What about HDR?

08 May

Picture #1, Hopewell Rocks, New Brunswick

Since my blogs are for all levels of audience, some may not know what HDR is. The short description: It’s a technique to fuse two or more images together to simulate what your eyes can see in nature. A bit longer description: Human eyes can see wider luminance range from black to white because the pupils constantly adjust their opening to adapt to ambient light. However, camera sensors cannot sense something that’s too dark or too bright. It’s dynamic range is very limited. So we take two or more pictures, one adjusted to very dark area and another to the very bright area and maybe a few in the middle. All pictures are then layered together to, sort of, present what it’s likely to be seen by our eyes. An even longer description: Well, if you’re really into that, you’d better do some research yourself on the Internet, as I’m not trying to write a thesis here.

(On a side note, you would realize in 2002/2003 Google started being really popular when the word “google” became a verb. “Just google it.” means the same as “Just do a search on the Internet.” in the older days. If Microsoft’s Bing can eventually grab more shares in the search engine market, I would like to hear people say, “Just bing it!” It sounds kind of funny, doesn’t it? “Just bing it!” On the other hand, no one would likely say “Yahoo it.” It’s a two-syllable word, it sounds weird. To be fair, I’m not against Yahoo. Alright, enough of that.)

Picture #2, Hopewell Rocks, New Brunswick

High Dynamic Range (HDR) imaging are getting more popular for two reasons. First, more and more people are buying DSLR cameras, whether traditional DSLRs (Canon/Nikon) or mirrorless (Olympus/Panasonic /Sony etc.) that have exposure bracketing capability. You can also do it with prosumer point-and-shoot cameras if you know how to play with the settings. Even iPhones have the HDR on/off option to give you a taste of what HDR can do.

Second reason is the broad availability of the HDR processing software. Some of them are even free. Before HDR software, the professionals used to manipulate those two or more images in Photoshop to create the final masterpiece. Amateurs would likely be put off by the tedious process. Now with HDR software, since most people are satisfied with the default settings, the process is as simple as just a few clicks on the mouse, and they will have a more pleasing image.

There are people who are against the idea of HDR processing, saying those images are unreal. I understand their point of view as I do see some HDR images on the web that are overly processed, too contrasty and too saturated. Nonetheless, I would keep an open mind. The images were done, one way or another, to please someone’s eyes. Even if it’s not for your taste, there is no need to go over the top and criticize. Below, I posted here a couple of HDR images of my own. For the demonstration purpose, they were a little bit overly processed. But for the three taken in New Brunswick, a more natural setting was used. Therefore, you probably won’t tell they are HDR if posed somewhere else. But as you might have guessed here, they all are.

This set of pictures were taken in Innsbruck, Austria. The first one was just a normal picture anyone could have taken. There is nothing “really wrong” with it. It’s just not “complete”. The second one is 2-stop under exposed. Although the buildings are now darker, it reveals the colorful clouds at dusk. The eyes have no problem seeing all that. But the cameras need two or more exposures to show it all. The HDR software I am using is Photomatix, one of the popular ones. Using the default settings and a few minor tweaks in Aperture 3, here is the final image.

Here is another example of a typical situation in which you need HDR — being inside of a structure looking outward. After taking a picture, you may find either the doorway, or the arch in this case, is too dark or the scene in the distance is too bright. You could only expose for one of them at a time. This set was taken in Dianatempel, Hofgarten (court garden) in Munich, Germany, on a overcast and rainy day.

Left, correct exposure in the middle, but arch is too dark.

Right, 2-stop over exposed, correct exposure for the arch, but the middle part is too bright.

A more desirable image (after HDR processing)

The pros use tripod with cable release to make sure there are perfect alignment across all the shots. For everyone else, some compromises are not a big deal, for you may not have time or convenience to set up all the gears. Yet you still need to ensure 99% of the scene can be overlaid. For this reason only, it’s not enough just activating the exposure bracketing. As I found out myself, the trick is to take advantage of the Continuous Release Mode of your camera, meaning with your hand staying still, holding the shutter release down to take multiple shots in a burst.

And yet, sometimes that’s not enough either. The camera may try to refocus for each shot. It happened to me a couple of times and I couldn’t understand why there were some delays between shots, but finally figured out I had to use manual focus or lock the focus before shooting. One more thing to keep in mind, as with panoramic photos, it’s preferred to use Aperture priority or Manual mode over shutter priority or program mode, so that the depth of field is consistent across all images.

Picture #3, Hopewell Rocks, New Brunswick

Copyright © 2011. Jenson Yu. All rights reserved.
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Posted by on May 8, 2011 in Photography Techniques


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