For many years now, I've noticed that cameras of different sorts and image editing program display a preview image of different colors from the final image, while it's loading the final image. I've noticed this on several different models of android phones, as the photo app was loading the image I had taken; I've also noticed this on the LCD screen on DSLR cameras, including Pentax and Nikon models, and also in Lightroom, which the the main desktop photo editing program I use.

After all this time, it's bugged me-- why is this so? Usually the preview images appears to have "better" or more saturated colors-- it seems to be the "human-friendly" version that phones deliver to consumers who want good-looking images over color accuracy.

Here are some screenshots from Lightroom CC. Notice that the first image, you'll see the loading... text pop-up over the image, and at a glance, the image seems to skew bluer. The second screenshot has the image completely loaded, and it doesn't have as much blue as the preview loading image.

These are freshly imported NEF images from my Nikon, so I don't suspect any sort of jpeg progressive rendering.



What is going on here?


My understanding is that the preview image is the embedded JPEG within the NEF file. Therefore, my guess is that you're initially seeing the JPEG and then the unedited NEF file.

  • This is the default behavior in darktable. The embeded jpg is used until you make changes then I think the software's database thumbnail is used showing your edits.
    – dmkonlinux
    Mar 6 at 5:30
  • The NEF file as displayed on the screen isn't "unedited", it's just been "edited" (i.e. processed) by a different set of instructions than those that create the JPEG preview from the same raw data. Neither interpretation, nor any of the other near countless possible interpretations of the raw data, is more legitimate than the others. No interpretation is more implicit in the original raw data. Unless you are viewing a very dark image of gray scale pixels in "checkerboard" patterns based upon which color filter was in front of each, you're not really viewing an "unedited" raw file.
    – Michael C
    Mar 6 at 19:57

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