Viewing L*A*B values during soft proofing

[David Eckels]

After watching the Charles Cramer videos I learned the L*A*B values can be viewed for the LR histogram. Can this be done during soft proofing once a virtual copy (proof copy) is created? Obviously the copy can be viewed with soft proofing turned off and L*A*B values reappear, but I don't think it is the same. It would sure help in fine-tuning an image for printing. But then again, perhaps it doesn't matter if the Proof Copy seems visually close to the original under soft proof conditions.

Hope this makes sense.

[Mark D Segal]

After watching the Charles Cramer videos I learned the L*A*B values can be viewed for the LR histogram. Can this be done during soft proofing once a virtual copy (proof copy) is created? Obviously the copy can be viewed with soft proofing turned off and L*A*B values reappear, but I don't think it is the same. It would sure help in fine-tuning an image for printing. But then again, perhaps it doesn't matter if the Proof Copy seems visually close to the original under soft proof conditions.

Hope this makes sense.

No. The Lab readout only works without softproof activated.

[digitaldog]

The values are based either on the underlying color space used for processing (then converted to Lab for the readouts) or the values based on the soft proof profile used. There's little if ANY need to view Lab values based on the output color space!
Lastly, there are Virtual copies where you can view Lab values and Proof copies where you can't. Both virtual in nature.

[Mark D Segal]

Andrew, to keep this very simple (risk), I think all David is trying to find out, if I understood him correctly, is whether one can see the colour values  reported in Lab once once pushes "S" to get the photo into softproof view. If that'a all he's asking, the answer is no. You get only RGB values in softproof view. At least in my copy of Lr. Have I misunderstood anything?

[digitaldog]

Andrew, to keep this very simple (risk), I think all David is trying to find out, if I understood him correctly, is whether one can see the colour values  reported in Lab once once pushes "S" to get the photo into softproof view. If that'a all he's asking, the answer is no. You get only RGB values in softproof view. At least in my copy of Lr. Have I misunderstood anything?

Yes, a risk with color management discussions. And there's a legitimate reason why Lab values are not available in a soft proof mode.   
Historically, Lab has been way over sold! It's nice to inform folks about when it's useful and when it isn't. 

[David Eckels]

I appreciate what you are saying guys. Mark, you confirmed for me that L*A*B is not available when working with a proof copy in Soft Proof mode. Andrew, if I understand you correctly, I realize that I can create a virtual copy and be able to see L*A*B values in the Development module directly; probably the same as getting out of "Soft Proof" mode and working on a proof version to compensate for the lower dynamic range in the print; but a direct comparison seems not possible.

Thanks for answering my question; no need to waste your time further. Unless, of course I am missing something. BTW and FYI, I am getting VERY close to WISIWIG thanks to what you and others have taught here on LuLa. Thanks for that too.

[Doug Gray]

While you can't read Lab values directly from a soft proof view, there is a way to get the Lab values of a soft proof. I don't often do this but there are times it can be useful. For example if you use Costco to print while controlling color management using DryCreek profiles and you have an I1Pro spectrophotometer. You can measure Lab values on the print and compare them to measured Lab values from the modified image.

Here's how to get an image who's Lab values are what are printed and should be reasonably close to what you measure with a spectrophotometer.

1. Make a copy of the image.
2. Convert the copy to the printer/paper profile selecting intent and BPC as desired to match what you print and softproof.
3. Convert the image back to the same RGB colorspace as the original but select Absolute Colorimetric Intent.

The Lab values of the converted image are the profile's expected Lab values of the printed image. You can place the converted image in its own layer and toggle the layer visibility on and off. Use the info status block to show Lab values.  It can be useful to average a group of pixels (say 11x11) in the picker to more closely match what you would read with an I1Pro which has a physical aperture of 4mm.

[Mark D Segal]

............ I don't often do this but there are times it can be useful. For example if you use Costco to print while controlling color management using DryCreek profiles and you have an I1Pro spectrophotometer. ...............

ROTFL - this made my evening :-)

Do you think there are as many as a handful of people in North America who have an i1Pro, Dry Creek profiles and get their prints made at Costco? (Not to disparage Costco - they can actually produce some pretty decent output, but......)

More seriously - if you were doing this to simulate an external commercial printer, presumably you would need their profile in order to get useful numbers from the process you outline. But having said that, it's not clear to me what one gets out of doing this or why are Lab values useful for such purposes? Softproofing is simulating the behaviour of an output device. In the print world, output devices are normally RGB or CMYK devices, so you would simulate them accordingly. That will cause you to make adjustments to the images. Those adjustments will produce changed colour values that can be measured in a number of different colour "languages" (e.g. Lab for the CMS/profile connection space in the OS), but so what?

[Doug Gray]

ROTFL - this made my evening :-)

Do you think there are as many as a handful of people in North America who have an i1Pro, Dry Creek profiles and get their prints made at Costco? (Not to disparage Costco - they can actually produce some pretty decent output, but......)

More seriously - if you were doing this to simulate an external commercial printer, presumably you would need their profile in order to get useful numbers from the process you outline. But having said that, it's not clear to me what one gets out of doing this or why are Lab values useful for such purposes? Softproofing is simulating the behaviour of an output device. In the print world, output devices are normally RGB or CMYK devices, so you would simulate them accordingly. That will cause you to make adjustments to the images. Those adjustments will produce changed colour values that can be measured in a number of different colour "languages" (e.g. Lab for the CMS/profile connection space in the OS), but so what?

Precisely. Costco is the only large scale retail place I know of where you can get properly managed color prints. Drycreek provides, for free, links to a database of Costco printer (Noritsu and Fuji photo lab) profiles that are kept up to date and specific for the various printers available at most of their stores. Lots of color finicky people use them to get properly color managed prints from a chemical photo printer and they use the profiles to tailor their images.

https://www.drycreekphoto.com/icc/

The outlined process simply provides a mechanism to check that the printer/profiles are producing proper results. If they don't seem quite right it's a way to quantify if the printer did what it's supposed to do.

[Mark D Segal]

That's helpful Doug.