Friday, December 21, 2007

A close look at High Dynamic Range (HDR) imaging vs. using Graduated ND Filters

Professional outdoor photographer and author Darwin Wiggett provided us with his personal comparison of two popular ways to capture a wider range of brightness levels when photographing high-contrast outdoor scenes with a digital camera. To better compare the images, be sure to click on them for a larger view.

One of the latest techniques arising from the digital era is something called high dynamic range (HDR) imaging. Mostly this is a technique that tries to overcome the biggest shortcoming of digital sensors -- their narrow latitude in capturing different levels of brightness across a scene. Black-and-white and color print film capture a much wider range of tonal values than any digital sensor, and contrast and tonal control is done mostly during printing in the darkroom. Slide film has a tonal range similar to that of digital sensors, and taming contrast is something that is done in-camera using either supplemental light to fill in shadow detail (e.g. fill flash) or filters such as graduated neutral density filters to reduce the brightness of the highlights.

Many digital photographers are intrigued by the idea of HDR capture as a technique that produces images that more closely approximate the way the human eye sees. The most popular HDR software used is Photomatix (www.hdrsoft.com) which is easy to use and generally produces excellent results. To create an HDR image the photographer usually makes three exposures of the same scene, one to capture the mid-tones, one for the highlights, and one for the shadows. Then Photomatix software is used to blend the three exposures into one complete image with a wider tonal range (see Photo 1 above). As you can see, the Photomatix blended photo is colorful, has detail in both the highlights and shadows, and produces an image that most photographers would be happy with.

Of course similar results can be obtained in-camera using graduated neutral density filters (see photo 2 above). To tame the high contrast in this same scene, I simply used a 3-stop soft-edge ND grad that I pulled down over the sky, the mountain and the reflection with the bottom edge of the gradient area positioned just above the foreground rocks. I found the ND grad also does an excellent job of taming the contrast in the scene.

Comparing the two results (Photomatix HDR vs. the ND grad filter) side-by-side, you can see subtle but distinct differences. The Photomatix image has a distinct “HDR look” that is characterized by cartoonish colours and flatter contrast making the image look less dimensional than the grad filter shot. The ND grad filter shot has truer colours, snappy three-dimensional contrast and a ‘feel’ that seems truer to the eye (Photo 2 above).

On closer examination, there are also other important differences between the two techniques. Because Photomatix calls for three or more bracketed exposures, anything that moves in the scene (wind-blown grass, flowing water, floating clouds) will often have ghosting artifacts that simply don’t occur in the single frame grad filter capture (these can be seen by clicking on photo 3 above).

Also the highlights in the Photomatix version are not as crisp and distinct, giving the image a ‘muddier’ look. Photomatix gets the nod, however, for better shadow detail but only in areas where the grad filter darkened the existing shadows (photo 4 above).

In recent months, I have done tests of various scenes using grad filters and the HDR technique. In almost every case, I feel the quality and realism of the images is better with grad filters. There are some scenes where grads can not be used because the grad pattern would be obvious in important parts of the scene (such as this shot), but for 80-90% of my work, ND grads successfully solve my high-contrast imaging issues faster and better than HDR techniques.

The other great benefit of using ND grads is the time saved in post-production. I can process a grad-filtered RAW exposure in about 5 minutes. To do the same shot in Photomatix takes about 20 minutes from start to finish. So ND grads reduce my post-processing time by 75%. That's a huge consideration when I have hundreds of photos to process from a photo trip.

Do I use HDR software? You bet! But I only use HDR when it's absolutely necessary. I will always carry and reach for my grads first. I simply get better pictures, faster, and with less fuss with filters, which in the end means I can spend more time in the field. And that, for me, is the bottom line.

--Darwin Wiggett, DarwinWiggett.com

Wednesday, December 19, 2007

ND Grads plus lots of patience is the name of the game for this photographer

Spokane-based outdoor photographer Ben Chase sends us three images taken earlier this year on 4x5 film in Glacier National Park using his Linhof TK45s view camera.

Regarding this image of Logan Pass, Ben says, "I spent most of an entire day at this same spot on the Hidden Lake trail. While I was planning and composing this photo on my camera's groundglass, a string of passers-by stopped to ask a variety of photo-related questions. I didn't mind discussing their questions since I knew I would have quite a long wait for the right light. Finally, once the distant shadows fell into place, I was able to capture this image just the way I wanted. Because the sky was much brighter than the foreground, a combination of my Singh-Ray Warming Polarizer and a 2-stop Graduated ND Filter did the trick. All told, I spent about 4 hours setting up and waiting for this shot, and I'm pleased that my patience paid off."

Patience was also critical in capturing this next image from Ben. "For three days in a row," he says, "I had tried to get the right combination of mist and color on the mountains in the background at Swiftcurrent Lake. Each day, however, rainy weather and unpredictable winds had stymied my efforts. On the last day of my trip, the weather cleared up and I was able to put my Singh-Ray 3-stop ND Grad filter to good use."

Ben refers to this third image, taken last Spring at Two Medicine Lake, as a good example of why he relies on his Graduated ND filters for at least 70% of his landscapes. "Oftentimes, the right amount and combination of clouds can really make an image more worthwhile. Unfortunately, the clouds and the upper part of the sky can frequently be beyond the exposure latitude of any type of film or digital sensor. When I was taking this image, the combination of a two-stop Singh-Ray ND grad and the Warming Polarizer allowed me to balance the bright sky and capture this pleasant (but windy!) day on the lake."

Working in the field with the 4x5 requires both patience and a smooth workflow. Ben first uses his Sekonic L-558 light meter to measure the exposure range in each scene. "When I find the tonal range is beyond that of my film," says Ben, "I must next decide which ND Grad -- or combination of Grads -- will control the sky. I then hand-hold that Grad in front of the lens with the aperture closed down enough to see the effect on the ground glass. I'm still surprised how well the Singh-Ray ND-Grads hold up against scratches considering the abuse they go through with me hand holding them. For shots I think may be winners, I often bracket my exposures -- which is an expensive proposition with large format film. Fortunately, the number of shots I'm taking per 5 or 6-day trip has now dropped and my 'keep rate' is close to 75%. I just won't break out the gear if I don't think the scene is worthwhile."

A visit to Ben's website will show you many more "worthwhile" images from the Banff/Jasper region of Canada and across the American Northwest.

For a wild 2008...

We just received Daryl Benson's two calendars for 2008, Wild & Scenic Alberta and Canadian Wilderness, and as you might expect, they're filled with stunning images that will help inspire you throughout the year. We haven't asked Daryl for a breakdown of what filters he used for which images, but we have a pretty good idea. Still time to get them for Christmas gift giving, but be sure to get one for yourself, too.

Monday, December 17, 2007

Photo-touring the Middle East puts the importance of filters in a new light

When outdoor photographer Jon Sheppard left his home in Colorado last month to visit Israel and Jordan, he knew he'd be surrounded by history, but he didn't expect such a "monumental" time warp. "Our tour included a fascinating panorama of ancient structures and historic treasures," says John. "At the same time, I found an unexpected range of lighting conditions similar to southern California but without as much rain."

The top photo of the 2,000-year-old Treasury at Petra in Jordan (you may recognize it from the movie Indiana Jones and the Last Crusade) was taken in the morning. "We tried to arrive before the crowds of tourists," says Jon, "but some were there already. The direct desert sun, however, had not yet reached us, so there were no hard shadows to deal with. In this open-shadow light, the only filter needed was my trusty Hi-Lux Warming UV Filter to minimize the haze.

"The middle photo was taken from the restored fortress on top of the historic Masada Rock in Israel overlooking the Judean Desert and the Dead Sea valley. There was considerable haze -- the kind of gray white haze that would hang on for days. The LB Warming Polarizer really made a difference in this light, bringing in much more of the detail in the distance.

"The lower image shows the Great Wall surrounding Old Jerusalem -- obviously weathered by both time and wars. Fortunately, the 90-degree angle of the sun to my right really helped the LB Warming Polarizer bring out the detail in the ancient rock wall.

"During my travels, I tried to think about the light at each scene and decide which filter might work best. Generally, the Gold-N-Blue worked well under hazy and cloudy conditions and the Warming Polarizer worked whenever the sky was clear. On many occasions, I also used my Singh-Ray ND Grads."

Jon is currently adding more photos from his trip to his website jonsheppardphotography.com, so stop by and see what's new.