The Lightroom Catalog (Basic Concepts)

My Lightroom Catalog
Actually, Melk Abbey Library, Austria

I’ve just finished my Introduction to Adobe Lightroom Class.    This was the fourth time I have offered the course and I have found two important themes that have been consistent throughout each of the sessions.  

First I am amazed how much I learn each time I prepare the material for the classes. My students always seem to come up with questions that challenge my own understanding of this remarkably capable program, and I am invariably stimulated to come up with refinements of my explanations. Perhaps, at some point, I will get it all right, but then it will be time to move on to something else.

The other persistant issue that seems to come out of every class is the confusion over the functions of the Lightroom Catalog.  This is so essential for the understanding of how Lightroom works that I spend much of my first two hour class discussing the topic, and yet the misunderstandings always seem to linger.  Mostly, it must be my fault, but I think sometimes the students are so excited to get to the “sexy” parts, especially the powerful editing functions, that they blow right past the boring nuts and bolts of how the program actually works.  At the end of this last class I asked everyone to suggest topics that could have benefited from greater emphasis and it all seemed to come down to the care and feeding of the Lightroom Catalog.  It was only after they had manipulated some images, tried to understand where those changes were to be found, and how to translate them to actual flesh and blood image files, that they appreciated the importance of that obscure catalog.

I’ll try to spend more time on the catalog in my next class, but here is another run at a few questions that might help to clarify what the Lightroom catalog is, and perhaps more importantly, what it is not.

Where do Image Files Go When they are Imported to Lightroom

The first problem is the word “Import”.  Import suggests that the image files are physically added to Lightroom and this is never true.  When images are imported, it is only information about the files that is stored in the Lightroom Catalog. Rather than “Import”, a better term might be “Referenced” since the original image file is not moved or altered.  Lightroom’s import process only involves “telling” the program essential pieces of information about the files, such as that the files exist, where they are located, and how they have been edited in the program.  This is easier to understand when Lightroom is importing information about images that are already on the computer, but confusion can occur when the files are being uploaded to the computer from memory cards.  Lightroom provides a convenient mechanism to import file information into the Lightroom Catalog, at the same time that image files are being uploaded to the computer, but it is important to understand the difference between uploading the physical image file and importing the file information to the Catalog.  Careful study of this overly busy flow diagram may be helpful in separating the two processes.

The Database Advantage

Unlike Adobe Bridge, Lightroom is not a file based management system.  Lightroom is a database, that keeps track of information about each image file.  For each image, the program registers only four pieces of information:

1. A set of previews used to display and manipulate the image 
2. A list of all the editing that's has been applied from within Lightroom
3. The Metadata recorded within the file 
4. The physical location of the file in the computer

Contents of Lightroom Catalog Directory

• Catalog Data: [catalog name].lrcat
• Image Previews: [catalog name] Previews.lrdata
• Smart Previews (Lightroom 5 and later): [catalog name] Smart Previews.lrdata

Because Lightroom is a database, which manipulates relatively short text files, it can perform tasks, such as searching and sorting, much more quickly than file based programs, such as  Adobe Bridge.  This becomes more important when dealing with a large or scattered library.   When my own image library exceeded 400,000 pictures, Bridge became impractically cumbersome, and to take advantage of the efficiency of the database model, I finally made the jump to Lightroom. 

I can't resist pointing out that, although Melk Abbey's ancient library contains about 100,000 manuscripts, incunabula  (printed works before 1500), and books, my catalog has over 400k files, of course of slightly less antiquity.


Keep it in Lightroom : A Disadvantage

As an image management program, Lightroom is amazing, but it does have disadvantages.  Because Lightroom manipulates information about the images and not the image files themselves,  it requires more care with the movement of files.  It is important to establish the habit of only moving files from within Lightroom.  In one sense, Lightroom doesn’t “know” where an image file is, it only knows where we have  told it that it is located.  Files that are moved outside of Lightroom will be lost to the program, generating the dreaded "!" flag on the files, and "?" marking their directories. These orphans can be found and re-registered, but, a lot of pain can be avoided by following the “Keep it all in Lightroom” mantra.

 

Found It : Catabane Falls, Now gone

Where is the Lightroom Catalog?

The Lightroom Catalog is stored in a directory that can be located anywhere in the computer, but, by default, is found at:

Windows: \Users\[user name]\Pictures\Lightroom

Mac OS: /Users/[user name]/Pictures/Lightroom

 
If it is in a different location, it can be found in the Catalog Settings of the Lightroom Preferences.

You can have as many catalogs as you wish.  Some photographers keep separate catalogs for work and personal images, but without a compelling reason to compartmentalize your work, a single catalog may be a simpler option.

What Happens when I Edit Images in Lightroom

Image Edited in Lightroom

The essential thing to understand is that all editing in Lightroom is nondestructive.  Repeat after me, “Nondestructive”.   Changes that are made during editing are applied to the preview image in Lightroom, but not to the actual physical images.  

Actual image is not altered on the drive while
Lightroom Adjustments STAY in Lightroom

These changes can be thought of a series of instructions that are saved with the image information in the Lightroom Catalog.  They affect the appearance of the preview image but are not applied to the pixels of an actual image until the
file leaves Lightroom.  Stepping out of Lightroom occurs when editing switches to an external editor, such as Photoshop, or when the image is“Exported” to a physical file format, such as jpg, tif or psd.  This also occurs when images are shared such as in books, web pages or on social media.

Export Dialog, Leaving Lightroom

 

The key point is that all the editing changes you make are simply a set of instructions that don’t get applied until the image ventures from the warm safety of Lightroom into the dark, pixel based, world, and even then the original Raw file stays intact.  That is why there is no “Save” command in Lightroom.

Wall's End, Guilford Vermont, 
Final image with Lightroom Adjustments Exported the file

The Nondestructive Life

I hope this discussions has helped clarify some of the confusion about Lightroom Catalogs.  The more I try to simplify, the more complex it seems to get.  I have not covered many related topics such as how to move, combine, rename, back-up or delete catalogs.  This could be a topic for a future blog, but all of these details are clarified in numerous articles on the web.  

Summing Up

The essential thing to understand is that Lightroom is a database program used to keep track of images on your computer.  

When you edit photos, rate them, add keywords to them, or make other changes, as long as you are in Lightroom, the  changes are stored in the catalog, but the photo files themselves are never touched. 

 
Don’t you wish life was like this.  Try anything you want, take any risk, make disastrous mistakes, and it is ALL “nondestructive”.  When you finally like the results just press “Export”.

Jeffrey Newcomer
partridgebrookreflections.com