Smart Previews are a low resolution, fully editable preview version of your original RAW file.
Actually, they are DNG files, rendered in Lightroom with a size of 2540px on the long edge that are grouped into a .lrdata file next to your Lightroom catalog.
There are several advantages to using Smart Previews:
THEY INCREASE THE PERFORMANCE OF LIGHTROOM
As soon as you detach your RAW files Lightroom will switch to working with the smaller, lighter Smart Previews. Less data to process means it can be processed faster, hence increasing the performance of Lightroom.
Exporting JPEGs from Smart Previews is also a whole lot faster than generating them from RAW files. I’d guess around 5-10x faster.
YOU CAN SPLIT UP THE CATALOG FROM THE RAW FILES
While this is also possible without Smart Previews, with Smart Previews you keep the ability to access and edit the image of detached drives containing RAW files.
THEY SAVE SPACE
Yes, technically creating additional files on top of the already existing RAW files takes up more hard drive space. However, since Smart Previews allow you to detach your RAW files from your catalog without having an effect on the catalogs functionality you can build a Lightroom catalog that sits completely independently from the RAW files and can be fully functional.
For example, in my Lightroom catalog I have over 100,000 photos (that’s 1.2TB of RAW files), this equals 73GB of Smart Previews. Combined with my catalog file + regular preview file my entire Lightroom catalog is smaller than 100GB. I can fit that on my laptop!
THEY CAN ACT AS AN INSTANT BACKUP FOR YOUR IMAGES
Smart Previews are slightly compressed, low resolution DNG files from your RAW files. At around 2500px on the long end they are around 5 Megapixels. While they aren’t intended to be a backup in any form, you could technically extract the DNG files from the .lrdata file that contains the Smart Previews and re-generate your entire Lightroom catalog. It’s not ideal, since you’ve lost a whole lot of resolution, but it’s a nice to know that you’ll be able to still access a version of the original images.
Because you’re likely to split up the catalog from the RAW files when using Smart Previews you’ve add an extra layer of safety in case the drive with the RAW files fails.
50% OFF MY LIGHTROOM PRESET PACKS
You have 2 options:
1 – BUILD SMART PREVIEWS FROM OLD FILES
Select the images you want to build Smart Previews for, then click on:
Library > Previews > Build Smart Previews
2 – BUILD SMART PREVIEWS ON IMPORT (NEW PHOTOS)
In the Import Panel, make sure that on the top right hand side the box that say: Build Smart Previews is selected. Now Lightroom will automatically build the Smart Previews for you each time you import new photos.
There are several ways of checking if your RAW files have a Smart Preview attached.
1 – select the folder you want to check for Smart Previews, then, in the Library Module, press CMD (Ctrl) + F to open to filter panel at the top. Now, select Smart Preview Status on one of the available columns and make sure to turn off any other filters.
Click on ‘Has No Smart Preview‘, select all (CMD/Ctrl + A) and go to Library > Previews > Build Smart Previews. Done.
2 – Select the images you want to check (in Grid View in the Library Module) and see the status on the top right corner, under the histogram.
In the Develop Module you can see if you’re editing the RAW or the Smart Preview by checking the same area, top right, below the histogram. It will either say:
- Original: Original RAW file
- Original + Smart Preview: Original file attached & Smart Preview available
- Smart Preview: Original file not available & you’re editing the Smart Preview