Exposure & Difficult Lighting – Multiple Exposures

12/27/10 update

Here is an HDR program  “update” that compares results from four leading programs as of 12/11.

Here is an HDR Efex Pro Tutorial

In a previous post, we defined “difficult lighting” and looked at two possible means of dealing with it in-camera while capturing the image. In this section we’ll consider a 3rd alternative which involves shooting multiple exposures followed by post-processing to blend the exposures into a single composite image. The technique is known as high dynamic range (HDR) photography.
I am not going to write a long explanation of HDR photography. Here are two articles to which I can’t add much –

  1. A Wikipedia article
  2. A Readable Illustrated Article

You should understand why & when HDR is your only realistic option for getting well exposed images. After you understand why & when, there are two straightforward steps to take –

  1. Learn to shoot the required multiple exposures in-camera. Look at automatic exposure bracketing in your camera’s manual. You want to shoot (at least) one exposed for the shadows (as covered in the previous post), one for the highlights, and one in between. These exposures should be separated by equal exposure compensation steps. Obviously a tripod should be used and the subject should be stationary.
  2. Learn to combine these in-camera exposures in post-processing. Photomatix Pro is a highly regarded HDR program and a free trial download is available. Photoshop also can be used for HDR processing.The material at the Photomatix site, together with the first article above, tells you all that you need to get started with HDR. Download the trial version and give it a try.

Neither of these two steps are hard to learn. It just takes practice. If you use some of Photomatix’s “canned” options (start with the one called Natural) things go smoothly.
Here are some HDR examples. All done with Photomatix Pro except where noted.
Here are 5 multiple exposures. Aperture priority at -4, -2, 0, +2 & +4 EV.

Below are two examples of the result of processing the above five images in Photomatix.

and the next image shows the best result possible with just a single exposure.

Several observations on the above three images.

  • It is difficult (not impossible) to avoid an unnatural appearance with an HDR image. Of the two above, the left image is not too bad; the right image illustrates the “grunge” effect which many instructors delight in teaching. Better to call this image “digital photographic art” rather than a photograph (personal bias). It’s more like something you’d see in a comic book than in a photography exhibit.
  • The 3rd image has lost almost all detail in the scene beyond the window. Dark areas retain detail but they’re too dark and, when printed, will exhibit high noise content.

Here are several more HDR results.

The first three images represent situations with dark indoors contrasted against bright outdoors. Without HDR (or artificial lighting) these situations cannot be exposed properly. Compare the top row middle image with the similar scene shown in “Exposing for the Highlights” in the previous post. In the current example, indoor detail is retained, but not so in the previous example. The range between dark and light tones in top right (chapel with Grand Tetons through the window) was about as extreme as I’ve done. Absolutely impossible situation for an single ambient light shot.
The bottom two are images that could have been done adequately using the exposure techniques that we’ve already considered – provided that you shot in RAW (always, always, always – did I mention always? – shoot in RAW. More to come later.). The clubhouse fireplace scene would be the more difficult of the two but the artificial lighting will carry the day. As for the landscape, unlike the author of this post’s “must read” introductory article, I rarely (1 in a 1,000) use HDR for landscapes. Armed with Grad-ND filters, a superb RAW processing program, and experience I can usually produce an image that suits my needs better without resorting to HDR. Some photographers start using HDR for everything, even when the histogram is well behaved, and end up using it for a crutch when a properly used Grad-ND filter would do the job as well & usually better. A great “RULE” (this one always applies; never to be broken) – make the in-camera capture as perfect as possible in every respect. Don’t depend on “fixing it in Photoshop”.
The above landscape was done with HDR for illustration. Here is what it looks like with (left) and without (right) the Grad-ND technique (and sans HDR). Here, the filter was applied from right (where the sky is brightest due to the setting sun) to left and not the usual top to bottom. Admittedly the HDR looks more colorful, but that’s not quite reality. It depends on the look you want/prefer. I prefer something closer to reality.

Assignment – Learn to use auto-bracketing; download a trial HDR program (Google around; there are others besides Photomatix including one that I preferred until they went out of business); make and upload an HDR image. Try an indoor + window scene and we can all compare apples & apples with the results. Your home (or the clubhouse) offers lots of opportunities.
Here’s an HDR Update as of 10/17/2010.

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