August 14, 2019

Lightroom Previews

Speed up your editing process and save disk space with Lightroom previews?

Last week, I was working with a client and had a nightmare scenario where my hard disk was full. This didn’t seem to make sense. I only keep 2 months of images on my laptop. The rest are saved to an external drive and backed up to the cloud. I’ve also set up my Dropbox account so that files are stored in the cloud until I need them. How could a 1TB hard drive be full? A search over the hard-drive found a file nearly 400GB big. A bit of investigating and I found it contained Lightroom Previews. A little more investigating and it seemed I could delete the file and free up almost half my hard-drive!

This week, we’ll look at what Lightroom Previews are. The benefits of the various types and then tips on how you can get space back on your hard-drive.

What are Lightroom Previews?

Before we look at the types of previews, let’s understand why Lightroom needs them. As I explained a few months ago in the blog Lightroom – Where are my files?, Lightroom is simply a catalogue pointing to the files on your hard drive or external drive. When you look at your pictures in grid view the Lightroom needs to produce a small preview so you can see the contents of the file. When you double click on a file, it will take a few seconds to show a larger version of the file. During this time Lightroom is building a slightly bigger preview. Finally, when you zoom into an image, Lightroom builds an even bigger preview so that you can edit all the way down to pixel level.

What types of Lightroom preview are there?

You can specify on import, the type of preview that will be built initially. You do this in the import module. On the right-hand panel in the File Handling section, click on the Build Previews drop-down box and you will be given a choice of four previews. They are Minimal, Embedded & Sidecar, Standard and 1:1. Let’s look at what each of these previews does and why you might use them.


With this option, Lightroom will bring the files into your computer in the fastest way possible. However, when you come to open the files and view them outside of the grid view, it will take much longer. If I am working on a live news shoot, I do hardly any editing of my images. Any cropping has been done in Photo Mechanic and all I usually need is the application of a preset. Using the minimal preview speeds up my workflow and turns the images around quickly so they are sat on a picture desk as quickly as possible.

Embedded & Sidecar

To best describe this option, it’s worth understanding how your camera works. Assuming you shoot in RAW, the picture you see on the back of your screen is actually a camera-generated JPEG file. The Embedded and Sidecar preview reads the information that is created to display the JPEG on the back of your camera and generates a preview from this file. This method takes slightly longer to import files into Lightroom but displays an initial preview slightly quicker.


This preview method builds a preview that will allow you to view an image in the Develop module using the Fit display in the Navigator section. It will take longer to import your images into Lightroom but will mean that you can inspect your images at a useable size quite quickly.


The final preview will bring in the image to Lightroom with a preview that will mean you could zoom in all the way to 100% and beyond without waiting for any processing. The downside to this is that it will take significantly longer to import the image into Lightroom.

Smart Previews

The eagle-eyed amongst you will have noticed another box in the import module. Below the Build Previews box was another tick box called Build Smart Previews. This can be quite a useful box to tick if your images are on an external drive that you aren’t connected to when you are travelling.

Lightroom will create a preview that you can view on your laptop. It will also allow you to edit the images on the move. When you re-connect to the external drive, any changes will be updated to the original image. It’s also the way that Lightroom Classic and Lightroom Mobile integrate. If you create a collection that is synched to Lightroom Mobile, a Smart Preview is created.

Why do we need to be careful about Lightroom Previews?

You can see that previews are a vital part of the operation of Lightroom. However, there is a downside. This is also the reason why my hard-drive was full. Each of these previews has to create data in a file that allows the previews to be displayed. As you open and view your images in Lightroom the size of the file will grow. You can check the size of the file by going to the folder on your hard-drive where your catalog is stored. If you don’t know where it is, go to Catalog Settings and click on ‘Show’ on the General tab.

After clicking on ‘show’, you will see the various files that make up your Lightroom Catalog. The previews file will end Preview.lrdata and you’ll be able to see the size of the file. If you are unlikely to be regularly viewing all your images in your catalog then you probably don’t need to retain these previews. You can free up space on your hard drive by deleting the file. However, before you press the delete button you will first need to ensure that you quit Lightroom from running on your computer.

Remember if you do free-up disk space by deleting your previews file in the Lightroom catalogue, it will mean future edits will take a few seconds longer as previews are re-built.

If there are any comments or questions, please drop me a mail. You can also sign up for the Edinburgh Photography Workshop monthly newsletter where you’ll get regular updates on interesting things happening in photography and some great tips. Sign up by clicking here.

Book Now