"Faking" HDR Images
If you already have a picture that you want to make into an HDR photo, you don’t have to go through the process of recreating the image. You can create the HDR effect without having to set up your camera.
1. Open the image that you want to use as your base image.
2. Go to Image and then Adjustment. Select the Shadow/Highlight option. Your values should be close to the following for Shadows:
a. Radius: around 40
b. Shadows: 50 percent
c. Tonal Width: 45 percent.
3. For the Highlights, use the following settings:
a. Radius: around 1,110 pixels
b. Highlight: 80 percent
c. Tonal Width: 75 percent.
4. Create a duplicate layer from the base layer, and select the Color Dodge option for this layer.
5. Duplicate the base layer again, and set the layer to Linear Burn.
6. You may see that certain parts of the image are extremely black. Go to Select and Color Range, and select Invert.
7. Create a New Layer Mask, and select the Gaussian Blur filter.
8. Duplicate the Linear Burn layer, and change the blending option to Overlay.
9. Click on Layer Mask and invert it.