Where do I turn to learn how to process images effectively?

Question

Emphasis here on the word effectively.

As I've been digging through lots of Questions and Answers here, I've found lots of examples of astonishing results of image processing of RAW files like these. I've also seen plenty of discussion about the relative merits of RAW vs. JPEG, particularly vis-a-vis which one rules and which one drools.

I have Darktable, and I've browsed through its documentation, but it doesn't offer a lot. For example, the section on using the color correction module consists entirely of this:

color board

For split toning move the white dot to the desired highlight tint and then select a tint for shadows with the dark spot. For a simple global tint set both spots to the same color.

saturation

Use the saturation slider to correct the global saturation.

This doesn't really tell me anything I couldn't have gathered through 15 seconds of playing with the tool. It also doesn't help me understand how to use the tool to achieve the effects I want. I'd like to learn how to use this program effectively, instead of stupidly twiddling sliders until I get something that's sort of close to what I'm trying to achieve.

Just to clarify, I'm using this module as an example, but I'm not asking (here) specifically about this module. I'm looking for resources that will help me learn how the various modules impact my image, and how to use them to get the end result I want. At least as important, I'd like to learn how to look at my image, that I already know isn't quite right, and recognize how it isn't right, and what tool will allow me to fix it. Everything I've found so far is more or less a glorified tour of the program's UI.

So, to restate the question, where can I go to learn the artistic aspects of using software like this? I don't really need any help navigating the menus and understanding the user interface, but I need loads of help getting the results I see in my head.

Answer 1

When raw conversion applications first started appearing as consumer products that any digital photographer could buy and use, the primary users of such products often had training and experience processing film and printing from that film in the darkroom. Many of the tools offered by photo processing applications are presented in a way that is understandable to someone with darkroom training and experience.

Almost all digital conversion tools seem to assume the user has a basic understanding of photographic processing that goes all the way back to the darkroom. This understanding is based on recognizing how light used to illuminate a scene and the light/filters used in printing and enlarging will affect the resulting photograph. This informs what can be done in the darkroom - or by extension, on the computer. If one understands light in all of the many facets that apply to creating photographs, then one will more intuitively understand what the adjustments in photo processing applications do to adjust for the light that was used to take an image of a scene and to introduce processes that have their origins in chemical darkrooms.

Instead of trying to find resources that explain the principles of lighting and processing a photo using the documentation for the controls of a specific raw processing application, perhaps it would be more helpful to look for more general resources that discuss light and how the way we light a scene and how we then process that light we captured will affect the resulting photograph we create.

At least as important, I'd like to learn how to look at my image, that I already know isn't quite right, and recognize how it isn't right, and what tool will allow me to fix it.

I think for many of us who don't have a strong background in the analog film darkroom, or at least not with color film, the way we learned it was by playing around with the sliders enough until we recognized what they do, and in which direction they work when they are moved a certain direction. The next step is to start seeing some of the same things in the light illuminating scenes and, when possible, altering the light or adjusting our camera's settings before we take the shot.

One way to learn how the camera does some of what it does to produce a jpeg is to use the camera manufacturer's own raw processing software. Most of them will open a raw image by applying the in-camera settings at the time the image was captured. If it's not the default behavior, it's usually at least an option. You can then see what the camera's processing engine selected for things such as white balance, contrast/highlights/shadows/curves/etc.

When you open a raw file with a third party raw conversion application, you're at the mercy of the application's default settings, which can be quite different from your camera's jpeg processing engine. Most of them ignore some or all of the in-camera settings that produced the camera generated JPEG or jpeg preview image attached to the raw file.

For more regarding that, please see:
Why do RAW images look worse than JPEGs in editing programs?
Why is there a loss of quality from camera to computer screen
While shooting in RAW, do you have to post-process it to make the picture look good?
Are paler raw images normal for a newer sensor with higher dynamic range?

Cambridge In Color has a few articles you might find helpful:
CAMERA HISTOGRAMS: TONES & CONTRAST
CAMERA HISTOGRAMS: LUMINOSITY & COLOR
TUTORIALS: WHITE BALANCE
TUTORIALS: PHOTOSHOP LEVELS
TUTORIALS: PHOTOSHOP CURVES
CONVERTING A COLOR PHOTO INTO BLACK & WHITE

They're all grouped on this page:
PHOTO EDITING TUTORIALS

Answer 2

No specific recommendations because you don't seem to have anything specific you're trying to learn. When you do, use The Google Machine to locate specific resources. Places to obtain information include:

• Books
• Video tutorials (YouTube)
• Online courses (Lynda, Coursera)
• Focused Q&A (StackExchange)
• The Google Machine
• Wikipedia

An approach to consider is constructivism (experiential learning), where you fiddle with stuff until it breaks, then figure out how to fix it and avoid breaking it in the future.

Consider starting with basic non-raw image processing. Focus on learning the underlying concepts. Any resource for any program (or no program at all) should be fine, even if you don't use that specific program. Use the resource as a guide to the concepts and techniques.

If you understand how the tools work, you should be able to figure out how to make the adjustments you want. The most important adjustment tool to understand is probably Curves (along with Histogram) because many tools are just interfaces to Curves (such as levels, brightness, and contrast). A thorough understanding of Curves will lead to learning about other topics, such as color, color channels, color mixing, layers, etc. Much of it ties back to Curves in some way. (From a learning, not necessarily implementation, standpoint.)

As for darktable, it has an unusual processing paradigm or is incomplete, likely both. Some tasks are impossible because the necessary tools are missing. I can usually get better results with RawTherapee. Often I'll get close to what I want, then finish in another program, such as GIMP.