Tuesday, October 09, 2007

In the lingering light after sunset, it was time to try the impossible

As a change of pace, landscape photographer Steve Kossack likes to stray from the more traditional approaches to landscape photography and work with the subtle light and shadow that occur just before dawn or just after sunset. The choice of capturing the subdued light and mood of these moments sometimes presents unusual challenges...but Steve is well prepared.

"Sometimes it's fun to stretch our abilities," says Steve. "This photo was made after sunset near the Glen Aulin camp in the Yosemite high country during our most recent annual expedition. I noticed others in our group were struggling with this scene’s wide range of light levels which they described somewhat in disgust as an 'impossible' exposure. Agreeing with them, I nevertheless made high-and-low exposures for possible use later in producing a composite image in my computer.

"That was when I decided to apply my 'filter dancing' technique to try capturing this 'impossible' image!

"Let me first explain that--for a time several years ago--I quit using graduated neutral density filters. With the advent of the digital scanner for film images and Photoshop for transparencies, it seemed for a time ND Grads were no longer needed. It seemed I could, instead, simply make an exposure for the highlight areas and another for the shadow areas and then computer-blend them into a composite image. That's the method I used until just a few years ago.

"Then, when I began shooting almost exclusively digital images, I started using my graduated neutral density filters again--but in a new way. Hand-holding my grads in front of the lens was not only quicker and more convenient, but gave me the option of stacking two grads at different angles and moving the stack slightly during the exposure--I call this method 'dancing' with the filters."

When Steve set up for this shot, for example, he first stabilized his Canon IDs II camera on a substantial tripod so nothing could move during the exposure. Although the shortest exposure possible for this situation would “normally” be desirable, Steve went for the longest exposure he could get by using the camera’s lowest ISO setting of 50 and closing the lens to f-16. This resulted in an exposure of 30 seconds which gave Steve more time to “dance” with two 4x6-inch Singh-Ray Graduated Neutral Density filters, a 4-stop hard edge “stacked” on top of a 3-stop Reverse ND Grad. He chose the latter because the “hot spot” was on the horizon and not at the top of the frame. The large, easy-to-grip filters were then moved during the exposure from the top-left corner down to the river’s edge. The motion was repeated several times.

"This is admittedly a non-traditional method," says Steve, "but it's one with few drawbacks and many bonuses. I can easily and quickly shoot dozens of exposures of a scene using the same basic setup. No two exposures will be the same. I found that--when everything works--the mid-tones in the image are brighter and more natural while the shadows have just enough information to show some detail. The highlights still hold the natural feel that sets off the composition. I have also found I can more easily hide the filter gradient line along uneven shapes, like mountains and valleys, making the filters usable where they weren’t before.

Be sure to look at the enlarged version of Steve's image to see how he held the detail in the shadow areas. "I did slightly tweak the exposure curve and saturation of this image, but without the ND Grads, there would have been almost no image to work with, short of spending a lot of time trying to make the composite image look right." Steve adds, "After seeing this single image, I never produced a composite image from the two high-and-low exposures I made. I could judge by what I saw in the two frames that I had managed to get it right in the field with the use of the ND Grad filters...just by dancing."

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