Working Luminance Magic with HDR in Photoshop CS5

Photoshop’s HDR Toning and HDR Pro commands give you unmatched power to finesse tonality in high contrast images, gracefully coaxing detail out of shadows and highlights that would otherwise be murky or blown. Use HDR Toning on single images such as portraits for a faux HDR effect. You can dramatically exceed your camera’s dynamic range by processing multiple exposures of the same scene with HDR Pro. In this tip, we’ll look at how HDR processing works and the HDR Toning command. We’ll continue with HDR Pro in the next tip.

photoshop hdr lead

Today’s tip comes from Chapter 33, High Dynamic Range (HDR Pro), part of Deke’s video course Photoshop CS5 One-on-One: Mastery for lynda.com.

It’s All About Luminance and Space

High Dynamic Range (HDR) processing isn’t about colors, it’s about luminance levels. Photoshop’s HDR Toning and HDR Pro dialogs offer access to the flexible, but somewhat intimidating HDR processing environment. HDR uses 32-bit floating point operations to manipulate tones (luminance + hue + saturation) while minimizing clipping and avoiding banding.

photoshop hdr convert to 32-bit

The 32-bit processing space of HDR contains luminance levels that are whiter than white and blacker than black. The HDR environment also contains many more luminance levels that act as placeholders which fit between the tones available to us when we edit in 16-bit mode. From the standpoint of the 8-bit interface of your computer’s monitor, all of those placeholder luminance levels along with the sub-black and super-white values are invisible, but they serve a powerful purpose; they allow you to move tones in and out of the visible range without losing them. In 16-bit and 8-bit editing, a luminance value that might fall into one of those 32-bit placeholders would simply be clipped to the next lowest available value and lost. This clipping is what produces banding and the gaps that appear in the histogram when you make tonal adjustments in Photoshop.

These are powerful adjustments. It’s a good idea to keep an eye on the histogram to avoid clipping highlights when you accept the dialog and move back into the original bit depth. You’ll want to set up the Histogram panel before you open the modal dialog, because you can’t change its settings while the HDR dialog is open. Set the Histogram panel to Expanded view, with Entire image as source.

photoshop histogram setup

HDR Pro vs HDR Toning

HDR Pro combines luminance values from several exposures of the same scene to build a tone-rich space with a dynamic range exceeding that of your camera. It works something like multi-pass scanning or oversampling in music recording.

HDR toning is the tonal equivalent of upsampling. It cannot produce true High Dynamic Range images, since it starts with just the tones contained in a single exposure. However, it can enhance any single image, often outperforming Shadows/Highlights. It’s a boon for portrait shots, where it’s virtually impossible to get a person to keep perfectly still while you make the bracketed exposures that HDR Pro requires. It is also somewhat easier to get into, so we’ll discuss its application first.

Starting up HDR Toning

To begin editing with HDR toning, select Image > Adjustments > HDR Toning from the menu bar.

HDR Toning will temporarily convert your image into 32 bits/channel mode while you adjust the tones. At the end of the process, it will convert the image back to the bit depth you started with. Layers and Smart Objects cannot survive this process, and the result is a flattened file. However, all is not lost, as we’ll see later.

Photoshop HDR flatten conrirm

If your image contains layers or Smart Objects, you’ll see an alert asking whether you want to flatten the file or cancel the operation. Go ahead and flatten to continue into the HDR Toning interface.

When you first bring up HDR toning, the image can look hideous. The default settings look bad in virtually any image, though they’re not quite as bad as what you see. The preview is only an approximation of the final result, so if you were to accept the settings as-is, the end result would be somewhat toned-down. Still, we can do better.

The toning methods available for HDR procesing are Local Adaptation (the most powerful method), Equalize Histogram, Highlight Compression, and Exposure and Gamma. The effect of these methods, particularly the Local Adaptation presets, behave somewhat differently between HDR Toning and HDR Pro. Equalize Histogram and Highlight compression offer no controls and are not very useful in either.

Using Exposure and Gamma

This option is easy to use once you get used to it. Exposure controls highlights and Gamma controls midtones. There is no control for shadows.

HDR Toning Exposure and Gamma

As tempting as it looks, DO NOT drag the exposure slider around. It’s way too easy to clip highlights or shadows in a heartbeat, even with small maneuvers. Click in the value field and use the up or down arrow key to nudge the value in increments of .1 or use Shift + the arrow keys to bump in increments of .1.

Unlike with the Levels command, increasing the gamma value darkens the image, and decreasing the value lightens it. The arrow and Shift + arrow keys change the gamma settings in the same increments.

The Local Adaptation Method

The real power of HDR is in this method. Most of its presets, though, are not very useful, particularly when used with HDR Toning (they are slightly more useful in HDR Pro). Like Unsharp Mask, High Pass and Shadows/Highlights, Local Adaptation is an edge-detection function. The method creates haloes around parts of the image. Adjustments that focus on specific parts of an image are said to be “local” adjustments, hence the name.

HDR Toning Local Adaptation dialog

A. The Edge Glow section

  • The Radius setting determines the size of halo. Increasing the size spreds it over a larger area, making it harder to detect.
  • The Strength setting is analogous to the Amount value in the Unsharp Mask filter, but it’s not expressed as percentage. A setting of 1 is equivalent to 1%, and the maximum setting of 4, is equivalernt to 4%.

B. The Tone and Detail section

Whenever you see the term “tone,” it refers to a luminance adjustment inside Photoshop.

  • The Gamma slider in this section works the way we’re used to: lowering the value darkens the image, and raising the valud brightens it.
  • Exposure controls the clipping of the white point. You can nudge (up or down arrow key) or bump (Shift + arrow key) the value downward until clipping is eased.
  • The Detail setting controls micro-sharpening. It’s like an adjustable version of the “More Accurate” option in Smart Sharpening. Increasing the value can bring out some very nasty edge artifacts, and decreasing it can produce a strange smoothing effect. In most cases you’ll use the default (3%).
  • Brightening the shadows tends to produce a lot of noise. Sinking the shadows to the lowest value may not go as low as you’d like.

C. The Color section

The Vibrance and Saturation controls go completely over the top very easily. A better approach is to leave those controls flat and mix the result of the HDR Toning adustment with the original. That may surprise you, since we’ve already said that HDR Toning flattens the image. Once you have applied HDR Toning, there is no Fade command available, either. The solution is to use the History panel.

Before we move on to using the Toning Curve section, let’s look at how you make a preset, apply the HDR Toning, and mix the HDR result with the original image.

Save a Preset

  • The small icon next to the preset menu contains the Preset Options menu.
  • Click on it to reveal a fly-out menu and select Save Preset to save your settings. Be sure to save the file in its default location, or it won’t show up in the presets menu.

Apply and Exit

  • Click OK to apply the adjustments and exit the dialog.
  • After you exit the dialog, you’ll have a flattened 8-bit or 16-bit file, depending upon what bit depth you started with.
Photoshop convert HDR

Blending an HDR-toned Layer

As mentioned above, the Fade command is not available after applying HDR. Using the History panel, we’ll grab a snapshot of the HDR-toned history state and convert it into a layer that we can blend with the earlier version of the image.

  1. Activate the History Panel and Alt-click (Mac: Option-click) on the snapshot icon at the bottom of the panel to capture a snapshot.
  2. Assign a name (e.g.“Faux HDR”) and click OK.
    blend HDR step 1
    blend HDR step 2
  3. Now, revert the file to its previous state: Click on the History state directly above the HDR Toning state (or the Flatten Image state if your file had layers prior to toning).
  4. Click in the box on the left side of the Faux HDR snapshot to designate it as the History brush source.
    Blend HDR step 4
  5. Activate the Layers panel and add a blank layer.
  6. Select Edit > Fill from the menu bar.
  7. Set the Use menu to History. (Mode Normal, Opacity 1%, Preserve Transparency un-checked.)
    Photoshop fill history
  8. Click OK
  9. Adjust opacity and blending mode as needed to mix the HDR layer with the original.
    blend HDR step 9

FYI, there is a keyboard shortcut for steps 6-8 above:

  • On Windows, use Ctrl + Alt + Backspace [not Delete!!]
  • On Mac, use Command + Option + Delete

D. Using the Toning Curve and Histogram options

The Toning Curve and Histogram display takes up a lot of space in the dialog. In some cases, the dialog may not be able to expand enough to show the the entire Toning Curve display. If this happens, you can make room by clicking the triangle to collapse the Tone and Detail section.

In most cases, you’ll want to minimize the effects of all other HDR Toning settings when you use the Toning Curve. You can create and save a Neutralize preset with the settings shown:

The interface works like that of the Curves dialog (Image > Adjustments > Curves):

  • Drag in the image to see a bubble that indicates where that tone lives on the histogram.
  • Ctrl-click (Mac: Command-click) to place a point on the curve.
  • Drag or use the arrow keys to position the selected curve point.

Deke’s recommendation: Experiment to find curve settings that work for you. When you do, save them off as presets and then try them on other images.

HDR Toning vs Shadows/Highlights

Deke has explained in other videos for lynda.com that you can create something of a faux HDR effect with Shadows/Highlights. It is a simpler tool to use, but the extra effort of working with HDR Toning generally produces better results.

final couple

Next Time: Working with HDR Pro

That’s it for HDR Toning. Armed with this information, you’ll be amazed at the ways you can open up images where you thoght the shadow detail was hopelessly lost. You can also add subtle refinements to the midtones in ways that dodging and burning can’t match.

We’ll continue this exploration with HDR Pro in the next tip.

Next entry:Deke’s Techniques 021: Assembling a Flawless Panorama

Previous entry:Spirals Reborn in Adobe Illustrator

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