CHANGE THE DEPTH OF FIELD AFTERWARDS

Here is a little neat trick how you can change the depth of field afterwards.
This can be useful when:
1. You dont’ want to pay 2000 dollars for a lens with an aperture of 1.2.
2. You aren’t able to use big enough aperture when using flashes, for example shooting with an aperture of 2.8 with flashes can be hard.

So here is what we will be doing:
I wrote an article about Understanding Aperture/F stops some time ago where I explain the basics of aperture.
So I thought it would be nice to fake that same image.

So here are 2 photos.
First one taken with an aperture/F stop of 22
Second photo taken with an aperture/F stop of 1.8

And this is what we will be doing:
Same photo as above, only difference is that in the first photo I have faked the depth of field so it looks like it would also have been taken with F/1.8

And here is how it’s done.
Step 1.
Open your photo you want to change the depth of field on.

Step 2.
Above your layers you should have 3 “folders” Layer, Channels and paths.
Go to Channels.
Make a new layer by clicking on the “make new channel” button below the layers.

Step 3.
Choose your Gradient tool, and select your colors so that you have black as you foreground color and white as your background color.

Step 4.
Now use the gradient tool to choose what you want to be in focus and what not to be in focus.
The black color / red color will be show you what is in focus.
So the part where it’s most black/red will be most in focus then fade out to a more blurred background to the right and up (if you are looking on my example).

Step 5.
This is a VERY important step!
You now have to click on your RGB layer inside the channels, so that all your channels EXCEPT the gradient blur layer will be selected.
If you haven’t selected the RGB layer, then the blur won’t work.

Step 6.
Now go to Filter – Blur – Lens blur…
A new window should pop up.
You should now be able tosee from this image which settings I used.

Step 7.
Remove the “eye” from the channels blur/gradient layer.
This will remove the red color and you should be able to see your result.

Here is a quick example how you can use this effect on photos.
I used 2 different flashes in a small room when I took this photo.
Even if I used the minimum power on my flashes I still had an aperture of F/8 or something like that to get the right exposure.
(You can use ND filters on your lens to get bigger apertures too…)

So here is an example how it might have looked like if I would have been able to use an aperture of F/2.8 or something like that instead of F/8.
Same photo as above, but changed the depth of field later on.