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Seamless Blending Exposures - How to seamlessly blend two different exposures from the same RAW file.
Shooting in RAW format gives you a great deal of flexibility in areas such as exposure and recent developments in techniques such as HDR have taken advantage of this. By combining multiple image exposure made from the same RAW file you can easily open up shadow areas in your images. The downside to HDR is that they can often look false. If you like the idea of blending multiple image exposures but don’t like HDR, here is a simple alternative.
For this tutorial I will use an image I shot in Northumberland where the foreground is too dark and the sky is too light:
Step 1: Create your basic images
Create two images from the same RAW file but with the exposure set to suite different parts of the image. I adjust the first exposure from my RAW file to darken the sky. The second exposure will bring out the detail in the dark seaweed in the foreground.
Exposure 1 – RAW file converted to expose for the sky.
Exposure 2 – RAW file converted to expose for the foreground.
Open both images in Photoshop and select the lighter exposure of the two. Press Ctrl-A [Cmd-A on the Mac] to select the entire image. Copy the selection to the clipboard by pressing Ctrl-C [Cmd-C] or selecting Edit>Copy from the menu.
Step 2: Build the layer file
Now select the darker of the two images in Photoshop and press Ctrl-V [Cmd-V] to paste the lighter image on top of the darker image. You can also use Edit>Paste from the menu. If you check the Photoshop Layers window you should see both images on separate layers, the lighter image being on top.
In the Layers window click the darker of the two images to make it active. Now select the "Channels" tab to display the individual channels. Click on the Blue channel and you should see just the Blue channel displayed in black and white. The reason for selecting the blue channel is that it’s often the darkest of the three in the areas of the picture that need to be lighter.
Step 3: Select your mask
At the bottom of the "Channels" window you will see a row of 4 icons, the first of which appears to be a dotted circle. This is the "Load channel as selection" icon. When you click this you should see the Photoshop "marching ants" appear on screen to indicate the areas of your image have been selected.
In the layers window click on the new layer mask to ensure it is selected. Now press Ctrl-I [Cmd-I] on the keyboard to invert the mask. When you do this you will see your image change as the contrast is dramatically reduced.
Step 4: Adjust your mask
Next we need to adjust the mask to improve the blending. At this point the layer mask should still be selected but if it’s not click on it again. From the Photoshop menu select Image|Adjustment|Levels to display the Levels dialog.
You can now adjust the blending of the two images by moving the centre slider in the Levels dialog to the left or the right. Move it to the left and the light areas of the image get lighter and to the right they get darker.
There are now a few options you can use to improve the blending of your image.
Step 5: Fine tune
Reduce the "Opacity" of the top layer using the Opacity slider in the Layers window. This will allow more of the lower darker layer to show through in the final image.
You can improve the blend as well as making the image appear sharper by applying a small amount of Gaussian Blur filter to the layer mask. Click the Layer Mask to ensure it is selected and then select Filter>Gaussian Blur from the Photoshop Menu. How much blur you apply will depend on the image resolution however a value between 0.5 and 2 is a good starting point.
You can also paint directly onto the layer mask with black or white to adjust the blending. In the example used here the wave in the foreground has also been darkened too much. I can choose to reveal more of the wave in the light layer by painting with a white paintbrush onto the mask. By holding down the Alt key on the keyboard and clicking on the layer mask, you can make the mask visible in order to better see where you are painting. When you paint in this way set the opacity of your paintbrush to around 10% so you can gradually build up the effect.
To help you when you are painting on the mask remember the line "White reveals and Black conceals".
Having adjusted your image use curves to adjust the contrast and brightness and create the final picture.
Tutorial by Robin Whalley.
You've read the article, now go take some fantastic images. You can then upload the pictures, plus any advice and suggestions you have into the dedicated Photo Month forum for everyone at ePHOTOzine to enjoy.