I want to simulate depth of field in my photographs. Is the lens blur tool the right tool to do this? Someone told me this would work. I'm struggling with it. Don't understand how to get this channel mask thing to work.
Yes, Lens Blur is the right tool. The basic steps are as follows (filter settings will vary by image):
1. Duplicate the background of the image you wish to apply the filter to, so you can compare or merge the final result with the original if needed.
2. Create a new Channel from the Channels panel.
3. Use the Gradient tool to drag a black-to-white gradient across the image. You may have to make a couple tries at this. Everything that ends up black will be "spared" the filter treatment, everything that's white will have the full filter blurring effect. Gray shades will have varying degrees.
4. Highlight your duped layer and chose the Lens Blur filter.
5. Choose your alpha channel as the Depth Map from the pop-up menu.
6. Tweak the amount and distance sliders first; this will often give a decent result. Make sure you're zoomed in somewhere between 50 and 100%, especially for smaller images. Otherwise you won't be able to see the effect clearly.
7. If the image regions don't appear to blend well you can try the Gaussian Noise option to mimic film-like grain though I personally don't find I need to use this that often unless I'm making a very strong blur.
8. Click OK. The render will take a couple minutes usually. When done you can turn your dup layer on and off to see the difference.
