The Konza Prairie Biological Station is an 8,600 acre tract of tallgrass prairie in the Flint Hills of northeastern Kansas. The Nature Conservancy and Kansas State University own and operate the preserve as an outdoor laboratory to study prairie ecosystems. Fire has been a major influence on prairie ecosystems for centuries and it has been thoroughly studied for four decades at Konza Prairie. Fortunately, burning was being conducted during my visit to Konza last April.
Today’s photograph shows land that was divided by a road into one parcel that was recently burned and an adjacent parcel that remained unburned. The road served as a firebreak during burning.
Prairie grass can grow more than 6 feet tall by the end of good growing seasons. The grass canopy reduces the amount of sunlight and water that reach the soil so new growth is restricted during the following Spring. Burning the canopy early in the Spring promotes new grass growth by allowing significantly more sunlight to be absorbed by the blackened soil. Burning also helps eliminate invasive woody plants.
This scene of today’s photograph was good for black and white photography since it included grass recently blackened by fire, unburned grass that had little color and a colorless gravel road.
Today’s photograph was titled, Firebreak Road, since the primary subject of the photo is the gravel road which served as a firebreak. The natural beauty of the Flint Hills the role of fire in the prairie are secondary subjects.
I was driving through the Konza Prairie and approached a part of the preserve that had been burned a short time earlier. As I reached a hilltop, a beautiful sight revealed itself below. The scene excited me so I hit the brakes and jumped out to acquire a photograph before anything changed. The wind was blowing hard and I thought the exceptional scene justified a small insurance policy for image blur from wind so a duplicate film was exposed.
When finished, I drove down the hill to take a look at the scene from the other end of the road and was even more excited by what I saw. I grabbed my camera gear and scrambled up a nearby hill to get a better view. The scene elements were essentially the same as they were from the other end of the road but they came together better. I decided to expose a third film.
At a scene, I usually identify one primary subject and then try to compose the photograph to emphasize the primary subject as much as possible. The gravel road was the primary subject of today’s photo and I decided to emphasize the road by accenting its four big curves. I thought the road also would be emphasized by placing similar amounts of burned and unburned grass on each side of it.
The closest of the four curves was dealt with first by placing the camera at a location where the road curved into the scene area from the lower left. A fairly long 305mm lens (150mm is a “normal” lens for a 4inch x 5inch camera) was placed on the camera to compress the scene front-to-back to further emphasize curves in the road. Fortunately, the lens covered all four curves nicely and yielded similar amounts of burned and unburned grass on each side of the road.
I took several light meter readings from the scene with a 1 degree spot meter. Dark burned grass on the photo’s left was placed on Zones III-IV (dark with good detail – slightly darker than middle gray) and bright areas of the gravel road fell on Zone VI (slightly brighter than middle gray). N+1 film development was specified to lighten the bright gravel areas by one f-stop to Zone VII (bright with good detail).
The light meter offered several shutter speed and f-stop combinations. A fairly hard wind dictated a reasonably fast shutter speed to prevent blur so I selected a shutter speed of 1/30 sec and an f-stop of f/22-32 (half way between f/22 and f/32).
I was worried that the lens f-stop was not adequately small to achieve sharp focus through the entire scene so the view camera lens was tilted forward to reposition its focal plane more effectively. That is, the slice of sharp focus was tilted from a nearly vertical orientation near the center of the scene to a forward-tilted angle that included the far hilltop as well as the foreground grass at the bottom of the image. View cameras have a definite advantage over other camera designs in situations such as this.
A film was exposed and I drove away.
The three films from this scene were examined with the naked eye and the film which was exposed last looked best, as expected. The 4inch x 5inch black & white film was drum-scanned at my usual resolution of 5,000 ppi and 16-bit pixel depth to obtain a black & white digital image of nearly one GB in size. The digital image that was obtained from the scanner is shown below:
The histogram of the scanned image showed that the full range of gray levels was present (pixel gray levels ranged from pure black to pure white). This might lead one to conclude that the film exposure/development was technically correct since less exposure or more development would have increased clipping in the image. However, the image was very unexciting and communicated little of the emotion that I felt at the scene.
The entire image needed strengthening so a Levels Adjustment Layer was opened in PhotoShop. The two goals of this adjustment were to darken the burned grass and brighten the gravel road & sky. The unexciting emotional content of the image called for relatively large movements of both the black and white sliders of the image histogram. The black slider was moved from 0 (pure black) to 64 and the white slider from 255 (pure white) to 218.
The user interface for PhotoShop’s Levels adjustment is shown below. Dark-to-light tones in this figure progress from left-to-right.
The effect of the Levels adjustment on the image is shown below.
The Levels adjustment caused burned grass to feel more burned, the gravel road to look more like sunlit gravel and the sky to look sunnier. Overall, I was more satisfied with the emotional content of the image after the Levels adjustment.
Every image is different and some are better with no pure black and no pure white pixels whereas others are better with a large number of black and/or white pixels. Today’s image was clearly strengthened by increasing the number of pure black & pure white pixels. That is, the image benefited from significant clipping (pixels that are pure black or pure white) on both ends of the histogram.
When I am in the field my goal is to produce a film that communicates the emotion I feel at the scene. However, mistakes are sometimes made. Emotion was communicated poorly in the film of today’s photo because I placed dark tones too high and developed too little contrast in the film. I should have exposed the film one f-stop less to place burned grass on Zones II-III (very dark with little detail – dark with good detail) rather than Zones III-IV (dark with good detail – slightly darker than middle gray). Similarly, the film should have been developed N+2 rather than N+1 to increase contrast more by brightening light tones.
Fortunately, the problems with the film could be fixed with digital image editing. However, producing more correct images sooner in the photographic process is technically better than correcting problems later in the process.
I often divide an image into different components to help identify things that need improvement. One way to do this is to think of an image in terms of different tonal components. That approach worked well for today’s photograph using PhotoShop’s Curve adjustment.
The curve adjustment user interface is shown below. Note that tonal values progress from light-to-dark beginning at the lower left corner. The figure includes the image’s histogram after the Levels adjustment was performed. The histogram shows that the image is composed of three basic tonal components.
The relatively narrow peak on the left includes bright tones from the sky and gravel road. The broad peak on the right includes dark tones from burned grass. The peak in the middle of the histogram is composed of a pair of peaks with similar gray tones that result from unburned grass. This middle pair more-or-less corresponds to brighter tones of sunlit grass in the left peak and slightly darker tones of shadowed grass in the right peak.
When the histogram for an image contains peaks that correspond to fairly distinct image areas, the opportunity exists to perform a curve adjustment for one or more image areas individually. For today’s photograph, I thought that unburned grass could be visually strengthened by increasing its texture. This could be accomplished by modifying the curve for the middle peak pair in the histogram.
Specifically, the curve shape in the middle of the histogram was changed from linear to an S-shape as shown above. The linear curve was (a) bent upward in the histogram area that corresponded to shadowed grass to darken the shadows more and (b) bent downward in the histogram area that corresponded to sunlit grass to brighten those areas more. This adjustment effectively increased tonal contrast in the unburned grass and had little affect on other areas of the image. The result of this curve adjustment on the image is shown below.
The result of curve adjustment may not be easily seen here since the images shown are so tiny. A 300 KB web image simply can not communicate what is seen in a large print made from a 1 GB file. However, the affect of curve adjustment on unburned grass is readily apparent in large images.
Finally, local retouching was performed using PhotoShop’s Burn, Dodge and Clone tools. The original image layer (image from the scanner) was duplicated, named “Retouch” and placed directly above the original layer to contain retouching edits.
The first area to be retouched was the lower left quadrant of the image where burned grass is brighter than burned grass in other areas of the photograph. Most darker tones in the lower left quadrant were darkened with PhotoShop’s Burn tool and the darkest tones were darkened the most.
That increased texture in the quadrant because darker tones were darkened but brighter tones were not modified significantly. The combination of darkening burned grass in the lower left quadrant and increasing its texture was important for three reasons.
First, increasing texture in the foreground helped communicate front-to-back depth to an image. That is, people expect to visually resolve smaller structures close to them than far away. They use that resolution information as a clue to front-to-back depth in what they are seeing.
Second, viewers unconsciously assign structure near the camera to similar scene areas far from the camera even though detailed structure can not be seen far away. Consequently, increasing foreground texture effectively increases the amount of image structure that viewers perceive through the whole image.
Third, darkening the lower left quadrant increased the visual weight of the burned grass because it produced more similar tones throughout the burned area. That is, darkening the quadrant helped viewers see burned grass more easily as one large burned area.
The following image includes retouching.
The next area to receive retouching was the gravel road. PhotoShop’s Dodge tool was used to lighten the brightest tones of the road. Slightly more lightening was performed in the four major curves of the road to emphasize them.
Next, PhotoShop’s Burn tool was used to darken the photo’s lower right corner and the right half of the photo’s lower edge. These edits were performed to keep the eye from falling off the bottom of the image.
Similarly, two small clouds were darkened to keep the eye from falling off the top of the image. One cloud is located at the upper right corner and the other cloud is located at the top image edge about 1/3 of the way from its left side.
Finally, the image was enlarged substantially on the computer monitor to strengthen individual fence posts. PhotoShop’s Burn and Dodge tools were used to darken dark posts and lighten bright posts.
The tiny web images above can’t easily show the affects of retouching fence posts. Consequently, 4,340pixel x 1,660pixel sections of the full-resolution image were cropped and then reduced to 600pixel x 231pixel images which are posted below. The first image is before retouching whereas the second image is after fence posts were retouched.
Fence post edits increased the overall perception of image sharpness and helped increase the presence of fence lines in the image. You may believe that such changes in small structures do not produce perceivable differences in image quality and that view may be correct when low resolution images are viewed. However, small structural features become more visually perceptible when image resolution increases. My personal photographic goal has always been to produce high quality prints of large size. In my prints, changes like those shown above are important.
This photograph prints nicely and looks best in large sizes where important visual information can be seen.
The overall goal of my photo trip to Kansas was to capture some of the Flint Hills’ natural beauty. I hope that beauty is evident in the photograph discussed today. For a slightly better view of this photo, visit here. To see other photographs of the Kansas prairie, visit my Kansas gallery.
Randall R Bresee