Читать книгу Adobe Photoshop Lightroom Classic For Dummies - Rob Sylvan - Страница 34

Before I get into what the controls do, I’d like to talk about what previews are and what they do. I was once asked a great question by a new user who was trying to understand how previews work: “If my photos are never altered and never in Lightroom Classic, then what am I looking at when I’m working?” What a great question! The answer, of course, is preview files. You encounter two types of regular preview files in all modules except Develop (Develop needs to access the actual photos for its on-the-fly preview when you edit, so it doesn’t use these previews):

 Standard: These are what you see in all the modules except Develop. The size and quality of these previews are determined by the settings you choose on the File Handling tab.

 1:1: These previews match the pixel dimensions of your source files. These are used when you view images at 1:1 view in the Library.

Therefore, you’re almost always looking at a cached preview of your photos. While you make adjustments in Develop, Lightroom Classic re-renders previews on the fly to show you the effect of the adjustments (but never applies changes to the original photos). All these previews are stored in the Preview cache alongside the catalog file. Because Lightroom Classic renders the previews as needed, they’re not essential files and are not included in the backup process. However, because they’re rendered for every photo you import, they can require a significant chunk of disk space over time. This brings the discussion back to the File Handling tab of the Catalog Settings dialog (refer to Figure 2-7).

You can tweak your Preview Cache settings in three ways:

 Standard Preview Size: Use this drop-down menu to choose a pixel size that best matches the resolution of your monitor, or let Lightroom Classic do it for you and just leave it set to the default of Auto. Lightroom Classic uses standard-sized previews when you view the image at Fit Screen, meaning you see the entire image on-screen. Because of this, you don’t need to generate a standard-sized preview that is greater than the resolution of your monitor.

 Preview Quality: This drop-down menu allows you to determine the amount of JPG compression applied to the standard-sized previews. The default setting of Medium is a good compromise between quality and file size.

 Automatically Discard 1:1 Previews: Use this drop-down menu to configure how long Classic keeps the 1:1 previews in the cache. Because they’re high-quality, pixel-for-pixel copies of your source files, such preview files can be quite large, so you might not want them lying about on your hard drive for too long. Lightroom Classic, of course, re-renders them if they’re needed after having been discarded, but then you have to wait for the render to complete. Leaving the setting to After One Week is a good balance between performance and keeping a damper on the growing size of the cache.

You can force Lightroom Classic to delete 1:1 previews at any time by going to Library ⇒ Previews ⇒ Discard 1:1 Previews. Therefore, you’re not entirely dependent upon that setting if you find your Preview cache is taking over your hard drive.