A definitive guide to working with the image-processing controls in the Develop module
One of the most powerful features in Lightroom is the image-processing engine, especially the way the image-adjustment processing is deferred until the time you choose to edit in Photoshop or export an image. This method of image processing actually originated in the early days of computer imaging, when deferred processing was adopted by programs such as Live Picture and xRes as a means to speed up the image editing. Computers were a lot slower back then, but it was possible to manipulate large image files in real time on relatively slow computers (with as little as 24 MB of RAM) and defer the image-rendering process to the end of a photo edit session.
Of course, these days, you can edit large images in no time at all in Photoshop. But one of the key advantages of Lightroom is that you can apply a crop, spot the image, make localized adjustments, tweak the color, do some more retouching, readjust the crop again, and so on, without ever touching the pixels in the original photograph. In a conventional pixel-editing workflow, the pixels are always modified in a consecutive sequence of steps. When you work in Lightroom, no restrictions are placed on the order in which you do things, and the edit changes you make in the Develop module are applied only when you output a photo as a rendered file, such as a PSD, TIFF, or JPEG.
Smarter image processing
The Lightroom image-processing engine is notable for a number of reasons. First, the Adobe engineers have made Lightroom simple to use—there are no color management settings, color space issues, or profile warnings to worry about. But just because the image processing is simpler does not mean it is inferior, as these changes have been made without compromising on quality. The Lightroom image-processing engine ultimately reduces all of its pixel calculations into a single calculation, in which any image degradation is minimized. Another advantage of the Lightroom image-processing engine is that you have full access to all of the image controls when working with JPEG, PNG, TIFF, and PSD images, just as you have when working with raw camera files. You can use any of the image controls available in the Lightroom Develop module.
Lightroom uses a single RGB workspace to carry out all its image calculations, which is similar to the ProPhoto RGB space that was originally specified by Kodak. It uses the same coordinates as ProPhoto RGB but has a gamma of 1.0 instead of 1.8. By using a 1.0 gamma, the Lightroom RGB workspace is able to match the native 1.0 gamma of raw camera files, and its wide gamut can therefore contain all the colors that any of today’s digital cameras are capable of capturing. For these reasons, the Lightroom RGB workspace is ideally tailored to the task of processing the color data contained in the raw camera files. Concerns about banding in wide-gamut color spaces have perhaps been a little overrated, because it is really quite difficult to pull apart an image in ProPhoto RGB to the point where you see gaps appearing between the levels. Suffice it to say, the Lightroom RGB space uses a native bit depth of 16 bits per channel, which means that Lightroom is able to process up to 32,768 levels of tonal information per color channel. Because a typical digital camera will only be capable of capturing up to 4096 levels per color channel, it is probably true to say that the Lightroom RGB workspace can safely handle all of the tone and color information captured by any digital camera.
The Develop controls in Lightroom can be accessed as soon as a low-resolution preview has had a chance to load, instead of waiting for a full preview. For example, if a Smart Preview is available, Lightroom loads this first, before loading the full-sized image. When going to the Develop module, individual panels are not loaded into memory unless they are already open. This helps improve the initial first launch speed of the Develop module. In Lightroom Classic CC, there is now faster switching from the Library to Develop modules. Furthermore, if you have 16 GB RAM or more, sequential navigation (using the keyboard arrows to move from one photo to the next) in Develop is faster in Lightroom Classic CC. This is because Lightroom now pre-caches upcoming photos, both before or after the direction you are navigating in. While you spend a few seconds on an image, Lightroom pre-loads the next two or three images to enable faster scrolling through these.