When you want to produce an HDR image in Photoshop CC, you usually shoot a series of exposures. Alternatively, and usually with quite good results, you can change the exposure after the fact using Camera Raw. (You’ll want to use a Raw image, not a JPEG image, for this technique.) Here's how:

  1. Shoot the best exposure possible.

  2. Transfer the image to your computer.

  3. Open the image into Camera Raw.

    Make sure that Camera Raw’s Workflow Options — click the blue line of info below the preview — are set to 16-bit color.

  4. Adjust the image until it looks perfect.

  5. Click the Open Image button to open from Camera Raw into Photoshop.

  6. Copy the image into a new file and save in the TIFF format.

    Choose Select→All, then choose Edit→Copy, followed by File→Close (don’t save), and then File→New. (The preset will be Clipboard, so just set Background Contents to Transparent and click OK.) Choose Edit→Paste followed by File→Save As, choose TIFF as the file format, and save. Using this procedure strips out the EXIF data, making sure that Merge to HDR Pro doesn’t use the wrong exposure value.

  7. Reopen the original Raw file into Camera Raw.

  8. Drag the Exposure slider to the left to reduce the exposure by 2.

    Two is just a general guideline — watch for maximum detail in the highlights.

  9. Hold down the Option/Alt key and click Open Copy.

    This prevents Camera Raw from overwriting the earlier adjustment in the file’s metadata.

  10. Copy the image into a new file and save in the TIFF format. (Repeat Step 6, using a sequence number or other change to the filename to differentiate from the first TIFF.)

  11. Reopen the Raw file into Camera Raw a third time.

  12. Drag the Exposure slider to the right to increase the exposure by 2.

    Again, two is just a starting point — you want to see maximum detail in the shadows.

  13. Hold down the Option/Alt button and click Open Copy.

  14. Copy the image into a new file and save in the TIFF format. (Repeat Step 6, using a third filename.)

You can now use these three adjusted images in Merge to HDR Pro, as described in the following section. The results likely won’t be as great as using a series of separate exposures, but should be better than a single exposure.