Speedy way to import DNG's in to Lightroom

After I finished writing that last post about speeding your workflow with the Adobe Digital Negative Converter, I realized that most of my ideas about this being true were anecdotal. That is, it SEEMED to me that it was quicker going that route but I had never really tested it. Being the good son-of-a-scientist that I am (my dad's a retired nuclear physicist) I decided to run some tests. I started with a set of standardized conditions, carefully controlled the variables, stayed up late in to the night running experiments and took careful notes of the results.

Looking at my data the next morning, I realized: I definitely shouldn't do this late at night. I could barely read my notes.

Must.. have.. coffee.

The results were startling.

It is MUCH faster to first copy your RAW image files to a hard drive on your computer and then use the Adobe Digital Negative Converter to prepare them for importing in to Lightroom, compared with just doing everything in Lightroom.

Here’s what I started with -- a 1 gigabyte SanDisk Extreme III CF card, filled to the very brim with mostly identical photos of the various tubes of caulk in my basement.

I know, there’s probably a good joke in here, but I’m going to leave it alone.

The camera I used for these was a Nikon D200.

What I wanted to end up with was:
  • A set of dng’s on one drive that I’ll use for working in Lightroom
  • A backup set of the original RAW (.nef) files on a second drive.
  • Keywords and iptc information embedded in the files (this was done in Lightroom in all cases)
I started by sticking the CF card in to my Firewire 400 reader and doing everything through the Lightroom interface. There were 63 files on the card, all of them almost identical in size. I instructed Lightroom (using the command, “Open the Pod Bay doors, Hal.”) to copy the files from the reader as DNG files to my eSATA drive and then import them in to the program.

I also instructed the program to build standard previews after import.

And I wanted it to also back up the files to a second drive.

Note that this backup set of files will NOT be converted to .dng files, but will just be a copy of the original files as they came out of your camera.

Click “Import.” Click “start” on the Ipod stopwatch. Make sure you already have some Pink Floyd cranked up, so that you can’t hear the awful sound of “Project Runway” that your wife is watching on TV.

Working with the 63 files this way took a whopping 18 minutes for the whole process. Roughly, that works out to over 17 seconds per file. If I had done a whole wedding this way with, say, 1500 files, I’d be looking at a process that takes over SEVEN HOURS. And in fact that’s been my experience in the past, doing it that way.

Then I tried it another way..

Copying the same set of files to a different folder on my backup hard drive by “dragging them” from the CF card reader to the drive took just 24 seconds.

Then I launched the Adobe DNG converter and converted the files on that backup drive to my eSATA drive, choosing Lossless Compression and Full-Size Previews (thinking that might save some time having Lightroom build the previews.)

The total time to do the conversion was 12 minutes 40 seconds, which was good. Switching to Lightroom, I chose to import the files in place from the eSATA drive and build standard previews. The import only took about 30 seconds, but it took Lightroom just about five minutes to build it’s previews. Apparently it didn’t matter much what I had done with previews in the DNG converter, as far as Lightroom was concerned. Total time: 17:26. Not a huge savings, but it doesn’t hurt. That’s 16.6 seconds per file, so it would still take almost seven hours to do a whole wedding.

At this point, I was feeling like my myth was busted.

This got me thinking, though.. If Lightroom is building it’s own previews no matter what the DNG converter is doing (and I tested this a couple different ways) then maybe I could speed up the process if I chose not to build any previews at all in the Adobe DNG converter.


The conversion of 63 files only took 3 minutes 52 seconds. Importing them in place in to Lightroom then took only 33 seconds for the import and only TWO minutes to build standard-sized previews for all the images. Total time: 6 minutes 26 seconds.

That’s 6.28 seconds per file. On a 1500-file wedding, my total time from CF card to working with the images in Lightroom would be just over 2-1/2 hours.

I’d sure like to pick up an extra 4+ hours of free time on the day after a wedding. That’s time I could spend moaning and taking Advil for my back.

For the purists out there, I should also point out that each time I did this I created a new library in Lightroom so that the program would not be simply relying on cached data to speed the process along.

And on a whim I decided to take a look at the resulting DNG files in Adobe Bridge and also in Photo Mechanic. Surprisingly, working with the files in Bridge was a satisfying experience (I generally don’t mess with Bridge, because I find it maddeningly slow) and the images loaded very rapidly. Bridge builds its own previews, and that didn’t seem to go any slower for the “no-embedded-preview” DNGs than it did for any other file.

In Photo Mechanic it was a different story. Photo Mechanic doesn’t build previews, apparently, but relies on those already embedded in the file. So when I tried to view the file individually (rather than in the contact sheet mode) the most I got was a postage stamp that got pixelated pretty quick when I tried to blow it up. But I usually use Photo Mechanic as a editing tool for files that have already been finished and delivered (like, when I’m getting ready to lose contests) rather than at the start of the process. So that’s okay. But isn’t that tiny preview cute?

My god, it’s full of stars...

1 comment:

Flaming June said...

Thank you so much for taking the time to explain your workflow and the dng advantages. I am new to Raw, and was completely confused about which format I should use and what my workflow should look like. I have been reading how to books - but they just told me how to, not why to.
My next step is to figure out how to automatically delete the ORF file after I convert to DNG. My photos are not nearly important enough to warrant all the triple back-ups (I do update my photos to a separate hard drive weekly.)
anyway, THANKS!! I will be bookmarking your blog for future reading:)