Exposure Blending

An evening spent at the top of Whitestone Cliffs, Sutton Bank, North Yorkshire in extremely windy conditions, not exactly ideal for low light (long exposure) work! The final blended exposure.

Overview

Often is the case in landscape photography that we want to photograph a scene with a dynamic range that exceeds that of your cameras digital sensor. Your camera will give an image with either over exposed highlights or underexposed shadows. This tutorial will show you how to blend two exposures of the same scene, one exposed for the highlights, the other exposed for the shadows. We will then use Photoshop to blend these two exposures together, creating a single image containing both highlight and shadow detail, see above image (Lake Gormire in red).

 

Taking the images

Once you have found a suitable composition of a high contrast scene, set your camera on a tripod and, if you have one, use a shutter release cable. Set your camera to manual with matrix/evaluative metering selected and make sure it’s set to shoot in RAW mode. Take the first shot exposing for the shadows, do this by checking the histogram on your camera after taking the shot, if the histogram on your camera bunches up to the left adjust the exposure and take another shot making sure the histogram does not bunch up on the left hand side of the scale, see diagram below (Exposed for the shadows). Then take another shot, this time exposing for the highlights by changing the shutter speed by as many stops as is required to move the histogram left until it is no longer touching the right side of the scale, see diagram below (Exposed for the highlights).

 

Exposed for the shadows

 

Exposed for the highlights

 

You should now have two exposures, one will be over exposed, the other underexposed, and we will combine these images in Photoshop by blending them together giving us both, shadow and high detail. The overall effect will be similar to using ND grads in the field (That’s another tutorial!)

Had we taken one exposure the histogram would have looked like the diagram below (shadows and highlights blown), this histogram shows both blown highlights and underexposed shadows.

Shadows and highlights blown

 

Download tutorial files

Download the files below to work through this tutorial or alternatively you can work through your own images. Don’t worry if your finished image is not identical to that of mine.

 

                                                                                           

 

Open the images in your RAW converter and make sure the White Balance is identical on both images. You do not need to make any other adjustments in the RAW converter at this stage and can now open the files (16bit TIFF, 300 DPI) into Photoshop and follow the steps below.

1. Select the highlights image (the darker of the two) and press CTRL + A to select the entire image, then press CTRL + C to copy what we have just selected (the entire image).

 

2. Now select the shadows image (the lighter of the two) and press CTRL + V to paste the highlights image directly on top of the shadows image. You should now have two layers like in the diagram to the left. Hold down ALT and double click the background layer to unlock it and name it Shadows then double click the top layer (layer 1) and rename this layer Highlights.

 

3. At this stage the highlights image has covered the entire shadows image, but we are going to hide the entire layer and paint just the sky part of image in as this is the only part of that layer we require to create a balanced exposure, so select Layer > Layer Mask > Hide All from the Photoshop menu bar, or hold ALT + Click Add Layer in the layers palette menu bar at the bottom.

Now we have both images stacked in Photoshop with the highlights layer hidden, in the next steps we will use the brush tool to paint on the layer mask to reveal only the parts of the highlights image that we need to balance our exposure, in this case the sky.

 

4. Select the brush tool and a large soft brush set to between 10 – 50% (you can adjust the brush size using the [  ] bracket keys Black and white pickeron your keyboard) and set the foreground colour to white by pressing D (see diagram to the left). Now make sure you have the highlights layer mask selected and paint over the sky on the image to reveal the layer. This part is subjective but basically you want to end up with a natural blend revealing the sky and all that beautiful colour, if you make any mistakes you can simply click undo and start painting again or change the foreground colour to black and paint the parts you don’t like back out (almost like using an erasure).

The images below show my final image histogram and layer mask for this image, your final image may differ slightly from the one I have worked on but don’t worry as this tutorial is a basic primer showing what can be done by blending exposures.

Layer mask after painting in the sky.       Histogram after blending both exposures.

Now that we have blended both exposures together we can finish the images off as you would in your usual workflow, I adjusted the final image with a curves and levels adjustment to add some sheen followed by a tweaking of the colour using selective colour before flattening the image and sharpening it for web.

 

The Final Image

 

Closing thoughts

The method above was written to give you a basic idea of the steps that can be taken to help us cover the dynamic range of a scene that exceeds that of our digital sensors, some prefer to use grads while others prefer exposure blending, HDR, etc. I use both, ND grads or/and exposure blending and my aim is to arrive at an image that closely represents that of the one my eyes saw at the time of shooting. While this method only took minutes, some images require far more advanced techniques involving Alpha masks, complex selections and blending techniques of which I will post at a later date for you to work through. I hope this method has opened some creative doors for you and has helped produce better final output images.

 

Links & Further Reading

Michael Reichmann’s similar tutorial over at Luminous Landscape – Understanding Digital Blending