If you’ve ever wondered how you can make Lightroom faster in the Develop module then converting your Raw files to DNG may be part of the answer.
To understand why, first we need to understand that Lightroom uses a different type of preview in the Develop module than it does in the Library module.
Here’s how it works.
Previews in the Lightroom Library module
When you import your images into Lightroom you’re given the choice of building either Minimal, Embedded & Sidecar, Standard or 1:1 previews. These are used by the Library module, but not the Develop module, to display previews of the photos in your Catalog.
Note: I recommend you select Standard if you don’t want to zoom into your photos in the Library module, or 1:1 if you do. 1:1 previews take longer to build as they are larger and contain more data.
Above: Lightroom uses Minimal, Embedded & Sidecar, Standard or 1:1 previews to display photos in the Library module.
Previews in the Lightroom Develop module
Lightroom builds a different preview in the Develop module based on the current state of your Raw file, taking into account the developing you have carried out on it. The preview is updated every time you do something new to the photo.
Above: Lightroom builds previews in the Develop module as they are needed. Using DNG means Lightroom can build previews faster, saving you time.
This is where converting your Raw files to DNG comes in. DNG (short for digital negative) is an open source Raw file format created by Adobe.
When you convert a file to DNG in Lightroom it adds something called Fast Load Data to the file. This is a partially processed preview that lets Lightroom render previews faster in the Develop module.
The speed savings are impressive. Adobe says a DNG file with fast load data will load up to eight times faster than one without it. The more cores your computer’s processor has, the greater the gains, as each core can build a different part of the preview at the same time. This isn’t possible with other Raw files.
Another benefit is that DNG files are smaller than other Raw formats, and take up to 20% less hard drive space. High volume shooters will appreciate this.
Converting files to DNG in Lightroom
The easiest way to convert your Raw files to DNG is to do it when you import them into Lightroom.
Make sure you go to the File Handling tab in Preferences and tick the Embed Fast Load Data box (below), otherwise you will miss out on the speed increase that DNG gives you.
You should also import your files from the camera’s memory card rather than copy them to an external hard drive before the import.
These are the key steps to follow during the import.
Select Copy as DNG in the Import window. This tells Lightroom to copy the Raw files from the memory card to the specified folder on your hard drive and convert them to DNG.
Set Build Previews to 1:1 or Standard in the File Handling panel.
After the import, go to the Catalog panel, select Previous Import, select all the photos in the Collection and go to Library > Validate DNG files. Lightroom checks the new DNG files to make sure they aren’t corrupted, and puts any corrupted files in a Temporary Collection in the Catalog panel. I’ve never seen a corrupt DNG file, so I don’t think it happens often.
This ability to check DNG files to see if they are corrupted is another benefit of the format.
What if my camera uses the DNG format?
Some Leica and Hasselblad cameras already save files in the DNG format. There’s also at least one Pentax camera that gives you the option of using either DNG or Pentax’s own Raw format (.PEF). Some iPhones and Android smartphones also use DNG.
This seems convenient, but bear in mind that camera generated DNG files don’t contain Fast Load Data. Only DNG files created by Adobe software do so.
The case against using DNG in Lightroom
The case for DNG is impressive but there are some situations when DNG might not be the right solution for you.
It extends the time required to import your photos into Lightroom. If you’re in a hurry, you may choose to avoid using DNG to save time. Otherwise, get into the habit of importing photos when you have something else to do while your computer gets on with it. If you’re importing lots of photos you can even leave it to run overnight.
Not all applications open DNG. If you ever use, or think you may use, software that doesn’t recognize the DNG format you should probably stick with your camera’s native Raw format.
Smart Previews are even faster than DNG in the Develop Module. You can save yourself a lot of time during the import process by setting Previews to Standard and building Smart Previews. This is much quicker than converting your files to DNG. The Develop module runs faster with Smart Previews that it does with DNG files.
This is so effective that I now convert all my photos to Smart Previews and have stopped converting my photos to DNG. I can work without connecting my hard drive to my computer and the Develop module is much faster.
If you choose to try this workflow there are a couple of points to bear in mind.
If you have Lightroom 6.7 / CC 2015.7 or later you can set Lightroom to use Smart Previews in the Develop module at all times. Go to Preferences > Performance and tick the Use Smart Previews instead of Originals for image editing box to enable this feature. You’ll need to restart Lightroom for it to take effect.
You may be better off using DNG if any of the following apply.
1. You like to zoom in to 100% to when developing photos (portrait retouching is a good example of where you might want to do this). Smart Previews are smaller (2540 pixels along the longest edge) and that restricts how far you can zoom in. You need to connect the hard drive containing your photos to your computer to zoom in to a 1:1 view. At this magnification Lightroom builds its own preview instead of using the Smart Preview (which is too small). You need DNG to maximize Lightroom’s speed.
2. You have Lightroom 6.6 / CC 2015.6 or earlier. In this case Lightroom only uses Smart Previews in the Develop module when you disconnect the hard drive containing your photos from your computer. There are two situations where this creates an awkward workflow.
You regularly export photos to Photoshop or plugins. You can only do this when the hard drive containing your photos is connected to your computer. In this case Lightroom stops using Smart Previews in the Develop module and reverts back to regular previews. Again, DNG is required to maximize the speed at which Lightroom works.
You use the merge to HDR or panorama tools. If you disconnect the hard drive containing your photos from your computer and you have Lightroom 6.7 / CC 2015.7 or later then Lightroom can merge Smart Previews. But the resulting image is limited by the smaller size of Smart Preview files.
You can learn more about Smart Previews in my article The Ultimate Guide to Using Smart Previews in Lightroom
What to read next
Read these articles next to learn more about using the Develop module in Lightroom.
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