Multi-RAW Processing

My first and biggest “aha” revelation about digital photography took place the day I discovered multi-RAW processing—processing a single RAW photo file more than once. For me, the ability to process a RAW file multiple times—taking the best of each processing job for the final image—is the most important advantage that digital photography has over film photography.

If you don’t multi-RAW process, you can take photos with immediacy—but you are losing out on a great part of the richness of digital photography.

Let me back up a second to explain what I’m talking about. If you have a DSLR, it can probably be set to save your photos as RAW files, as JPEGs, or as both. RAW files have different file extensions (for example, NEF for Nikon and CR2 or CRW for Canon)—what they have in common is that these files store all the information from the time of exposure.

Essentially, a RAW file is a potentiality rather than a final rendition. Ansel Adams said of his work that a negative was a score, and the print the performance. In much the same way, a RAW file is the score, and what you do with it in the digital darkroom is the performance.

Embedded within the potentiality of the RAW file is a vast exposure range—as much as +4 to 4 f-stops in either direction from the exposure you made. If you do the math, since each f-stop has twice the exposure value of the previous f-stop, this represents a 2^8 or 256 times exposure latitude. So you can use RAW conversion to salvage poorly exposed photos-but more importantly, you can process the different parts of the photo to expose properly for each different part. Multi-RAW processing means that you are not stuck with one overall average exposure, which may be good in some parts and bad in others.

You can also use multi-RAW processing to selectively change white balance, saturation, and so on.

Got you interested? The best news is that multi-RAW processing is really a snap once you get the hang of it. Let me show you how it works using an actual example.

Sample File

I’ve provided a low resolution version of the red car reflections (red-car-reflections.tif) in TIFF format for you to experiment with and follow the example in this article. I chose to provide this file in TIFF format because I needed to lower the size and resolution of the file (I’m not about to let high resolution versions of my RAW negatives out into the world on their own!).

This TIFF file has the same settings and characteristics as the RAW file of the image, and you can use to it to try multi-processing and to follow along with the example in this article.

Note: In order to make sure that the TIFF file will open in ACR, check the “Automatically open all supported TIFFs” option in ACR preferences as shown below.

Photographing the Red Car

I recently spent some time photographing at a classic car show. The cars were polished up to the nines; what interested me most were the reflections in polished chrome, including the red car I’ll use as an example.

Unfortunately, I had an exposure problem, as you can see in the JPEG version of the photo shown in Figure 1. A single RAW conversion in ACR with default settings provides essentially the same results.

If I exposed for the sky (as in Figure 1), the reflections in the grill was definitely too dark. Had I reversed this and exposed for the dark grill area, the sky would have looked washed out. If you have this kind of exposure problem, you should be using multi-RAW processing.

Organizing Your Files

Before you can process your files in the Photoshop Darkroom, you need to organize them on your computer. Programs like Adobe Lightroom can help you do this.

My own workflow starts with using a memory card reader to copy the RAW files from my camera to my computer. I store the files hierarchically in a chronology based on the date shot.

Once I have the RAW files on my computer, I can inspect them using Adobe Bridge, as shown in Figure 2.

A Tour of ACR

Once I’ve had a look at the photos from a session in Adobe Bridge, I’ll pick one or more images to process. To kick off processing, I start by double-clicking on the image in Bridge, which opens the RAW file in Adobe Camera RAW (fondly known to friends as ACR).

Before I show you the actual way I multi-processed this image, let me give you a small tour of the Basic tab of the ACR application—so you can begin to get an idea of the power that this seemingly modest application hides.

To start with, ACR will open with “As Shot” white balance settings and no exposure adjustments, as shown in Figure 3.

The “As Shot” settings mean that ACR imports whatever White Balance settings you had in your camera; if you were set on auto White Balance, you get whatever the color photospectrometer in your camera comes up with when it read the color temperature of the light at the time of the exposure.

To process the photo so it is darker, simply move the Exposure slider to the left (Figure 4).

To lighten the photo, move the Exposure Slider to the right of 0, as shown in Figure 5.

As I’ve mentioned, you can play around with changing color in addition to exposure. There are a number of sliders that have a big impact on image color. The most important one is Temperature.

When you move the Temperature to the left, an image becomes bluer (Figure 6); when this slider is moved to the right, things change to the yellow end of the spectrum (Figure 7). The Tint slider plays much the same role, but along the magenta-green axis rather than the blue-yellow axis.

Converting Your Image in ACR

To get started with an actual multi-RAW conversion, it helps to plan your strategy in advance. With the photo of the red car reflections, this is pretty straightforward.

This multi-RAW conversion scenario involves combining three individual RAW conversions of the same image:

• First, I’ll process the image for the sky on the right.
• Then, I’ll process a lighter version for the dark grill on the left.
• Finally, I’ll process an even lighter version to bring out dark shadow areas.

Processing the same image three times is actually a pretty common multi-RAW conversion scenario, but other approaches are possible. I’ve had multi-RAW conversions that involve seven or eight different exposure values. When multi-RAW processing is combined with Hand HDR (the subject of my next article), things can get really complex.

Keep in mind that it sometimes makes sense to start by producing an extremely dark version from the RAW file. This works when you are photographing a subject against black. Then subsequent lighter versions are placed on top of the dark versions as layers in Photoshop.

With our red car reflections, the first step is to find good ACR settings for the right-hand side of the image.

With the image opened in ACR, if you know the light conditions used to shoot the image, you can usually get a pretty good starting place for White Balance by selecting from the White Balance drop-down list, shown in Figure 8.

Typically, I also boost the Saturation and Vibrance a bit (see the settings in Figure 9). When I’m happy with my settings, I save them as a separate XMP file using the menu shown in Figure 9. This menu is opened by clicking the tiny triangle at the right of the Basic bar. The point is that with many conversions from the RAW, you may want to be able to find your way to back to your original settings.

Since the only work has been on the Basic tab of the ACR dialog, it is only necessary to save the Basic settings, as shown in Figure 10. The example only shows working with settings on the ACR Basic tab.

I do like to save my ACR settings files—which are XML files with an XMP file suffix—where I can find them, namely in the working folder I am using to save my photo conversion work in progress as shown in Figure 11.

With your settings selected and saved, the next step is to open the RAW conversion in Photoshop. Be sure to open a copy, not the original. If you hold down the Alt key, the Open Object button in ACR changes to read Open Copy—so make sure you hold down the Alt key before you open your conversion.

The impact of opening a copy is to make sure your ACR settings are not applied to the photo metadata. This makes it easier to open subsequent conversions from the “As Shot” settings.

Working in Photoshop

The first thing you should do when your RAW conversion opens in Photoshop is to save it as native PSD file. Choosing “Save As” rather than “Save” from the File menu is a good habit to have.

You now have a single image with one layer (the Background) open in Photoshop (Figure 12). Clearly, the left side is too dark.

With the image happily open in Photoshop, go back to Adobe Bridge. Double click the image once again to open it again in Adobe Camera RAW.

With the image open for the second time in ACR, choose Previous Conversion from the drop-down menu shown in Figure 13 to start work on a second conversion starting with the settings of the first conversion.

From the starting place of the first conversion, in ACR move the Exposure Slider to the right to create a lighter version (Figure 14).

Once again, make sure to hold down the Alt key to open a copy before opening this RAW conversion in Photoshop.

You now have the saved and converted background in Photoshop, and a new lighter version as well. Next, the rubber starts to meet the road when you combine the two versions.

Choose the Move Tool from the Photoshop Toolbar (located on top of the toolbar).

With the Shift key held down, use the Move Tool to drag the lighter version on top of your saved background. Holding down the Shift key constrains the move operation so that they two layers are exactly aligned. This layer constraint is crucial to the success of the multi-RAW process. Don’t release the shift key until after you have released the mouse button.

Your photo will now have two layers, with the lighter version on top, as you can see in Figure 15.

It’s a good habit at this point to name the new layer by clicking on it and choosing Layer Properties from the drop-down menu. I confess, I don’t always take the time to name my layers—and boy do I regret it when I have to come back to the Layer stack after some time has elapsed and I try to figure out what does what.

Combining the Layers with a Gradient

The next step is to combine the two layers so you can only see a portion of the lighter layer on the left and a portion of the darker layer on the right in the image window. To do this, use a layer mask and gradient.

To combine the two layers, with the Lighter layer selected in the Layers Palette, from the Layer menu, choose Layer Mask > Hide All, as shown in Figure 16.

It can be hard to remember what Layer masks do, so think of it this way. In relation to the layer the mask is attached to, a black Layer Mask conceals and a white Layer Mask reveals.

As you can see in the Layers palette shown in Figure 17, the Hide All Layer Mask appear as a black thumbnail associated with the Lighter layer. You can see the original conversion with the lighter conversion on top as a masked layer.

Next, find the Gradient Tool (it is located about half way down the Photoshop Toolbar, and may be hidden behind the Paintbucket Tool).

With the Layer mask selected on the Lighter layer, click and drag the Gradient tool from left (white) to right (black) in the image window. A gradient blend seamlessly combines the lighter and darker versions. It’s clear if you look at the image file shown in Figure 18 that the Gradient blend combines both lighter and darker versions, and is a big improvement over either individual RAW conversion.

Once you get the hang of it, adding a layer mask and drawing a gradient is a very quick process.

You can get a better idea of what is going on by looking at the Layer Mask in thumbnail (Figure 18), or by looking at the mask itself in a larger size (Figure 19). By looking at the Layer Mask itself, you can see how the layers will blend.

If you are curious as to how to you look at the Layer Mask, the answer is to make it visible by itself in the Channels Palette (Figure 20). The Layer Mask is the only channel that is set to be visible in the Channels Palette.

A layer mask is also a channel (if this sounds confusing, don’t worry too much about it).

Painting in Light Areas

The next step in my plan for this image called for lightening a few selective areas even further. So, it’s back to Adobe Bridge to open ACR with the RAW file once more. Once again, double-click the image in Bridge to open a new copy in Adobe Camera RAW (my kids would say, “Not again!”).

With the image open a third time in ACR, choose Previous Conversion from the drop-down menu (shown in Figure 13) to start work on a third conversion, beginning from the settings of the second conversion.

Make this version even lighter by sliding the Exposure Slider further to the left. Open a copy, making sure to hold the Alt key down.

With the lightest version open in Photoshop, again use the Move Tool constrained with the Shift key to place the lightest version on top of my layer stack (Figure 21). The Lightest layer is positioned with a mask on top of the Layer stack.

Next, by selecting Layer > Layer Mask > Hide All add a Hide All Layer Mask to the new (lightest) layer.

To “paint” in the areas of the lightest layer, make sure the layer mask attached to the Lightest layer is selected. Then choose the Brush Tool from the Toolbar.

Use the Brush Tool on the layer mask to paint in selective opacity. You should select White as the color for the Paintbrush. The Paintbrush should be set to 0% hardness, and have only partial opacity (about 35% is a good starting place). I like to use a partially opaque Brush for more control.

The white areas in the Layer Mask shown in Figure 23 are where I’ve painted some transparency—and where the lightest layer partially shows through.

Conclusion

At this point, I like to archive a copy of my image with the layer stack intact. Then, I merge down the layers and proceed to other work in the Photoshop Darkroom, processing the image further (but that’s another article for another day).

If you look at the combination of the three layers in this simple multi-RAW post-processing (Figure 24), you’ll see that it is a vast improvement over where the image started (Figure 1). The finished multi-RAW processed image (Figure 24) is appropriately exposed in all areas.

It’s worth taking the time to get up to speed with multi-RAW processing. Multiple processing of a single RAW file should revolutionize the way you think about making digital exposures. Many photos are possible with multi-RAW that you simply couldn’t do any other way. Unlike HDR imaging, there is no requirement that you take multiple bracketed exposures—so from a shooting perspective, it is really simple to implement multi-RAW, because you don’t have to change anything you do until you get your photos home to the computer.

Other Photoshop Tutorials

Creativity in the Photoshop Darkroom by Harold Davis: Multi-RAW Processing | Creating HDR Images by Hand [Part I] | Creating HDR Images by Hand [Part II] | Converting to Black and White

Advanced Photoshop Tutorials by Jay Kinghorn: Layer Masks | Smart Objects | Advanced Masking | Image Sharpening | Burning and Dodging

More

• Harold’s member page
• Harold’s gallery page

Harold Davis is a photographer and author. His photographs have been widely published, exhibited, and collected. Many of his fine art photography posters are well known. Harold’s images have won a Silver Award in the International Aperture Awards 2008 competition, and inclusion in the 2009 North American Nature Photography Association Expressions Showcase.

Harold is the author of The Photoshop Darkroom: Creative Digital Post-Processing (Focal), Creative Composition: Digital Photography Tips & Techniques (Wiley), Creative Night: Digital Photography Tips & Techniques (Wiley), Creative Close-Ups: Digital Photography Tips & Techniques (Wiley), Practical Artistry: Light & Exposure for Digital Photographers (O’Reilly Digital Media) and other books. Harold gives frequent digital photography workshops, many under the auspices of the Point Reyes National Seashore Association.

Text ©2009 Harold Davis.