I don’t mean to mystify things, but this hasn’t been discussed frequently.
Double processing a single Raw file is a great post-processing technique for a few reasons:
- Solve the problem of moving objects in digital blending.
- A way of recovering details in highlights and shadows with less worry about clipping.
- A more efficient way to maximize the dynamic range captured in your image.
I often use double processing technique for blending images with moving objects.
The question is: Should you be using it all the time? When should you NOT use it?
Image selection is the KEY to successful double processing a single RAW file.
Before we dive into the details, let’s go through how you can do double processing in Photoshop.
Or maybe jump straight to the secret?
Double Processing A Single Raw Image
If you’re new to double processing, it’s a post-processing technique where you pick a single RAW image, duplicate it, optimize one for the highlights and one for the shadows, and blend both together.
- You don’t have to worry about how the Highlights or Shadows slider bar affect each other
- Because you are processing a single file, you don’t need to worry about ghosting caused by movement!
The one thing that you need to remember is that this technique works best with Raw files. You can use JPEG but you won’t be able to recover as many details from the highlights or shadows.
Doesn’t make sense? Carry on reading 🙂
Carry on reading 🙂
Let’s say you’ve taken 3 bracketed images like below and you want to digitally blend them together.
You’ve tried blending all methods that you know.
But you still notice ghosting from the movement in the trees on the top right-hand corner of your image.
You have spent hours trying to solve this problem. You’re frustrated and giving up…
You don’t have to give up on your image.
Here’s the solution:
Take the middle exposure (0EV) for double processing (0EV works most of the time)
If you use Lightroom, cmd (Mac) or ctrl (Win) +E to open the image in Photoshop. Otherwise, you can also open it straight up in Photoshop.
Preparing For Double Processing
Before we begin, you need to prepare your image. We’ll be using Adobe Photoshop CC which has a built-in Camera Raw Filter.
If you open your image in Photoshop from Lightroom:
- Double click to convert it to a layer.
- Right-click on the layer and choose Convert to Smart Object. You should see a little icon appearing on the lower right-hand corner of the thumbnail telling you it’s now a smart object.
- Now duplicate this layer so you have 2 exact copies (both are smart object – this is important!).
- You’re going to optimize for shadows first in the example. Select the bottom layer and go to Filter > Camera Raw Filter.
- Optimizing for shadows means recovering the details from the shadows. Use the Shadows slider bar to brighten up the shadows until you see details. Don’t over do it though 🙂 You can also tweak with the Blacks slider bar to get the best results. Focus on the shadows and don’t worry about the blown out highlights. Click OK when you’re done.
- Now select the top layer in the layers panel to optimize the highlights. Again, go to Filter > Camera Raw Filter and use the Highlights slider bars to recover details in the highlights and the Whites slider bar to tweak if needed. Focus on the highlights and ignore the shadows. Click OK when you’re done.
- You have both layers optimized and ready to blend!
If you open the image directly using Photoshop, you will go through Adobe Camera Raw (ACR) first:
- You can either optimize for the highlights or shadows first, it doesn’t really matter. In this example, we will optimize for the shadows first just to keep things consistent.
- Similar to Step (5) above, you optimize for shadows by using the Shadows slider bar to brighten up the shadows.
- Once you’re done, hold down the Shift key and you should see “open image” becomes “open object”. Click to open your file as a smart object.
- In the Layers panel, duplicate the layer so now you have 2 exact copies. The duplicated layer is also a smart object and has the ACR settings from before. All you need to do is double click on the Camera Raw Filter in the Layers panel, reset the settings from before and optimize for the highlights using the Highlights slider bar and tweak with the Whites slider bar if necessary.
- Now you’re ready to blend!
If you have an older version of Photoshop and doesn’t have Camera Raw Filer in the menu:
- Before you open your image in Photoshop, make a copy first.
- Open one of the copies in Photoshop. Because it’s a Raw file, ACR will pop-up first. Optimize for shadows and open it as object like in Step (3) above.
- Now open the other copy of the Raw file, optimize for the highlights this time in ACR and open it as an object.
- Because both files are opened separately, you have to move one file to another to make them as layers in a single file. You can do this by either copy and paste, or use the move tool to drag one file to another.
- Job done and you’re ready to blend!
There are many ways of blending (free hand, blend if, luminosity masks, color range, custom mask, etc). We won’t go into the details because each method can be a long post!
I used free hand blending in this example because I want to blend in the darker sky (top layer) and it’s a rather small area on the image. I’ve tried blend if but it didn’t work very well and I didn’t want to spend too much time with luminosity masks.
I can almost hear the drum roll 🙂
If you zoom into the shadows, you can see IMAGE NOISE – our number one enemy, apart from blur, chromatic aberrations and all others that are bad for photos.
You wonder how did this happen?
Let’s take a look at the histogram of the Raw image (0EV).
The shadows are touching the far left of the histogram and are almost clipped. Bear in mind that this is 0EV.
Would it make any difference if we use +2EV for double processing?
Let’s take a look at the image and the histogram.
Slightly better, although you still can see some image noise but not as severe as 0EV. The histogram shows there is still a lot of shadows in the far left.
Brightening shadows will introduce noise. No matter how careful you are.
Why? Because of the low signal-to-noise ratio.
It’s technical and the concept can be difficult to understand.
But what you should take away from this is that you need to be careful when choosing an image for double processing.
Always check the histogram for all the images and pick one that has a more “central distribution”, meaning the graphs are more towards the center instead of to the far left or the far right.
Double processing a Raw file is a post-processing technique to help you recover details, maximize the dynamic range and solves the problem of moving objects in blending.
Always check the histogram of your image before selecting a file for double processing to minimize image noise in the shadows.
- The ultimate guide to exposure blending
- Multiple RAW processing in Photoshop
- Digital camera image noise
- CCD signal-to-noise ratio