Article by Peter Bargh. (Updated December 2011).
Pick A Photo
Choose a suitable photo. One taken from a higher viewpoint is better as this is how you would normally view a set-up such as a model railway.
Quick Mask Mode
Open the photo in Photoshop and select Quick Mask mode (shortcut key Q). Now select the Gradient tool (1) making sure the foreground / background colours are set to white / black.
If you've been using different colours press key D to reset. If they are set to black / white press X to switch them.
Select the Reflected gradient (2) and click and hold down the mouse at a central point of the sharp zone, and drag to a point where you want the gradient to end. In the illustration above (point 3) it shows where I dragged from (circle) to the finishing point (tip of arrow) before letting go of the mouse. This covers the non sharp areas in red (the mask)
Press Q to turn off the mask and you will notice that the area that you want sharp now has the selection around it.
If the selection is at the wrong angle or not wide enough hit Q again and redo - the previous mask will be replaced.
When you're happy go to Filter>Blur> Lens Blur. Tick the Invert box to switch the soft focus from the selection to the non-selected area.
Now adjust the Iris section to fine tune the blur effect. For this technique the only slider we need to control is the Radius. Drag out to the left reduces the softer areas and to the right strengthens them. You need to set a radius that softens quite heavily but it's easy to visualise the effect and drag it to a point that looks most realistic. When you're happy click ok and be prepared for short delay as it processes and applies the effect.
You may then want to adjust curves to give the shot more contrast and a plasticy feel.
The shot below is the end result and I've included a couple of other examples of the effects you can achieve.