Lesson B: HDR – Adobe Photoshop

Lesson B: HDR

Manage Contrast with Multiple Images

“High Dynamic Range” is the term given to an image that contains a larger-than-usual tonal range from dark to light. Some cameras today natively capture very broad ranges without resorting to combining multiple exposures, as we’re going to do here. Some cameras (including smartphones) can combine images to do this too.

In the folder we’re looking at in Bridge, there are three images whose names begin with “HDR.”

  • Highlight one of those images at a time, looking at the Metadata panel to see their exposure data. Note the differences in the Preview panel too.

Each exposure is about two f-stops apart. In the lightest, the sky is blown out, but we can see details in those shadows. The darkest preserves the sky, but the shadows are black. We are going to blend them in two ways: once in ACR, and once using Photoshop’s Merge to HDR Pro. You’ll see that, although Photoshop’s conversion can be superior, we can make an ACR HDR DNG ASAP IMHO. Sorry.

  • Select HDR-1, HDR-2, and HDR-3, then use the shortcut -R/Ctrl-R to open them in ACR.
  • Use the shortcut -A/Ctrl-A to select all three images in the Film Strip panel.
  • Right-click on one of them, then choose Merge to HDR…. There aren’t many options via this route. Luckily ACR can Align Images and Apply Auto Settings to achieve a well-lit result. Both are almost always required.

Deghost compensates for moving objects or shadows by choosing one of the exposures for such an item (like a bird flying through or a bush wiggling in a breeze). The Overlay shows you where deghosting is taking place. Here, the Low setting looks fine.

  • Click Merge…. You’ll be asked where you would like your new DNG file to be saved. The same folder as the originals should be dandy.

But now what? That DNG is now added to the Filmstrip panel so you can apply adjustments to it. At the bottom of the dialog box, you can choose to Open Object (it will say Open Image if you didn’t change the Workflow Options), which opens the image in Photoshop. You might also choose Save Image…, then choose a format and location. This is a great way to make a quick deliverable for someone who can’t open raw files (which is almost everyone). But we have another experiment to run.

  • In ACR, click Done.
  • In Bridge, select the three original HDR DNGs again, but this time choose Tools > Photoshop > Merge to HDR Pro….

Photoshop launches or comes to the fore and performs some preparations before showing you a large dialog box. Though large, the preview is a low-resolution approximation. The final image will be better than what you see here.

As you can see, there are more options here. More than you need, luckily. Most will make a fringed monstrosity, if you’re not careful. I usually restrict myself to a few adjustments. I enable Remove ghosts and Edge Smoothness to lessen edge glow artifacts. I touch nothing in the Tone and Detail section because even small adjustments muddy the image. I do, however, adjust the Curve fairly often to put more light in the shadows, as I’ve done here.

What is Photoshop going to give you? Not a DNG. It will open an image that is in either 8-bit or 16-bit per channel (the latter affording you more latitude for more adjustments) that you can save in any format you prefer. I usually use PDF or TIFF. Use one of these.

  • Choose 16 Bit for Mode, then click OK to see the better, final result, saving the file as a PSD.

If you should ever choose 32 bit, many startling things happen. All the tonal richness will be preserved, such that you really can’t see it all on screen. So the image looks dark. If you disable Complete Toning in Adobe Camera Raw, you can choose how light or dark the image looks, but all the many tones collected from the three original images will still be there. Few of us ever go the 32 Bit route, unless we’re preparing very special HDR images called radiance maps or image-based lights for 3-D work.