Adobe DNG Fast Load Data & Smart Previews

So every time you convert to DNG you’ve been checking the option to include Fast Load Data.  Anything you can do to speed up “walking images” (moving from one image to the next in the Develop module) should help, right?

Screen Shot of the Embed Fast Load Data option in the Convert to DNG dialog for Adobe Lightroom.

Over time, you’ve also correctly discovered that rendering Smart Previews speeds up walking images.  When Lightroom sees that a Smart Preview is present, even when the full RAW/DNG file is available, it will load the Smart Preview into Develop first and “light up” the control sliders, then continue silently loading the full file in the background.  The result is the appearance of faster image load times.

Under these circumstances, the Fast Load Data is completely redundant.  The presence of the Smart Preview provides 100% of the performance benefit of the Fast Load Data, plus some additional performance.  In fact, when a Smart Preview is available, Lightroom completely ignores the Fast Load Data, so it provides no benefit at all.  If Smart Previews are a normal part of your workflow, you can stop embedding Fast Load Data, and save both a little bit of file size, and a little bit of DNG conversion time.

Do you use Fast Load Data?  Smart Previews?  Neither?  Have you been using both?  Comment below.

4 thoughts on “Adobe DNG Fast Load Data & Smart Previews”

  1. HI.

    About “Embed Fast Load Data”

    We know from API that “Embed Fast Load Data” will load only in LR in Develope module, but question is, how many time LR load this data?
    Only first use (open) in develope module, or all time?

    I have some information from WWW, that this function us only first open file in LR (DEV), and again open file will read from LR CACHE?


    1. Hi Slawek.

      The very first thing the develop module looks for is a smart preview. If that’s available, then it trumps everything else. Develop loads the SP first, then the original file. Smart Previews completely negate the value of fast load data, as even when fast load data is present, the Develop module never touches it if it has access to a SP.

      If there is no SP, but there is Fast Load data, then it reads that Fast Load Data. This is true even if there is data in the Camera Raw Cache (FLD gets priority.) If there’s no SP, no FLD, but there is data in the Camera Raw Cache, then the Cache gets read.

      If you want to see an excellent visual flowchart of the process, I highly recommend Victoria Bampton’s ( book on Lightroom 6.

      I was actually present for the conversation where she fact checked the flowchart with the engineers, so I’m confident in its accuracy.

  2. Hi.

    Thanks for Your reply.
    But I’ve one more question .

    If i don’t have SP. But only DNG with FLD.
    When I open this DNG in develope module… first data will read from FLD => ok. But what will happen, when i switch to another photo and come back to this foto again (before opened). This data will read from LR CACHE or again from FLD (from file)?

    This is really important for me, because i’m going to prepare coverting 25 000 photos from .RAW to .DNG .

    So, if LR use FLD only to first preview (open) file , but again preview will use LR CACHE this is good for me…

    Any bytes is important, 1 files is not problem but 25 000 files is really different . I don’t know if make a sens include FAST LOAD DATA to DNG.

    Thanks Sławek.

    1. Lightroom always prioritizes FLD over cache, even when ACR cache data exists. Embed FLD if you don’t want to use smart previews.

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