Tuesday, October 11, 2011

HDR Isn't Just a Crutch, or a Crime!

Crescent City Sunset, originally uploaded by Jeffrey Sullivan.
Some photographers have fallen in love with High Dynamic Range (HDR) post-processing, producing dramatic but strange results. Other photographers dismiss the often wacky-looking HDR results as "technicolor vomit" and note that any monkey can move a slider in software to make a scene look strange, the talent lies in making a single, flat camera exposure look more like what we experienced onsite. Unfortunately, the range of light present, the dynamic range of the scene, is often far beyond what a single camera exposure can capture. So like so many polarized debates these days, the prudent path may lie somewhere in between.

Take the example below. Often the most interesting and dramatic lighting can be found shooting straight into the sun, but if you expose to preserve the outline of the sun you'll completely lose shadow detail, and if you expose for the shadows, the sun will be an amorphous white area, a clear failure to accurately capture the scene. There are multiple strategies for capturing a scene like this via bracketed exposures, and multiple options for combining those exposures to recreate the scene, but HDR software such as Photomatix can be a fast and easy option, without requiring a lot of detailed manipulation in Photoshop layers.

Mono Lake afternoon reflection (2009 HDR).
Before you focus on post-processing however, it's important to capture useful exposures which really do improve your dynamic range in the shadows and highlights. Bear in mind that your darkest and lightest exposures are not to capture balanced images across the scene, they are primarily to capture detail in the darkest and lightest areas of the scene. Review your dark, medium and bright exposures. Are you capturing the outline of the sun, detail on the moon, or detail in the clouds, sand, water in the darkest exposure? Are you revealing shadow detail in your lightest exposure? If your exposures are not competently recorded, if you leave the bright areas blown out, some percentage of your audience may dismiss your result no matter what you do in post-processing. HDR is no cure-all, no excuse to ignore the basics of photography.

Once you have three competent exposures to work with, the first option in Photomatix that many of HDR's detractors are completely unaware of (and I think many of its users as well) is the ability to simply average the three exposures together. By averaging three exposures, the darkest exposure adds detail from the bright areas "blown out" to white in your center exposure, the lightest exposure adds detail from the darkest, "blocked out" black areas which your center, best single exposure couldn't handle. This useful functionality has been cleverly hidden in the Batch Processing section of Photomatix, and for years now it's been available for use indefinitely in the free trial that you can download from www.HDRsoft.com. Since your'e simply blending together actual light values captured by your camera, much like the iris of your eye captures different exposures as you look around the same scene, the result is a completely natural-looking result, with more range and detail than any single exposure.

Eastern Sierra morning golden hour light (2009 HDR).
The next level of processing available in Photomatix are the various Tone Mapping, Exposure Fusion and Compressor options. Fortunately in the latest versions of Photomatix you can see previews of how these will turn out, and you can pick the best processing option and proceed to fine tune it even more before saving a 16 bit TIFF file with maximum range. Some HDR users stop at this point. But while you can preserve useful detail with these techniques, even when you try to use HDR carefully and in a non-destructive fashion, these processing techniques are pretty intensive and can seriously damage the realism of the scene. Fortunately you can still have the best of both worlds: recover and even enhance detail beyond what a single exposure can handle, and end up with realistic results.

Ellery Lake near Yosemite (2009 HDR).
The next step is by far the most critical, and this is where some HDR users fail to complete the process. The more aggressive HDR techniques can do a good job at enhancing highlight and shadow detail, but used alone, they tend to be lousy at producing a balanced scene with proper contrast, similar to what you'd perceive onsite. The Tone Mapping technique in particular can produce distracting "halos" around objects in your scene that will only serve to scream "rookie" to many viewers. Once you're aware of this you can decrease the strength of the effect as you use the software, but you can also read your 16 bit TIFF HDR result into Photoshop or Photoshop Elements and blend it with your best single exposure edit, or with your Photomatix-averaged exposures to restore much more natural color and light values, while retaining much of the detail enhancement as well. With HDR and realistic (single exposure or averaged) images loaded into two different layers, you can even use Photoshop layer masking to selectively choose areas of the scene which look good in HDR, and select other areas like sky in the non-tone mapped result to simply leave out the blatant halo flaws.

Taking the critical step of blending away HDR flaws doesn't have to be complicated or expensive; if you don't have Photoshop try the layer functionality added into the latest version of Photoshop Elements (about $79.99 in the U.S.). You can download a free trial at www.Adobe.com

3-exposure HDR.  Mono Lake storm (2009).
How do you know when you're done? Think of it like building fine architecture or high end furniture. If the first thing your customers or audience are going to see are nasty sanding marks in the wood, they'll probably think you've blown it, that you have no skill. Similarly, if you can immediately tell at a glance that HDR was used in processing an image, many people will notice the lingering process details before they notice the subject of your image, and that's unfortunate. Weren't you capturing that image to show something other than simply your ownership of a certain tool?

If you can't accurately capture a scene, you'll never get your results into National Geographic. Even if you don't aspire to submit images to them for consideration, it's not all that hard to correct many simple HDR flaws; so why set your sights for image quality any lower?

Now before I set myself up to receive a bunch of hate mail from HDR users, I'm not saying there's anything wrong with uncorrected HDR.  You can produce whatever you want.  Some people are happy with Polaroid images, cell phone images, disposable film cameras and I've taken some of my favorite images on a point-and-shoot digital camera.  People can call anything they want "art," and if they find customers for that, I'm happy for them.  All I'm pointing out is that there is no need to let the HDR process control your results.  You can occasionally demonstrate to your audience that you have skill, that you're in control, even if you choose to stop short of that point and produce artistic, partially-processed results to satisfy HDR fans the rest of the time.  I'd love to see more HDR users develop and demonstrate that skill more often.  Where you go from there is entirely your call.

If you decide to buy Photomatix, you can get a 15% discount by using the coupon code JeffSullivan when you by it from its publisher HDRsoft: http://www.hdrsoft.com/order.php