Tuesday, December 7, 2010
Making Best Use Of HDR
Tom Till is a master of Southwest landscapes. Recently, he’s been using HDR software to overcome some of the challenges of these high-contrast scenes without generating the bizarre-looking, hyperreal effect that’s objectionable to many nature shooters
Because I use Photomatix, this sidebar is about my workflow with that program. Recently, a number of other HDR products have come out, but I haven’t tried all of them. On the other hand, I’m very comfortable with Photomatix because I’ve been using it for quite some time.
After loading all my images into Lightroom 3, I start by picking image sets (2, 3, 5 or 7); with higher-contrast scenes, I use more images. I’ve found that high-contrast scenes are more likely to produce images with “artifacts,” areas of strange color or patterns. Sometimes, though, it’s not intuitive. I’ve had better luck just using two images to get a more natural-looking image without all the funny stuff.
The next steps are to export the selected images into a folder and to use the Browse function to select the images for processing. What about image preprocessing? If you’ve entered your lenses into Lightroom 3’s chromatic aberration abatement program, that part is done for you. Since almost all my images going into Photomatix are shot at ISO 100, there’s no need to worry about noise now.
I select my images and press OK. I choose Reduce Chromatic Aberrations, Attempt to Reduce Ghosting Artifacts (usually moving objects), use the recommended color profile and strike Generate HDR. Some HDR experts suggest using noise abatement here, while others suggest to wait until the end and use the new Lightroom/Photoshop system or a Photoshop plug-in. I can’t really see the difference.
Soon a very contrasty image will appear on your screen, mainly because tone mapping is needed to make the dynamic range of your candidate photo suitable for your monitor. By clicking on tone mapping, in a few seconds a (usually) much more suitable photograph appears if your tone-mapping settings are in the default positions I suggest below.
What should these be to produce the most natural-looking image? The more images you shoot, the better you’ll get at managing the tone-mapping controls. To begin with, remember that always leaving the Smoothing control on maximum produces the most realistic image without the Twilight Zone look HDR has been criticized for. I leave the setting there and rarely ever change it.
Next, be careful to watch the HDR histogram, and use the white, black and gamma controls to keep it in bounds. This is the place where your HDR monster gets tamed down to a more normal-range scene.
For my other major controls, I leave Strength at 100, and Microcontrast, which is just a contrast control, at maximum.
Color saturation and luminosity should be accessed for each image. This control works pretty much like the Photoshop/Lightroom versions, except that 50 in Photomatix is akin to 0 here. In an attempt to mimic the colors of Velvia, I usually have my color-saturation setting in the 60-70 range. Luminosity is an overall brightness control, so again, watch the histogram when changing this.
My standard settings on the other controls are Color Temperature, 0; Highlights and Shadows Saturation, 0; all the other smoothness controls are at midrange, and shadow clipping is at 0.
If I notice little gremlins in my image at this point (it usually only happens in deep shadows), I’ll play with a combination of shadow smoothness and clipping to try to eliminate them, and if this doesn’t work, Photoshop cloning or other tools might be needed.
I press Process, and if things look good, I await my image. Nine times out of 10, the image pops out perfectly, and I import it back into Lightroom for cleaning, further noise reduction or other postprocessing needs.
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