2013-04-21

Processing a Landscape Image

Exposure

The first exposure I took of this scene (N) looked flat and lacked highlight and shadow detail. It was taken at 1/13th, f5.6 at 100 ISO. I then bracketed the scene -2 and +2 stops to ensure that I would capture the highlight and shadow detail. 

If your scene has more exposure latitude than this, you will need to bracket further. I am not sure why Nikon decided that the maximum bracket is 1 stop on their cameras. They need to fix this!

NOTE: when you are bracketing exposures it is very important that you do not adjust your cameras aperture or move the camera. If you do, the images will not merge properly since the depth of field/focus will vary. You must vary your shutter speed, so it is recommended that you use your cameras Aperture Priority (A or Av) mode. Using a sturdy tripod will ensure that the camera does not move and I also recommend manually focusing your scene.

 Below are the resulting 3 exposures.

HDR

There are many tools available for merging exposures into a single image. Photoshop, Photomatix, HDR Efex Pro, etc. They all perform the same function of blending multiple images into one. This single image is called a High Dynamic Range (HDR) image. A normal photograph is 8 to 14 bits, where as a HDR image is 32 bits.

bits detail per color channel
8 256
12 4096
14 16384
16 65536
32 4294967296

As you can see from the table above a 32 bit image can retain a lot of detail! JPEG images are 8 bits and are optimized for viewing on a computer screen. JPEG images are highly compressed and therefore information is lost and cannot be recovered. This is why it is preferred to shoot in RAW, as that mode captures more detail and the image is not compressed. RAW mode is usually 10-14 bits in most cameras.

Once you produce your HDR image in the tool of your choice you will need to compress the exposure in the scene to something more suitable for editing. This is usually a 16 bit image. In Photomatix one of the common processes for doing this is called tonemapping. Other tools offer other options and effects.

HDR has a love/hate relationship with people. This is because it can get overused and can create some truly scary/awful results. Like most things in photography it is knowing when to use it and how much that make the difference. HDR is a tool and should be used only when required.

Below is the HDR image which has been tonemapped and reduced to 16 bits.
HDR image (tonemapped)

Photoshop

Inside Photoshop you can alter the image as much or as little as you want. I create a new layer for each new effect, and I use adjustment layers whenever I can.

Dodge/Burn Layer

Creating a dodge and burn layer in Photoshop is quite easy and recommended. You can do everything to the image itself, but this way you can undo mistakes with ease. 
  1. Create a new layer
  2. Fill with 50% gray
  3. Set layer blending mode to Overlay
  4. Choose the new layer
  5. Select either the dodge or burn tool
  6. Ensure that the exposure is < 20% and the brush has a soft edge.
Below is the result of dodging and burning the image. I turned off all the other layers so only the dodge/burn layer were visible. Areas that were burned are darker (more exposure) and areas that were dodged are lighter (less exposure). These tools are named after their darkroom equivalents.
Dodge/Burn layer
Original image plus the dodge/burn layer with blending mode set to Overlay.
HDR image plus Dodge/Burn layer
I then created a Levels adjustment layer and created a mask to only affect the sky. I adjusted the levels to bring out detail in the clouds and horizon. I created another adjustment layer and adjusted the color saturation and vibrance of the image. Below is the resulting, finished image.
Final touches (Curves, contrast, saturation)