Photographing Nashville Warblers
Nashville Warblers have been our most common visitor during this Fall’s migration. Individuals don’t stay long and they are as skittish and unpredictable as most other warblers. I’m always very pleased when I get at least one good, unobstructed shot.
If a warbler pauses for a few seconds and I do get more than one shot, (assuming the flash keeps up with the shutter action) there is always bird movement within the sequence. Warblers don’t sit still, calmly, quietly, motionless. And that makes HDR bird photography impractical.
What HDR Does
Whenever I come across well done, realistic HDR photography on the web, it is most often a promotion for high-end housing or other real estate on the market. A High Dynamic Range (HDR) photo is the compilation of multiple exposures into one and works well with static subjects like fancy interior housing layouts.
The purpose of HDR photography is to capture a careful blend (usually AEB bracketed) of identical images, and then digitally combine them to create a single photo that has a wide dynamic range ..much wider than the camera’s sensor can capture with only one photo.
Why Use HDR?
Photographers practice HDR to enhance tonal richness (expand the dynamic range) of the image. The HDR algorithm incorporated in the camera (or post processing software) pulls multiple images together into one and thus captures more detail on both ends of the 0-256 tonal range spectrum.
Each image file is set up with slightly different exposure settings allowing the camera to create a different dynamic range for each. Most often, the photographer will set up the sequence of shots to use the same ISO, the same aperture, but different shutter speeds. They take the time to measure the shutter speed required for the darkest and the brightest parts of the scene and then add additional shutter stops at the high end and low end. Finally, they blend only those images that expand the tonal range spectrum, i.e. overall dynamic range.
At its best, the HDR process exposes different portions of the final image by different amounts. Called tone mapping, the software allows you to lighten shadows and darken highlights in specific regions. Some photographic artists prefer to use tone mapping to make the blended image look surreal and/or unnatural.
How to Know When to Use HDR
There is no point in considering HDR if the dynamic range of the scene does not exceed the sensor’s light intensity range. It’s easy to check.
Every dSLR camera maps the light intensity range of its sensor on its histogram, so a photographer can instantly determine the dynamic range. If the histogram is ‘clipped‘ at either edge of the scale, picture detail will be lost – either in the shadows (if it’s clipped on the left) or in the highlights (if it’s clipped on the right). If the histogram shows large peaks overflowing at both ends and a low dip in the center, the camera’s sensor can not handle the dynamic range of the subject.
HDR with Bird Photography
Certainly a living, breathing, highly active bird in his natural environment looks much better when the light is outstanding– – when the direction, intensity, and overall quality brings out distinct contrast and eye popping detail.
With HDR, there must be no movement (no discernible heartbeat, no wind, no camera shake) within the sequence of fast continuous shots. In bird photography, there is almost always some evidence of movement between the shots, creating ghosting and alignment issues and making a successful image meld impossible.
Perhaps I should practice on a statue of a bird.