Stacking Photos to Get the Optimal Effect
In a previous post I discussed how to use ND filters with a long exposure to silken the look of moving water or add a sort of glassiness to water. One of my examples was of Sylvan Lake in South Dakota. I want to expand on that and discuss some possible issues and how to handle them.
Recently I saw a great photo op near my home. This was a tree extending out over a lake. It was on a point with the trunk and limbs literally pointing at about 45 degrees over the water. Knowing what I do about ND filters I knew I could get some pretty cool effects at any time of the day. So I decided to try a long exposure on a mid afternoon June day. I would have never done this a year ago.
The day was fairly windy with about a 20 to 25 mile an hour wind with some additional gusts. This wind created a problem because I wanted some detail in the tree and clouds. A windy day would not hurt a long exposure for the water because I didn't want the detail, but it would definitely cause some unwanted ghosting and blurring in the tree and the clouds. To resolve this problem, I decided to stack two exposures. One exposure for the detail of the tree and clouds and one exposure for the softness of the water. Below are the two individual shots.
For the detail shot on the left I decided to shoot Shutter priority at 1/1000 sec to assure sharpness. To make sure I got what I wanted I also bracketed three exposures at one stop increments. For the long exposure I shot in Manual mode and started at 8 sec and f/16. At this time of the day there was plenty of sunlight, so in order to get the longer shutter speed I had to stop down somewhat on the Aperture. It was pretty difficult to see my shots on the LCD screen so I took some bracketed exposures of these shots as well. There is a little difference in exposure in the two but that shouldn't be a problem. All shots were at ISO 200.
Stacking the images was pretty easy. I started by importing them into Lightroom. Then I found the two I wanted to stack. Remember I was looking for detail in the tree and sky for one and softness in the lake for the other. I also tried to be careful that there wasn't such a difference that blending them would be too unrealistic. It was also important that the two be shot from the same perspective and on a tripod. Otherwise, stacking and blending the images later would be very difficult if even possible. Once I found these images (the two shown above) I used Lightroom's functionality to stack them. Then by right clicking (control click on a Mac) I selected Edit In and then chose Separate Layers in Photoshop. By creating separate layers in Photoshop I could then create layer masks to easily do selective edits.
Photoshop opened with the two images as independent layers, as was requested from Lightroom. The first step was to be sure the two images are aligned with one another. This prevents any kind of ghosting or misalignment issues that would be obvious in the final image. To do this I selected Edit and Auto-Align Layers, then the Auto option. After a few seconds the photos were aligned and I was ready to move on.
With the long exposure as the top layer I created a layer mask for the purpose of removing (masking) the sky and tree to reveal the more detailed image below. Using my Wacom tablet I used light strokes to reveal a small portion at a time. This helped to blend the two images and not make the adjustments obvious.
After the blending was complete I merged the layers and finished the image as I usually do. Here is the final result.
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