Today’s Question: I was intrigued by your statement that Lightroom Classic sends a “fully rendered image is sent rather than a raw capture” when you edit in Photoshop. Can you explain what the difference is? Isn’t a raw capture a complete image?
Tim’s Quick Answer: A raw capture generally only includes about one-third of the total pixel information for an image, whereas a rendered image contains all the pixel data.
More Detail: Most digital camera sensors only record one of the three colors for each pixel. The “missing” information must be rendered through interpolation, which is handled with post-processing for raw captures and in-camera for JPEG captures, for example.
While most digital cameras are based on the RGB (red, green, blue) color model, all three colors are not captured for each pixel with most image sensors. The most common arrangement is the Bayer pattern, where for every four photosites on the sensor two will capture only green information, one will capture red information, and one will capture blue information.
The fact that the image data is not processed to produce full-color pixel values is the reason these file types are referred to as “raw” captures.
The process of interpolating the image data so that all pixels have full RGB color values associated with them is referred to as “demosaicing”. This is done in the camera for JPEG captures but must be handled by software for raw captures.
If you open a raw capture directly in Photoshop, Camera Raw will be invoked so the image can be demosaiced. If you send a raw capture from Lightroom Classic to Photoshop, the demosaicing is handled by Lightroom Classic based on the adjustmetns in the Develop module, so that a rendered image with complete color information is sent to Photoshop. If you wanted to use Camera Raw to further process the image in the context of sending an image to Photoshop from Lightroom Classic, you would need to use the Camera Raw filter, accessible in Photoshop by choosing Filter > Camera Raw Filter from the menu.
Keep in mind that most of the time the Develop module in Lightroom Classic and Camera Raw in Photoshop include the same features. So, in most cases it isn’t necessary to use Camera Raw if you’re using Lightroom Classic. However, at the moment the Dust feature for Distraction Removal is only available in Camera Raw in the public beta version of Photoshop, which is what caused the original issue to arise in the question I addressed yesterday.
