10 Replies Latest reply on Jul 24, 2014 1:50 PM by RikkFlohr

# How can I convert (or switch) the RGB percent values from the LR histogram into RGB values which are shown e. g. in PS/CameraRAW?

In LR 5.5 (same in previous versions) the RGB values in the histogram are shown in percent (relativ) values. I prefere to see the absolute values, but I can`t find any way to switch. Maybe this option is intentional disabled, because LR works in 16-Bit mode this would result in values up to 2^16. But as i compared the relativ values from LR with the absolute values from PS i run into a conversion problem. The following example shows the differences:

CameraRAW : RGB, 128,0,0

Lightroom: RGB, 43,8%, 19,0%, 6,2%

CameraRAW: RGB, 0,128,0

Lightroom: RGB, 29,8%, 47,5%, 17,5%

Mainly i have two questions:

1. Is there any possibility to change the percent RGB values in LR to absolut values?

2. How can i convert CameraRAW values to LR values (see above)?

• ###### 1. Re: How can I convert (or switch) the RGB percent values from the LR histogram into RGB values which are shown e. g. in PS/CameraRAW?

The values in Lightroom can be either in Percentages or LAB Values.  They cannot be in 8-bit 0-255 range values - except in the Soft Proofing feature.

• ###### 2. Re: How can I convert (or switch) the RGB percent values from the LR histogram into RGB values which are shown e. g. in PS/CameraRAW?

TThe reason that a design decision was made from the beginning of LR to show only the percentage values was that RGB values are dependent on the color space and the LR histogram and numerical readout are derived from the Develop module's display space which is a hybrid color space with ProPhoto RGB primaries and the sRGB TRC. Thus the numerical values in the display would be different from the exported RGB image (in an orthodox space) and it was feared that this would be misleading. When soft proofing was introduced, because it involved converting the display to an orthodox space, it became possible to use the 0-255 scale in that mode.

• ###### 3. Re: How can I convert (or switch) the RGB percent values from the LR histogram into RGB values which are shown e. g. in PS/CameraRAW?

In other words to see the Camera Raw plug-in values, got to Develop, turn on Softproofing, then set your o colorspace to be the same as Camera Raw's, usually sRGB or AdobeRGB or ProPhotoRGB.

• ###### 4. Re: How can I convert (or switch) the RGB percent values from the LR histogram into RGB values which are shown e. g. in PS/CameraRAW?

After enabeling the Softproofing and switch to RGB mode I can see the RGB values. This helps a lot.

Internally LR is using the ProPhoto RGB with sRGB TRC color space, as you wrote. But is there any way to manually calculate the sRGB value of an exported picture out of the RGB percent values which are shown in LR?

• ###### 5. Re: How can I convert (or switch) the RGB percent values from the LR histogram into RGB values which are shown e. g. in PS/CameraRAW?

If you're really good at math and searching in the internet you can look up the formulas for colorspace conversions and maybe get enough things the same as what LR's doing for SoftProofing to do the same calculations, but why.

• ###### 6. Re: How can I convert (or switch) the RGB percent values from the LR histogram into RGB values which are shown e. g. in PS/CameraRAW?

The math is further complicated by the fact that the sRGB TRC is not even a simple gamma 2.2 curve, but rather linear (1.0) in the deepest shadows, roughly 2.2 at the middle and as much as 2.4 in the highlights. Soft proofing is so much simpler.

• ###### 7. Re: How can I convert (or switch) the RGB percent values from the LR histogram into RGB values which are shown e. g. in PS/CameraRAW?

Ok, as i read your comments the calculation seems to be really complicated. I just wants to know this because today there is no benefit for me to see the percentages values. Can you give me an example where it is useful for daily work?

• ###### 8. Re: How can I convert (or switch) the RGB percent values from the LR histogram into RGB values which are shown e. g. in PS/CameraRAW?

You'll get used to it. Why do you feel the need to convert them?

• ###### 9. Re: How can I convert (or switch) the RGB percent values from the LR histogram into RGB values which are shown e. g. in PS/CameraRAW?

I have to agree with john beardsworth; I have gotten used to it, and I haven't yet found a situation where the percent values are unusable

• ###### 10. Re: How can I convert (or switch) the RGB percent values from the LR histogram into RGB values which are shown e. g. in PS/CameraRAW?

Example