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Tuesday, August 24, 2010

Hi-Tech Studio: Old-School HDR

Long before Photoshop was invented, photographers used graduated ND filters to balance a high-contrast scene. Today, they’re still sometimes the best tool for the job.

This Article Features Photo Zoom

With all of the buzz about HDR software in the last few years,
it can be easy to think that the notion of being able to render a high-contrast scene in a photograph was only addressed when Photoshop came along. The fact is that an older and reliable tool has been around for decades in the on-camera graduated neutral-density filter. Photographers who have been raised in a digital world have a natural tendency to ignore on-camera filters in favor of mimicking their effects with software. There’s no question that digital-imaging tools give you powerful options and those tools can be finely controlled in the computer. Then again, something easily lost in the “fix-it-in-post” mentality is the “fix it” part. Why fix an image when you can get it right the first time, and these simple devices are the most effective tools that photographers have for perfecting an image as much as possible before it ever even lands on a computer.


In this simulated image, you can see how a graduated ND filter can darken the sky in a high-contrast scene.
Grad NDs are the traditional way to do HDR imaging for a reason. You’re compressing the contrast range to a point where it can be rendered by the image sensor and your printer, and you’re doing it by slapping on a filter and shooting. Though computers will provide localized control over an image that’s infinitely more precise, grad NDs give you extensive control from the get-go, not to mention that the time spent digitally correcting a series of images is prohibitive to professional workflows, to say the least.

Grad NDs aren’t necessary for all facets of photography, obviously. You don’t want a strange gradation running through a model’s face, for example, but on the other hand, these filters have evolved over time to suit the particular needs of the subjects that they’re used for the most, often exceptionally well. They’re still an absolutely indispensable piece of equipment to landscape photographers who are frequently shooting at dawn and sunset when the contrast range is at its most difficult.

While one optical filter may not be perfect for every situation, you can be sure that there’s one filter for every situation. Some screw directly onto your camera while others are available as rectangular filters that are held in place by a holder to allow the graduation to be more exact. You can find graduated NDs with soft-edged and hard-edged transitions. In general, soft-edged models should be used when you’re shooting with wide-angle lenses and hard-edged models are better suited to telephoto photography. If you apply a hard-edged filter to a wide-angle lens, you’re likely to see the edge quite clearly, whereas on a telephoto, the transition will be appropriately subtle. Using a soft-edged grad ND with a telephoto can result in almost no effect at all.

Will placing a filter on your camera degrade the image? Yes. Can that degradation be reduced to the point where it’s almost negligible? Yes. Just as with lenses, there are all kinds of optical filters that are made to different tolerances and with varying levels of engineering for optical perfection. A high-quality filter will dramatically reduce adverse effects, and while a good filter isn’t cheap, neither is anything else you rely on to take better photos.


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