Words and Pictures Peter Bargh
Article updated May 2012.
Choose a landscape photograph with a moody sky. In this photograph of Trethevy Quoit I first added a grey gradient to darken the clouds.
Step 1: Open Your Photo
Open the photo and create a new layer: Layer>New>Layer (Shift+ctrl+N). You can rename the layer if you wish to.
Step 2: Select The Gradient Tool
Select the Gradient tool (shortcut key G) and click on the Transparent Rainbow gradient and the Radial gradient option.
Step 3: Edit The Gradient
Now we need to edit the gradient to give us a thin rainbow. Click on the rainbow in the tool bar. This opens up the edit box. Click on the small green marker on the gradient scale.
Set the location to 50%. Then click on each of the markers to the left and set each one at a single percentage smaller. So yellow on 49%, Red on 48%, Black (above scale) set to 48% too, Grey 47%, white 46%. On the other side set light blue to 51%, dark blue to 52%, pink to 53%, Black (above scale) set to 53% too, Grey 54%, White 55%. You should now have a gradient pattern looking like this.
Give it a name, I called mine Pete's Rainbow, and click New and it will appear at the end of the presets. Then click OK to close the window.
Step 4: Shrink The Photo
Make the photo small in the window (Ctrl + minus key) and make sure the new blank layer is selected.
Step 5: Create The Gradient
With the gradient tool still selected, check that reverse is ticked as we need to flip the colours of the rainbow then click and hold down on the mouse outside the photo area and drag to a lower position and let go. Use the screen grab as a starting point. The idea is to end up with a semi circle rainbow over the photo. You may need to do this a few times until it looks right.
Step 6: Move The Rainbow
Use the Move tool to reposition the rainbow so the bottoms are on the horizon. You can also Use The Free Transform tool to adjust the size of the rainbow.
Step 7: Add Blur
Add a Gaussian blur filter
Filter>Blur>Gaussian Blur and set the pixel radius as high as you can before the colours start to merge into one. About 70 pixels should be okay.
Step 8: Adjust The Rainbow's Size
At this point your rainbow should be starting to look realistic. You may want to repeat the process with a slightly different gradient, buy going back and giving more space to certain colours at the gradient edit step 3. If you're happy you can use the transform tool to pull the rainbow to exactly where you want it to start and end. Edit >Transform>Distort. Click on the lower markers at the edge of the fram and pull the rainbow into position. I stretched both the left and right to take the rainbow into a better position.
Step 9: Add A Layer Mask And Tidy Up The Shot
Last thing to do is tidy up the shot. Add a Layer mask on the rainbow layer and erase areas where the rainbow looks unnatural. On my shot it's where it goes over the quoit and trees. The Brush tool can be set to black or white to paint back or remove the mask. You may also want to lower the opacity of the layer. I set mine to 25% to make it look more blended into the clouds.
Step 10: Save The Image
When you're happy either save the file as a PSD so you can work more on it in the future or flatten and save as a jpg for upload to your web page or printing out.
Words and Pictures Peter Bargh