Combining an image for depth of field
By Rod Barbee
With this image I combined in-field techniques with some Photoshop techniques.
This scene of Upper Horsetail Falls in Oregon’s
Columbia River Gorge, photographed with a 12-24mm lens at 16mm mounted on a
Nikon D300, posed some dilemmas. I wanted a long shutter speed to blur the
waterfall and stream, yet I needed a fast shutter speed to stop the motion
of the wind-blown foreground. To solve this, I took three shots focused at
different points in the scene and then combined them in Photoshop.
It's extremely important that the camera position does not change between
exposures. So be sure you figure out the exposures ahead of time and then
lock the camera securely on the tripod head.
The first parts were easy. I took two shots at ISO 200 (for highest quality)
focusing first on the background and then on the trees in the middle. These
shots were at a f/16 and at about 1 second.
(Actually, I could have probably gotten away with one shot for both the middle
and background)
focused on the cliff
focused on the trees
The foreground needed to be shot at a faster shutter speed, around 1/60 second, to stop the motion blur. This meant a relatively wide aperture. At ISO 200 the shutter speed was still too slow. ISO 640 allowed me to shoot 1/50 second at f/5. This was enough to stop the wind motion of the foreground.
As with nearly all waterfall/stream/forest pictures, a
polarizer really helps with cutting the glare from rocks or leaves, and this
situation was no different. With a regular polarizer, I would have had to
use an ISO of 1000 to achieve the same shutter speed and aperture
combination for the foreground image. But with my
Singh-Ray LB Warming
Polarizer, which is 2/3 stop faster than a regular polarizer, I was able to
use ISO 640. On the D300 there’s not much noise at ISO 640, definitely less
than there would be at ISO 1000. Using the LB Warming Polarizer I was able
to shoot at an ISO that gave me the highest possible image quality given the
situation.
After getting the images into the computer it was just
a matter of layering one on top of the other and masking out the un-needed
parts of each. (for more on layering the separate images, see my
exposure blending tutorial)
Since focus is being changed with each exposure, this means that the
composition is also slightly changed and each layer will be slightly "off"
in alignment. You'll need to use the "Auto Align Layers" command (Edit>Auto
Align Layers) before you start masking.
I also used Imagenomic’s Noiseware for some noise reduction
on the foreground layer. To finish up I cloned out the person under the
waterfall and then used the "Stamp Visible" command (Control-Alt-Shift-E) to
create a layer that is a flattened version of all the visible layers. I used
this layer as a final tune up to adjust colors and bring out some details in
the shadows using the "Shadows and Highlights" command.
Combining these shots was made easier with the guidance of Tony Kuyper’s Digital Scheimpflug tutorial, which involves aligning layers and using masks. Tony Kuyper is a master at creating masks and using them to make powerful and pinpoint adjustments to his images. He’s created a great series of tutorials, most of them free, that will open up a whole new world of image editing for you.
Tony’s website: www.goodlight.us
