Make Lightroom Faster by Using DNG

Make Lightroom Faster by Using DNG

Using DNG to Make Lightroom Faster

A question that often arises is how to make Lightroom faster. On my computer the biggest bottleneck comes when I’m looking at images in the Library module’s Loupe view or in the Develop module. Even images for which Lightroom has created 1:1 previews can take a few seconds to render properly. This may not sound much, but it’s annoying when flicking through images trying to decide which ones to process. It’s even more frustrating when zooming in 100% to check details which are important to me, such as that the eyes are in focus in portraits (above).

Luckily, there’s a relatively easy fix – and it doesn’t involve upgrading your computer or adding RAM (although those things may help). You can put it into action without spending money, and you should see a benefit regardless of how low- or high-spec your computer is.

Fast Load Data

The key is to convert your Raw files to the DNG format. You may not like the sound of it (I’ll explore some of the pros and cons later on the article) but it really does help. Why? It’s all to do with something called Fast Load Data – a partially processed preview of the image that enables Lightroom to render previews faster than it can from a non-DNG Raw file or a DNG file without Fast Load Data.

The net result of converting your Raw files to DNG and including Fast Load Data is that it enables Lightroom to rapidly display previews of your images. That means less time waiting and less frustration for you.

Converting to DNG

Using DNG to Make Lightroom Faster

The best time to convert your Raw files to DNG is when you import them from your camera’s memory card. To ensure you get the full benefit of using DNG, make sure you go to the File Handling tab in Preferences and tick the Embed Fast Load Data box (above). Do this before you convert any Raw files to DNG, otherwise you will miss out on the speed increase that DNG can give you.

These are the key steps to follow during the import:

Using DNG to Make Lightroom Faster

  • Select the Copy as DNG option in the Import window (above). This tells Lightroom to copy the Raw files from the memory card to the specified folder on your hard drive, converting them to DNG as it does so.

Using DNG to Make Lightroom Faster

  • Set Build Previews to 1:1 in the File Handling panel (above).

Using DNG to Make Lightroom Faster

  • After the import, go to the Catalog panel and select Previous Import. Then go to Library > Validate DNG files. Lightroom checks the files you have just imported and converted to DNG to ensure they are not corrupted. Any corrupted files are placed in a Temporary Collection that appears in the Catalog panel. I’ve yet to see a corrupted DNG file, so I don’t think it happens often.

Other Pros and Cons of DNG to Make Lightroom Faster

If you read around on the topic of DNG you will find that opinion varies widely as to whether it is good idea to convert your Raw files to the format.

Note that some Leica and Hasselblad cameras use the DNG format already – so if you are lucky enough to own one of those then the discussion is irrelevant. There’s also at least one Pentax camera that gives you the option of using either DNG or Pentax’s own Raw format (.PEF). If you own one, selecting DNG saves you having to do it at the import stage (if you choose to use DNG).

Bear in mind that camera generated DNG files don’t contain Fast Load Data – only DNG files created by Adobe software do so.

First, the case against using DNG:

  • It takes longer to convert your Raw files to DNG than it does to simply copy them. This is true – but as long as you’re happy to go away and do something else while your computer gets on with it, it won’t be much trouble. I often leave mine running overnight, especially if I have a lot of images to import and convert.
  • Not all applications open DNG. If you ever use, or think you may use, your camera maker’s proprietary Raw conversion software (such as Canon’s Digital Photo Professional) you should probably stick with your camera’s native Raw format, as the majority of these programs don’t recognise DNG. Check the documentation if you are unsure.

Using DNG in Lightroom

Using DNG purely to increase Lightroom’s speed is little use if you don’t use 1:1 previews. By default Lightroom discards 1:1 previews after 30 days (you can change that under the File Handling tab in Catalog settings), so even if you tell Lightroom to create 1:1 previews when you import your images, they will eventually be deleted by Lightroom. Not sure if an image has a 1:1 preview? Just select the image (or images) and go to Library > Previews > Build 1:1 Previews (above). Lightroom will build 1:1 previews for any selected images that don’t currently have them.

Now, some other benefits of DNG:

  • DNG files are smaller than other Raw formats. Converting your Raw files to DNG upon import reduces the amount of space they take up on your hard drive by up to 20 percent. That could be useful, especially for high volume shooters.
  • You may own a new camera with Raw files that aren’t recognised by your version of Lightroom or Adobe Camera Raw (ACR) if you are using Photoshop (not all readers will have upgraded to the latest versions). In this situation you can use Adobe’s free DNG Converter application to convert them to DNG. Adobe usually updates the DNG Converter to work with files from new cameras before Lightroom and ACR.
  • Embedded file verification. A DNG file contains a checksum that enables Lightroom to check if the original source data is corrupted. DNG is the only Raw file format that does so. It means that you can check your images after you have converted them to DNG to make sure there are no issues with corruption.

Mastering Lightroom Book One: The Library Module

Using DNG in Lightroom

My latest ebook Mastering Lightroom Book One: The Library Module is a complete guide to using Lightroom’s Library module to import, organise and search your photo files. You’ll learn how to tame your growing photo collection using Collections and Collection Sets, and how to save time so you can spend more time in the Develop module processing your photos.

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Andrew S. Gibson is a writer, photographer, traveler and workshop leader. He's an experienced teacher who enjoys helping people learn about photography and Lightroom. Join his free Introducing Lightroom course or download his free Composition PhotoTips Cards!

Some Older Comments

  • Josh October 3, 2013 12:14 am

    This is something I might try for some of my larger photos which can be a pain to process. I assume Photoshop can handle DNG images right? For instance if I import 5 pictures for a panoramic as DNG files and then send them to Photoshop for stitching it'll be able to handle it? I typically save the output image from Photoshop as a tiff file and then import the new file to Lightroom for final processing.

    Great read!

  • Juan Castillo October 2, 2013 10:46 pm

    Good points. But the time lag of Lightroom previews have never bothered me much. I'd rather stick to RAW :).

  • Vit Kovalcik October 2, 2013 04:39 pm

    There is also another potential drawback: When working with RAW, the metadata modified by Lightroom are written into the sidecar XMP file, which is very tiny. On the other side, with DNG the metadata are written into the file itself.

    This may present few problems - it is more risky (though this is probably not really an issue), LR has to write much more data on disk and doing a perpetual backup is harder, because for any small change in keywords, you need to backup/copy/upload the much larger DNG and not only the small XMP (several hundreds times smaller) .