HDR In Photoshop CS5


Unless you've been hanging out in Antarctica (without an internet connection), you probably know that Adobe has been developing Photoshop CS5 for quite some time. They released this upgrade on April 30th, and one of the most anticipated new features is the program's revamped HDR processing, now called Merge to HDR Pro.

HDR stands for High Dynamic Range, and involves combining three or more exposures of the same scene in order to extend the dynamic range of a photo. While a single exposure can capture detail in a dynamic range of four to six stops, you can extend this range by shooting the same scene at different exposures and then combining the images into one using HDR processing. Prior to CS5, the Merge to HDR feature was cumbersome and lagged behind the more popular Photomatix Pro in its ability to blend exposures together.

In CS5, Merge to HDR Pro is a much simpler process and in my mind can do just as good a job as Photomatix. That said, if you are used to the controls in Photomatix, you will find CS5 a challenge at first, as the controls are different. However, with practice you will find it to be just as easy to use.

In general, good HDR photos start at capture, so to have better success in postprocessing, follow these steps when out shooting:

1. Compose your scene and lock the camera on a tripod.
2. Focus your camera once and then turn off autofocus.
3. Shoot in RAW format for best results. If shooting jpegs, turn off auto white balance.
4. Choose an exposure that will properly capture midtones in the scene.
5. Shoot three exposures, the midtone exposure, then one two stops brighter and one two stops darker. Change your shutter speed, not your aperture.
6. Check your histograms. If your dark exposure is still clipping highlights, take another photo one stop darker. If your brightest exposure is still clipping shadows, take another exposure one stop brighter.

To start the process in Photoshop, use File—Automate—Merge to HDR Pro and choose your files (you can also invoke Merge to HDR from within Lightroom or Bridge). It can take a couple of minutes for the HDR dialog to open, as Photoshop needs to open all of your files, and do the RAW processing. When the HDR window opens, you will see a preview of the HDR image, thumbnails of the original images, and the HDR processing options.

At the top of the processing options, are presets that you can try out to get a feel for what the various sliders do (you can also save your own presets). Next, you will see a checkbox for Remove Ghosts. Check this to eliminate any ghosting created by movement of objects in your scene. When you check this box, you will notice that one of your original image thumbnails is now outlined by a green border. This is the image the program uses as the baseline image for removing any ghosting. Click on a different thumbnail, and the ghosting fix will change based on your new choice. This seems to work pretty well, and puts CS5 a step ahead of Photomatix in this aspect of HDR processing.

Below Remove Ghosts is where you choose the mode. 16 Bit and Local Adaptation are the defaults and generally considered to be the best starting point in Merge to HDR Pro. Most RAW files are 14 bit, so using 32 bit is overkill, and 16 bit gives better tonal changes than 8 bit. Local Adaptation gives you more processing options than the other methods.

Next in line for processing is Edge Glow, with its radius and strength sliders. These sliders let you fine tune any halos present around the edges in the scene. Smaller numbers produce smaller halos, which for most outdoor photography is preferable, especially if you have fine edges set against sky like the tree branches in this photo. Higher numbers, produce bigger halos, and thus a less natural look, though a popular look with some of the HDR crowd.

The tone and detail sliders are where you will balance the tones and determine the detail sharpness in your HDR image. I've found that there is no one group of settings that works well for all images, and this where you will have a bit of a learning curve if you're accustomed to Photomatix. In general, the sliders work this way:

Gamma -
adjusts the dynamic range of the image, with 1.0 maximizing this range. Lower gamma settings emphasize midtones, while higher settings dramatically change highlights and shadows.

Exposure -
does what you'd expect. Higher settings brighten the entire image. Lower settings darken it.
Details - this slider sharpens edges in fine detail areas of the image. It acts kind of like the clarity slider in ACR or Lightroom, except it seems much stronger.

Shadows and Highlights -
these sliders lighten or darken shadows or highlights respectively.

Below the tone and detail sliders are the Color and Curve tabs. if you've been around Photoshop or Lightroom for a while, these are self explanatory. The color sliders lets you adjust vibrance and saturation, while the Curve tab lets you apply a curve to further optimize your HDR image.

You'll probably need to try this out on a few images before you get the hang of it, but it's well worth the learning curve. Of course, this works best when blending several exposures, but Adobe now also gives you the option of creating HDR effects using just one image. For one image HDR processing, open your image file and then go to Image—Adjustments—HDR Toning to bring up the HDR processing options.

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