Using Lightroom’s Photo Merge to HDR

Like many photographers, I am super excited to find about the news of the new Photo Merge>HDR capability in the latest release of Adobe Photoshop® Lightroom® CC. Adobe has designed an especially simple and effective HDR process that takes advantage of Lightroom’s ability to tone map HDR files. In the past we selected our images and exported them to Photoshop to merge the files into an HDR image. Next we would re-import the HDR file into Lightroom and use the powerful Develop module to translate the file into visible tonalities. Now, we can accomplish the whole task with Lightroom itself. Here’s the easy workflow.

  1. In the Library module, select the exposures to blend together.
  2. From the Photo menu choose Photo Merge > HDR…
  3. From the HDR Merge Preview box, choose a Deghost Amount and click the Merge button. (Figure 5.1)
  4. Your newly created HDR file will return to Lightroom with the suffix –HDR.dng
  5. Process the image using Lightroom’s Develop module.

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Figure 5.1 The HDR Merge Preview box

Let’s take each step in their turn. Begin by selecting the images. Click the first image, then Shift-click the last image of the series (this is called a contiguous selection and selects all the images in that series). To select non-adjacent images, click the first image, hold down the Option/Alt key, and continue to click the desired images.

While Lightroom (and most HDR programs) will merge JPEGs, using RAW files is a better choice. RAW files with their high bit depth withstand more severe editing and produce photos with smoother tonal gradations. For this reason, most professional photographers choose to shoot RAW files.

Once the images are selected, go up to the Photo menu and choose Photo Merge > HDR… (Figure 5.2). You’ll notice the keyboard shortcut Control+H listed to the right. For Apple computers, the ⌃ symbol designates the control key.

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Figure 5.2 Choosing Photo Merge > HDR from the Photo menu

 

Your separate exposures are now sent to Lightroom’s HDR Merge function. The HDR Merge Preview Box appears showing you the merged file (Figure 5.1). Adobe has done a great job at keeping this preview box uncluttered and easy to use.

  1. Check the Auto Align box. This function performs just as promised. If your images are slightly out of alignment, this option will attempt to align them. For best results, use a tripod when capturing your exposures. If you are unable to use a tripod, ensure your camera is set to High Speed Drive and Auto Bracket. This will help minimize the difference in alignment.
  1. Checking the Auto Tone check box allows Lightroom to initially set the various exposure and contrast controls. These applied settings are not permanent and can be easily adjusted back in the Develop module. Figure 5.3 shows the Basic panel of a file that had the Auto Tone box checked. To reset the settings to their default values, double click the word “Tone” circled in red in Figure 5.4. For photographers just starting out, keeping the Auto Tone box checked is a good way of learning the various tonal adjustments. Advanced users may wish to keep this box unchecked so they can adjust their images from scratch.
  2. The Deghost Amount is the next option. Ghosting occurs when objects such as blowing leaves, moving clouds or people are in different places in different frames. If blended together without deghosting, those objects appear semi-transparent-ghost like . The process of deghosting, then, is to (1) identify the areas where ghosting may occur and (2) fill in those regions with data from one of the images.
  • The first part of the this process occurs when you choose a Deghosting option. Clicking “None” identifies no areas of ghosting. The “Low” option is fairly conservative in identifying areas that will be ghosted. This means only obvious areas of motion will be identified. The “High” setting is less discerning and will choose more areas that could cause ghosting. Check the Show Deghost Overlay box to see a red overlay where the deghosting will occur. Each time you click another Deghosting option, Lightroom will take a few moments to refresh the preview. Figure 5.5 shows an image with the Low deghosting setting. Figure 5.6 shows the same image with the more aggressive High setting chosen.

 

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Figure 5.3 The Auto Tone settings back in Lightroom

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Figure 5.4 Double click the word Tone to reset all of the sliders back to default positions

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Figure 5.5 The Low deghosting setting in this image picks up almost no ghosting

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Figure 5.6 The High deghosting setting identifies more motion in the leaves in the center

 

  1. The second part of the deghosting process happens behind the scenes. After choosing a deghosting setting, click Merge at the bottom of the HDR Merge Preview box to begin the processing. At this point the Low, Medium, and High settings don’t make a difference. Lightroom is now filling each identified region with image data from one of the uploaded photos. The source for each region is chosen to minimize noise without clipping the highlights. Unlike Photomatix, we have no choices at this stage. Simply click Merge and Lightroom performs its magic.

 

Once you click Merge, the preview box disappears and Lightroom begins processing your image. Progress is marked by the task bar in the upper left corner of the screen (Figure 5.7).

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Figure 5.7 The task bar in the upper left portion of the program

The newly created HDR file can now be found in the folder with the source images. Look for it next to the last or first image in the group. In Figure 5.8, you see the new file is named DSC_3179-HDR.dng. Lightroom automatically took the last file name in the series and added a hyphen and HDR. This makes it easy to differentiate from the surrounding files. You’ll also notice that the new image is a .dng file, which is Adobe’s RAW file format. This is a great new feature in Lightroom’s HDR workflow. Most (if not all) HDR programs will return either a .tif or JPEG file.   Returning a 16-bit .tif file is fine when the tonemapping/tonal adjusting is occurring in the HDR program. This means that most of the heavy lifting has already been done. When blending with Lightroom, however, the Merge command is simply including all of the tones of the various source images into one file. This HDR.dng image is now ready for tonal adjustments back in the Develop panel.

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Figure 5.8 The newly created HDR.dng image is selected back in the Library module.

 

Note:

I prefer having the image name above the thumbnail in the grid view to easily identify my photos. Because Lightroom does not include this information by default, you have to alter the View Options. Tap the keyboard letter G to take you into the Grid View of the Library Module. Next choose View > View Options. Choose Show Grid Extras: and Expanded Cells (circled in red in Figure 5.9). Under Expanded Cell extras, check Show Header with Labels and from the drop down choose File Name. The rest of the box is also set up in a manner that makes it easier to identify and work with your images. Experiment with these settings to see if they fit your needs.

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Figure 5.9 The Library View Options box.

 

Developing Your HDR file

The fact that Lightroom returns a .dng file makes for a very flexible workflow. This means it is unnecessary to make any changes to the images before merging them. Every possible edit you can perform before merging can be performed after. When using Lightroom to Merge, I prefer to leave my images un-edited before blending. Once the HDR.dng returns, I treat it as I would any other raw image. As mentioned earlier, there are several edits I perform on just about every image: Clarity, Sharpening, and Chromatic Aberration.

If you chose Auto Tone back in the HDR Merge box, your image may already look pretty good. If you unchecked the box, you may see an image that shows very little or no shadow detail (Figure 5.10). No problem. The HDR file contains plenty of information that the sliders in the Basic panel can retrieve.

  1. In Figure 5.11, I have adjusted the Exposure up to +1.20 and the highlights down to -100. Think of the Exposure slider as a brightness adjustment. Are you midtones to dark? Raise the Exposure slider. Too light? Lower the Exposure slider. Here the image contains highlight detail but is overall a bit dark.
  2. As you raise the exposure slider, you are likely to see the highlights start to overexpose. Increase the Exposure slider until the midtones are satisfactory and then lower the Highlight slider. If the Highlight slider goes to -100 and the highlights are still blown out, you may need to lower the Whites slider. Care should be taken with lowering the Whites slider, however. Decreasing this control too much reduces the overall impact of the photo. Take a close look at the histogram. Notice how the highlights are retaining detail without being overly dark. It’s important to keep a bright white with detail in most photographs.
  3. The midtones and highlights now look good, but the shadows are still a bit dark. In Figure Figure 5.12, I raised the Shadows slider to +89. This move makes shadows look good but now I lack a deep black. Just as its important to keep a bright highlight, its also important to keep a nice rich black.
  4. Next I move my blacks down to -53 to anchor the blacks. Don’t be afraid to clip the blacks. Let there be some black without detail in your images. The last tonal adjustment is an increase in the whites to +8 to ensure a crisp bright white. The Histogram in Figure 5.13 shows the whites coming right down into the corner, and some clipping in the blacks, but well within our tolerance.

The Tonal adjustments should always be made first, as they have a significant effect on saturation. Increasing exposure and whites and decreasing blacks is another form of adding contrast into an image. Adding contrast to an image always increases saturation. The engineers at Adobe placed the Saturation slider at the bottom of the panel so that we adjust the tones before we adjust the saturation.

As you might realize, making adjustments as dramatic to these to a typical RAW image or a JPEG could really reduce the image quality. Because this is a RAW file created from an HDR merge, though, the file remains pristine.

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Figure 5.10 Unadjusted HDR.dng file in Lightroom’s Develop module

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Figure 5.11 Increasing the Exposure up to +1.20 and decreasing the Highlights down to -100

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Figure 5.12 Raising the shadow slider to +89

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Figure 5.13 Adjusting the Blacks down to -53 and increasing the Whites to +8

 

For this next example we’ll blend together six exposures made in a tunnel in Bruges, Belgium (Figure 5.14 ). Our eyes perceive this tunnel as dark, with a very bright courtyard. Our adjustments back in Lightroom need to enhance this perception while still providing important detail.

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Figure 5.14: A series of six images to be blended using Lightroom

Figure 5.15 shows the image after returning to Lightroom. In this case, the shadows have a bit of detail but the highlights are too bright. I feel that overall my brightness is about right, so I’ll skip the Exposure slider. My first step increases the Shadows to +88 and Highlights down to -40. As you can see in Figure 5.16, this gets the histogram looking good, but the image still feels a little flat. Increasing the Whites +20 and decreasing the Blacks to -30 increases the overall contrast (Figure 5.17). The histogram now shows some clipping in the shadows. As mentioned earlier, a little clipping in the shadows is just fine. Clicking on the Shadow Clipping Triangle circled in red in Figure 5.18 shows a blue overlay to indicate exactly where the shadows have lost detail. As you can see, this small loss of detail occurs in unimportant areas but does add the pure black necessary for a dynamic image. Local contrast is another consideration when processing your images. Setting a deep black and bright white with the Blacks and Whites sliders sets the Overall Contrast. Local contrast is controlled by the Contrast slider and the Clarity slider. The Contrast slider increases or decreases contrast in the midtones of the image. The Clarity slider increases or decreases contrast around tight edges. It is similar to sharpening but not as refined. I typically add +5-+20 points of clarity on most of my images. Too much however, gives your images that crunch look. Figure 5.19 shows the final image after adding +5 Contrast and +16 Clarity to increase the local contrast. I also used the local adjustment brush to lower the contrast in the courtyard. Highlights in an image (especially those at a distance ) should be lower in contrast and saturation than midtones and shadows. This helps keep the sense of reality

 

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Figure 5.15 Unadjusted RAW.dng file in Lightroom’s Develop module

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Figure 5.16 Shadows increased to +88 and Highlights down to -40

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Figure 5.17 Decreasing the Blacks to -30 and the Whites to +20

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Figure 5.18 The Shadow clipping warning turned on

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Figure 5.19 Final image after increasing Contrast to +5 and Clarity to +16

 

Using Photoshop and Lightroom together to blend and process images is a powerful way to capture high dynamic range scenes. The Photoshop portion of the workflow is effortless, and the adjustments back in Lightroom are intuitive. So why then would you need anything else? A couple of answers come to mind. First and foremost, the deghosting function in Lightrooms Photo Merge > HDR does not work as well as I would like.

Figure 5.20 shows a comparison of the image from Figure 5.6. The same series of images were merged in Lightroom and Photomatix. The enlargement on the left showing obvious artifacts was blended using Lightroom. The clean image on the right was blended with Photomatix. In both cases, I had fixed chromatic aberration before merging. The Lightroom merge was the best choice from a series where I had tried Low, Medium, High and None for deghosting.

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Figure 5.20 Photomatix is better at reducing ghosting artifacts.
Lightroom image on the left and Photomatix image on the right.

 

The second reason to use Photomatix is the ability to adjust the tonality of photos in Lightroom before they get Merged. This ability allows for an unprecedented amount of control over the final image. When either of these considerations becomes an issue, I turn to Photomatix.

 

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This post was condensed from Tim’s Upcoming book “HDR Photography-From Snapshots to Great Shots”.
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One thought on “Using Lightroom’s Photo Merge to HDR

Kathy

Great article, Tim. What is your opinion of the idea that Lightroom’s HDR merge gives “better” results using just 2 exposures, one to preserve highlight detail and one to reveal shadow detail?

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