I have been asked this question a number of times about my landscape photographs recently and my answer is absolutely! Landscape photographers do this all the time because of the limitations of the camera. All the great landscape photographers, past and present, use some form of manipulation. Ansel Adams used dodging and burning to change the tonal values of an image. Peter Lik uses a computer to do the same thing.
In my short time as a landscape photographer, I too learned about these limitations of the camera itself is. The camera is one tool used to capture an image. That so called "camera" only sees in mid-tones and does not have the dynamic scale to record all the information in my landscape photographs
The eye can see 24 different shades of light, but the camera can only see 12. On days where the light is even and there are no strong shadows underneath trees or objects, the camera will be able to record everything it "sees." This occurs on cloudy days. On days with bright sunlight and harsh shadows, the camera will only be able to record either the bright information or the dark information only. When a photographer tries to compensate for this in their camera, they can not produce one images that is properly exposed. They can produce two images; One will be a bright picture with properly exposed shadows and the other will be a very dark picture with no detail in the lighter areas. This is the dilemma of a simple, but complicated piece of equipment. So, what is a photographer to do? Blend the images in photoshop.
As a landscape photographer, we can use "photoshop" to compensate for these issues. There are a few ways to do this: 1)The first method would be to underexpose the image a little and then, with photoshop, bring up the highlights and shadows, to create a proper image; 2) The second option is almost the opposite. It would be to bring down the highlight areas and decrease the shadows to create a proper image; These two methods are limited to the amount of information the camera will be able to record. This will produce an image that may contain quite a bit of noise or grain in the image.
There is an additional solution which involves photographing 2 or 3 images and blend them together in photoshop. This is the method that I use.
Their is a method to this madness! First, a photograph is taken of the scene at mid tone levels.. This usually produces an image that has some areas that could be brighter and some areas that could be darker. A second photograph is taken with a proper exposure of the dark areas(usually the foreground). And, finally a third exposure is taken of the brighter areas(usually the sky). Then all three images are added together or blended using photoshop producing an image that represents what my eye saw that early morning or late evening.