The Complete Guide To Lightroom Classic Previews

by Andrew S. Gibson
The Complete Guide To Lightroom Classic Previews

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Do you know how many types of Preview there are in Lightroom Classic? The answer is six – and they’re all used at various stages of the Lightroom Classic workflow to enable you to see what your photos look like.

Why does Lightroom Classic use Previews?

Lightroom Classic is a Preview based application – no matter which module you’re using, you’re always viewing Previews of photos rather than the photos themselves. But why is that?

The answer is that Lightroom Classic uses parametric image editing (or developing in Lightroom Classic language). This is where the application creates instructions for editing an image, rather than adjusting the photo’s pixels. Lightroom Classic saves the instructions in its database (the Catalog) in the form of text commands that look something like this:

Blacks2012 = 0,
BlueHue = 0,
BlueSaturation = 0,
CameraProfile = “Adobe Standard”,
Clarity2012 = 0,
Contrast2012 = 67,
ConvertToGrayscale = false,
EnableCalibration = true,
EnableColorAdjustments = true,
EnableEffects = true,
EnableSplitToning = true,
GreenHue = 0,
GreenSaturation = 0,
Highlights2012 = -49,

Lightroom Classic applies those text commands to your photo and then builds a Preview that shows you what your photo looks like with those changes. The Preview is updated in real time as you use Lightroom Classic.

Learn more: What Is The Lightroom Classic Catalog?

Types of Lightroom Classic Preview

It’s important to understand the differences between the six types of Lightroom Classic Preview as the way you use them (by telling Lightroom Classic which ones to build) makes a big difference to Lightroom Classic’s speed and efficiency. You need to build the right Previews if you want Lightroom Classic to run at optimal speed. Let’s see how to do that.

Building Previews during import

You can select which types of Preview you want Lightroom to build when you import your photos into Lightroom Classic. You can also build Standard, 1:1 and Smart Previews at any time in the Library module.

The important thing to bear in mind that all of these Previews (with one exception) are used in the Library module (and by extension the Book, Print, Web modules etc.) but not the Develop module, which uses its own type of Preview.

The one exception is Smart Previews, which are used by both the Library and Develop modules under certain conditions.

Learn more: The Ultimate Guide To Using Smart Previews In Lightroom Classic

These are the Previews you can build during import.

1. Minimal Previews

These are the smallest Previews possible. Minimal Previews save space and time but aren’t much good for viewing photos as they are so small. The only reason for using Minimal Previews is because you want to import your photos as quickly as possible.

Lightroom Previews

2. Embedded & Sidecar Previews (Lightroom Classic only)

This option tells Lightroom Classic to use the JPEG Preview built into the Raw file, if it exists. It uses the same Preview technology used by applications like Photo Mechanic and is only available in Lightroom Classic.

Lightroom Previews

Choose this option if you want the fastest import possible that gives you a Preview that’s good enough to view in the Library module.

Learn more: How to Import Photos Faster Into Lightroom Classic

3. Standard Previews

Standard Previews let you view photos in Loupe View, but are not large enough for you to zoom in to examine fine details or focusing accuracy.

Lightroom Previews

It takes longer to build Standard Previews, but they are more accurate than Minimal or Embedded & Sidecar Previews.

You can set the size of standard Previews in the Catalog Settings. The best option to pick is Auto as it tells Lightroom Classic to build Previews that match your monitor’s resolution.

Note: Neither Minimal or Embedded & Sidecar Previews are as accurate as Standard Previews. If you select either option during import Lightroom Classic automatically builds Standard Previews afterwards. This can slow Lightroom Classic down, so for that reason you should only select Minimal or Embedded & Sidecar Previews when you need to import your photos quickly.

4. 1:1 Previews

The best quality Previews of all are 1:1, but they takes longest to build. This are full-size Previews that let you zoom into your photos at 100% when looking at them in Loupe view. With 1:1 Previews there is no delay when you zoom into a photo.

Lightroom Previews

1:1 Previews are larger than Standard Previews and take up a lot of hard drive space. Lightroom Classic handles that by discarding 1:1 Previews after a set amount of time. The default is 30 days, but you can change that in the Catalog settings if you need to.

Lightroom Previews

5. Smart Previews

Adobe introduced Smart Previews in Lightroom 5. A Smart Preview is a high-quality, highly compressed Preview that measures 2540 pixels along the longest edge.

Smart Previews enable photographers to view and develop photos without access to the original photo files. You can also use them to synchronize with Adobe Creative Cloud apps and services such as Lightroom for mobile, Lightroom web and Adobe Portfolio.

Earlier I said that Smart Previews are both highly compressed and high-quality. This sounds like a contradiction but it’s true – you can’t tell a Smart Preview apart from a full-size Preview in terms of image quality. The only difference is that a Smart Preview is smaller.

Note: You can build Standard, 1:1, or Smart Previews at any time in the Library module by selecting the images and going to Library > Previews and selecting the Preview type required. The option to build Minimal or Embedded & Sidecar Previews only appears in the Import window.

6. Develop module Previews

When you switch from the Library module to the Develop module the Preview Lightroom Classic uses to display your photos changes. Lightroom Classic renders high-quality Previews that let you see the result of actions like adding sharpening, applying noise reduction, and retouching images.

These Previews are cached rather than saved in a Preview file, otherwise, they would rapidly eat up most of your hard drive space.

Creating 1:1 Previews in the Library module makes no difference to the speed at which Lightroom Classic renders Previews in the Develop module. But if a Smart Preview exists for the photo Lightroom Classic uses the Smart Preview instead of rendering a Develop module Preview under one of two conditions.

a. The hard drive containing the original photo file is disconnected from the computer.

b. You have Lightroom Classic or Lightroom 6.7 or later, the hard drive containing the original photo file is connected to the computer, and you have the Use Smart Previews instead of Original for image editing preference enabled in Preferences (see below).

Lightroom Previews

Note that if you zoom into 1:1 Lightroom Classic stops using the Smart Preview and renders a full-size Preview instead.

As Smart Previews are smaller than full-size Previews they enable Lightroom’s Develop module to run much faster.

The simple approach to Lightroom Classic Previews

Lightroom Classic Previews are somewhat confusing, especially for beginners. This is hardly surprising considering there are six types! So let’s keep things simple. These are my recommended Previews to use.

  • When you import images into Lightroom Classic, choose either Standard or 1:1 Previews. If you intend to zoom into your images while viewing them in Loupe view, you definitely want to pick 1:1 Previews. Otherwise, pick Standard.
  • If you want to view the images in Lightroom for mobile or Lightroom web then tick the Build Smart Previews box. Do the same if you intend to use Smart Previews in the Develop module.

Introducing Lightroom Classic ebookThanks for reading. You can get more great articles and tips about Lightroom Classic and photography in my popular Mastering Photography email newsletter. Join today and I’ll send you my ebook Introducing Lightroom Classic and 47 PhotoTips cards. Over 30,000 photographers subscribe. Enter your email now and join us.

Mastering Lightroom Classic: Book Two – The Develop Module ebook
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More great Lightroom Classic tips, tricks and tutorials!


George Mitchell August 18, 2018 - 7:53 am

I have always look to Andrew to help or assist with problems relating to Lightroom and sound advice is always ready. Cannot speak too highly of the help I have received in the past.

Andrew S. Gibson August 18, 2018 - 10:16 am

Thanks George, always happy to help!

Anthony August 28, 2018 - 4:24 am

Andrew, your articles are much appreciated. However, I run LN 5 and not V6, so please be specific as to which version you are referencing in your postings.

Andrew S. Gibson August 28, 2018 - 11:25 am

Hi Anthony, the articles reference Lightroom Classic CC, with guides given where needed for people who use older versions of Lightroom.

terry connelly March 11, 2020 - 7:23 pm

I have created a new catalog as my current one has gotten very large and is slow. I cannot find anything that tells me how I can get the old previews and information from the old catalog into the new one.

Andrew S. Gibson March 12, 2020 - 7:29 am

Hi Terry, how large is large? If you’re using Lightroom Classic it can handle Catalogs with a million plus photos in it without problems. If I were you I’d open the old Catalog and go to File > Optimize Catalog. When you do this Lightroom analyzes the Catalog and optimizes it for speed. If you really feel you need to start over, then again, open the old Catalog, select all the photos (you can do that in the All Photographs Collection in the Collections panel) and go to File > Export as Catalog. Lightroom will make a new Catalog with all your photos in it for you.

terry connelly March 12, 2020 - 3:23 pm

Thank you so much for getting back to me on my question. I did go ahead and create a new catalog. As I had not seen your response yet I went ahead and imported the photos. The new catalog was actually slower than the one I imported from. I am not sure how that makes sense, but I went ahead and put the folder which had 130479 photos in it back where it was initially.

I have optimized, synchronized, made the previews smaller and done everything else I have read online to do to speed things up. Once the photos get back to where they belong I will check in with you again and let you know where I stand.

Thank you so much for your help

Andrew S. Gibson March 12, 2020 - 7:22 pm

Don’t forget to check your hard drive space either. If there’s less than 15% free that will slow your computer down as well.


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