Image editing in Lightroom

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 doesn’t mean it is inferior, as these changes have been made without compromising the quality of the image processing. A digital image is made up of nothing more than a series of numbers and during the image editing process those numbers are changed to new numbers. The Lightroom image processing engine ultimately reduces all of its pixel calculations into a single calculation by the most direct route possible to produce a mathematically purer result, in which any image degradation is minimized. Actually, there is quite a lot of juggling going on, including mode changes and image blending, but the essential point is that everything you do will eventually be applied as a single calculation. Another advantage of the Lightroom image processing engine is that you have full access to all of the image controls when working with JPEG, 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, such as the White Balance, Exposure, and Tone Curve controls, to process any imported image. Lightroom does not use layers, but it does recognize and import layered images (providing you switched on the backward compatibility option when saving your PSD files from Photoshop). If you need to do any kind of layering work, it is quite easy to choose the Edit in External Editor command, carry on processing the image in another program, and save the results back to Lightroom in the form of an edited copy version of the original master image.

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, since 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. Since a typical digital camera will only be capable of capturing up to 4,096 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.