Today’s Question: Arthur Morris asked a question in his blog about checking the RGB values in Lightroom. When I use the eyedropper tool it shows a value in percentage. Is there a way to show the actual RGB values?
Tim’s Quick Answer: It is possible to view RGB values in Lightroom as 8-bit per channel values (0 to 255) rather than as a percentage (0-100), but only by enabling the Soft Proofing display in the Develop module. It is critical to keep in mind that the Soft Proofing preview (and therefore the RGB value presented) are based on the specific profile and settings you establish for the soft proofing display, and thus don’t necessarily represent the actual final RGB values for the image.
More Detail: When you move your mouse over the image in Lightroom’s Develop module, the RGB values for the pixel under the current mouse position will be displayed below the histogram at the top of the right panel. Those values are displayed as a percentage rather than the range from zero to 255 that are commonly used to describe RGB data.
You can turn on the Soft Proofing checkbox on the toolbar below the image preview area to have the RGB values shown as 8-bit per channel RGB values (0-255) rather than as percentages. However, those values will be based on the settings established for soft proofing, meaning the values are only meaningful in the context of a specific printer, ink, and paper combination.
What that translates to is that I recommend only using the Soft Proofing option if you are indeed preparing a photo to be printed, and you need to evaluate the output you can expect based on a specific printer, ink, and paper combination.
For more general purposes, I recommend leaving the Soft Proofing checkbox turned off while applying adjustments to your images and evaluating the overall photo. That means you’ll see RGB values as a percentage rather than the 8-bit values you might be accustomed to. But a little bit of math can provide a translation, and with a little bit of experience you’ll gain an understanding of how the values relate to each other.
It is worth noting that the 8-bit values themselves aren’t a full representation of the information in your images, assuming we’re talking about RAW captures, for example. Lightroom actually processes your photos (in the Develop module) with a 16-bit per channel workflow. In other words, the actual underlying values for a photo could range from zero to 65,536, not just zero to 255.
I should also hasten to add that I don’t agree with Arthur Morris’ suggestion that the brightest value for an image should have RGB values of around 240 or so. As far as I’m concerned there is no reason to restrict your processing of a RAW capture to avoid white values that are brighter than a specific value. With some print workflows there used to be (and in some cases still is) a reason to keep the whites from getting too bright. That isn’t the case today for most workflows. Restricting your bright values arbitrarily is only limiting the dynamic range of your final image, without providing a true benefit.