This is one of the most common questions asked by Lightroom users. You import your images, see the thumbnails appear, but if you wait a few seconds you notice that the thumbnails change. The changes can be to tone, contrast, or color. What gives?
When we photograph with a digital camera, even if we shoot raw files, our camera creates a small JPEG file — this is what we see on the camera LCD screen. Unlike a raw file, this file is interpreted — it has our camera manufacturer’s interpretation of color applied, as well as any JPEG settings set on your camera — color space, contrast, saturation, noise reduction, sharpening, etc. None of these settings are applied to your raw files, but they are to the preview JPEGs.
Because we prefer instant gratification, when Lightroom is importing images it first shows us these JPEG thumbnails that our cameras generated. Then it goes on to render its own JPEG thumbnails, based on the raw file, with Adobe’s interpretation of color, and minus all the settings mentioned above.
To most people I advise: just don’t look until it is done! Then you won’t worry about the difference. I don’t — I accept the Adobe rendering of the raw file as I see it and work from there to make the image look great.
To those that really like the look of their camera’s JPEGs and want to replicate the look with their raw files, or work their raw files in a camera manufacturer proprietary raw converter because of this issue, Adobe has provided camera-specific profiles that attempt to match what your various camera settings produce. In the Develop module, under the Camera Calibration panel in the bottom right, click on the drop-down next to Profile, and choose one of the Camera profiles. If there is one you want to apply often, consider creating a preset. Or, if there is one you always want applied to your images, set it as the new default — change the profile (and nothing else!), then go to Develop> Set Default Settings. (Note: In the camera calibration tab you will only see camera profiles for raw files. JPEGs will only list one “embedded” profile — JPEGss have already been “cooked”, so it is too late to change your mind on color rendering.)