Changing the Depth of Field in Photoshop

[Moments Captured]

New to the photography but loving the artistic expression it provides. Would like to know if you can change the depth of field after the picture has been taken? I am currently using Aperture in trial and really like the extent this software allows us to alter our photos. Any comments?

Moments Captured

[McQ]

You cannot *truly* change the depth of field after a photo has been taken since this is determined by the camera's optical system (not software or image processing). However, there are many techniques available for artificially reducing the depth of field using filters in photoshop or other image editing programs.

For decreasing depth of field, the "Lens Blur" tool in photoshop is the first that comes to mind. You will need to selectively apply it to the region you wish to blur by using a layer mask. This is relatively straightforward for images which have two depth layers, comprised of a foreground subject and a background. If there are many objects at various distances, then it can become more complicated and require a blended mask or depth map. However, if all of the layers are tightly intertwined it can become exceedingly difficult to realistically reduce the depth of field using post-processing (such as situations with a lot of foliage or small tree branches close to the camera).

Increasing the depth of field, however, is a different matter entirely. You can use programs that perform what is called a deconvolution to give the appearance of more depth of field. This can only be used sparingly and does not really increase depth of field enormously though. There's a lot more on this in another thread here entitled: Focus magic & other image deconvolution techniques.

Ultimately though, nothing beats getting the right depth of field straight from the camera.

[rc53]

I don't know if this is what you mean; it is possible to combine several images, focussed at different distances, into one with increased dof. The technique seems to find most use in macro pix. But it does need multiple pix which only differ in the focus distance.
Helicon focus are one provider of such software.

[David]

Hi rc53 and Moments Captured

There is also free software called "CombineZM" that carries out the same function of producing an enhance DoF from several images independantly focussed. The first time I tried this I was amazed at the result. However, some skill is required to photograph at appropraite DoF's. To get CombineZM, you're best bet is to Google it, and follow the links.

David

[rc53]

Thanks David; I'll give CombineZM a try.
I did find it was difficult to prevent any subject movement when I tried with Helicon Focus.

Bertie