical figure in a field, some edges are going to be very nearly a binary choice, since anything behind them is on a different plane perpendicular to the film surface, but the field the figure is standing in is going to be a nearly continuous gradient.

When conceived as a greyscale image, the figure would be a cutout and the field would be a 3-point gradient from white to black to white at whatever angle is appropriate for the scene.

You can make both of these items on separate layers (use "transparent" instead of white). ctrl+click one to capture it as a selection, then shift+ctrl click the second one to add that to the existing selection. You can then use this as a basis for a layer mask.

The more complex the scene, the more work must be done, but you can combine any number of mask this way. If you can get it into a grey-on-transparent or greyscale, you can get it into a mask and combine it.

If you use, for example, the lens blur filter, there is an option for using the layer mask as a mask for the blur effect.

I personally don't think there is a (commercially available affordable) programmatic way to pull this off without at least two photos to provide depth data. Without this your eyes and imagination are the next best thing.