Extending Your Depth of Field
Sometimes it is just impossible to get everything completely sharp within a photo, even if you stop down to the smallest aperture (such as f22 or f32).
This may be due to using longer focal length lenses (which inherently give us less depth of field), or it could be that you are trying to get something very close AND very far away sharp.
In this example of the Aspen trees, I was using a 200mm lens to visually compress the trees and remove unwanted background. This resulted in a composition where it was physically impossible to get all of the trees sharp. When faced with this type of situation the solution is to shoot several images each focused on different area of the frame and then use Photoshop to blend them together.
The image below shows the three separate images. In the first image, I focused on the front tree. For the next exposure, I focused on the second tree back. The last shot was focused so that the far tree was sharp. Each image was made at an aperture of f16 to spread out the depth of field.
Select the three images in either Lightroom or Bridge. In Lightroom choose Photo>Edit In> Open as Layers in Photoshop. In Bridge choose Tools>Photoshop>Load Files into Photoshop Layers. The image below shows how your new document will appear with the three stacked layers.
Select the three layers by clicking one and then Ctrl-clicking (Cmd-clicking for Mac) on the others. Click the layer where I have it marked with an X. Clicking in other spots on the layer will have a different effect. The image above shows all three layers selected (yellow) Choose Edit > Auto-Align Layers. From the resulting dialog box Choose Auto for projection. Un-check Vignette Removal and Geometric Distortion. Now that your layers are all aligned, Choose Edit>Auto Blend Layers. Choose the Stack Images option and check the Seamless Tones and Colors box as seen below.
Voila! Photoshop has blended your layers together and created a final photo that is sharp throughout. The image below shows the resulting image with the Layers dialog box. Notice that Auto Blend has masked out the necessary areas to create the final image.