12.4 Conversion from RAW

Most digital photographers have only a rather vague idea of what happens during RAW conversion, and in most cases they’d rather not know any more than they do.  That’s fine.  But there are a few things we’d like to very briefly harp on about RAW conversion in the context of  constructing a workflow—in particular, the fact that there are some post-processing operations that may be better to perform before (or during) RAW conversion than after.  We’ve already touched on some of these in previous chapters, but it’s worthwhile spending just a few minutes elaborating on those observations.
    As detailed in chapter 11, Adobe Camera Raw (ACR) provides a number of data sliders that can be used to adjust various image properties prior to RAW conversion.  Most photographers that I know ignore these and wait until the files have been converted from RAW to make any post-processing adjustments.  But it bears repeating that certain image aspects—most notably exposure and noise reduction—can benefit from an adjustment prior to RAW conversion, and that in some cases a fully equivalent post-conversion adjustment isn’t possible.  In the case of my own equipment (remember that much of post-processing is camera-model-dependent), I’ve found that an initial round of sharpening in ACR is not only beneficial, but can bring out a level of detail that I’ve been unable to achieve using only the post-conversion tools in Photoshop proper.  Exposure adjustments are another prime example: as we saw in section 11.3, the amount of detail that can be reclaimed from massively underexposed images, during RAW conversion, is nothing short of amazing.  Reclaiming details in this way from massively underexposed JPG images simply isn’t possible, and this applies also to RAW images that have been converted to JPG with default conversion settings (see figure below).

Fig. 12.4.1: Some adjustments are better made before RAW
conversion than after.  Left: the result of increasing brightness
in a massively underexposed image, during RAW conversion.
Right: the result of adjusting brightness after RAW conversion instead
of during RAW conversion.  The conversion process resulted
in severe information loss due to the underexposure.  Making the
adjustment during RAW conversion is obviously much more effective
than making it after RAW conversion in this case.

    The table below lists the image attributes most commonly requiring adjustment, and enumerates some of the tools available in ACR and Photoshop proper for adjusting those attributes.  As you can see, ACR provides quite a large array of tools for adjusting various image qualities.  Since many of these have the potential (whether strictly in theory or also in practice) to be more sensitive when applied to the RAW file than to the converted file (i.e., due to the fact that the RAW file contains information from the Bayer array prior to interpolation into pixel color values), it’s worth exploring the use of these controls in ACR.

Tone Curve
Fill Light
Unsharp Mask
Smart Sharpen
Color Balance
Channel Mixer
Luminance NR
Color NR
Reduce Noise
Gaussian Blur
Straighten tool
Crop tool
Crop tool
Retouch tool
Spot Healing Brush

Table 12.4.1: Image attributes and the parameters that
affect them, in Adobe Camera Raw (ACR) and Photoshop.

    As a general rule, I apply only conservative adjustments in ACR, and only when an obvious need for adjustment is present; this is primariliy true for color issues, which I prefer to fine-tune in Photoshop proper.  The exceptions to this general rule are sharpening, noise reduction, the reclaiming of blown highlights; I almost always deal with these issues aggressively in ACR and then apply more subtle follow-up processing in Photoshop proper if necessary. 
    One limitation of some versions of ACR is that you can’t select part of the image and apply postprocessing filters to just that portion of the image (I believe this capability is present in the most recent versions of ACR, however).  Another limitation is that some adjustments in ACR (such as sharpening and noise reduction) can only be previewed when zoomed in at 100%.  Also, when working in ACR you’ll typically be working with the full image—i.e., prior to having cropped it or having reduced the resolution (such as for web distribution).  A common workflow strategy is to convert the entire RAW file (without applying any cropping in ACR) and save the resulting image as a PSD file; from here you can then generate alternate versions for, e.g., web distribution, small medium print, large medium print, etc.  In many cases, this is more convenient than re-processing these different versions from scratch (i.e., going back to the RAW file and performing the conversion anew each time).
    It is nonetheless worthwhile in some cases to consider going back to the original RAW file and re-converting it from scratch in ACR, exploring different parameter settings each time to find the optimal setting for each use of an image.  This may seem to be a hassle, but if your computer isn’t too sluggish it’s generally not too difficult to simply double-click the RAW file in your file manager (to bring up ACR), make some quick adjustments to the sliders in ACR, and then press the Enter key to proceed with the conversion and open the converted file in Photoshop proper.  Finding appropriate sharpening and noise reduction settings may require several iterations of this process, since you really need to see how these adjustments affect the converted file in Photoshop before you can be sure you have the right settings.  However, you should be able to get away with going through this whole process only once (albeit via several iterations) and then storing the settings as defaults in ACR, since the ideal sharpening and noise reduction levels will be largely determined by the properites of your particular camera (and the range of ISO values you tend to use in the field).  Once you’ve set these default values in ACR, you shouldn’t need to adjust them very often; an occasional tweak for images that are exceptionally noisy or in need of extra sharpening would be the exception.
    In my own workflow, the only parameters in ACR that I routinely adjust on a per-image basis are the Recovery slider (to fix blown highlights) and a few of the brightness and contrast parameters.  As you develop your own workflow, you may find others that are more frequently useful for you, given your particular preferences and artistic tastes (or the idiosyncrasies of your camera, and particularly the capabilities of its imaging sensor).  And remember that your workflow may change over time, and that for different types of birds you may have a different workflow that you prefer to apply.  This will obviously affect how you go about deciding which adjustments to perform pre-RAW-conversion versus post-conversion.