I would like to know if converting my RAW files to DNG will improve the overall speed of Lightroom. The most painful issue is that it takes between 5 and 10 seconds to get my 1:1 image rendered when I zoom on it. I should add that my LR is configured so that it creates the 1:1 preview during importing of the files.

I use a MacBook Pro, Canon's RAWs, Lighroom 3.2. Thanks :)

  • \$\begingroup\$ How much RAM do you have? That seems like a long time... \$\endgroup\$
    – ahockley
    Feb 2, 2011 at 5:53
  • \$\begingroup\$ Are your 1:1 previews set to be discarded after a certain amount of time? \$\endgroup\$
    – LC1983
    Feb 3, 2011 at 22:58

2 Answers 2


All image previews are stored as JPEG files of various sizes inside of a .lrprev file. The loading speed of the preview images will likely not change much if you switch to DNG. The benefit of DNG is that it is an open standard format, and can keep the metadata in the same file as the image data, which simplifies portability. On the flip side, you would incur not only the extra cost of generating 1:1 previews on import, but also converting from your native RAW to DNG raw.

You also have to consider that DNG stores image data in a specific way, using integer values for pixel data. That will generally work for most sensors, however there are some special sensors that use non-square bayer arrays, make use of extra luminance pixels, or might possibly use floating point numbers rather than integers to store individual pixel values. At the very least, if you convert to DNG, you should keep your original RAW images around.

  • \$\begingroup\$ +1 -- or get a camera that does DNG natively... ;) \$\endgroup\$
    – Joanne C
    Feb 2, 2011 at 1:51
  • \$\begingroup\$ I use a canon 7d. Do I have a special sensor? Will I lost something important if I convert everything into DNG? \$\endgroup\$
    – TigrouMeow
    Feb 3, 2011 at 5:15
  • \$\begingroup\$ Also, I don't really care about the extra-cost while generating the DNG and the previews. I just care about "normal" usage. If the image are half size of the RAW, I guess it will be much faster to load too... \$\endgroup\$
    – TigrouMeow
    Feb 3, 2011 at 5:16

Adding to jrista's answer, you can always embed your original RAW file to the DNG file (in the Preferences dialog, under the tab File Handling). This way you can keep your original RAW files. Or you keep them separated, it is up to you.

  • \$\begingroup\$ I think that my issue is the sluggishness of the hard drive in the Mac Book Pro... so I'm not sure embedding the RAW files inside a DNG is going to help much :p \$\endgroup\$
    – TigrouMeow
    Feb 7, 2011 at 7:31
  • \$\begingroup\$ That is correct, it is not going to help much. But my tip was just an addition to jrista's answer about keeping the original RAW and not a tip to speed up Lightroom. \$\endgroup\$
    – cahuk
    Feb 7, 2011 at 17:21

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