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Author Topic: Color Picker readout in % - Can I change this to 0 - 255?  (Read 4506 times)

Dinarius

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Color Picker readout in % - Can I change this to 0 - 255?
« on: January 21, 2011, 08:37:59 am »

I'm just starting out with LR3 and I'm used to reading Gretag CCs using the 0-255 scale.

I notice that LR3 uses a % scale.

Can I change it to make it read the other way?

Thanks.

D.
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John R Smith

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Re: Color Picker readout in % - Can I change this to 0 - 255?
« Reply #1 on: January 21, 2011, 09:39:36 am »

I notice that LR3 uses a % scale.

Can I change it to make it read the other way?


I don't think so. It threw me at first, because like you I was used to 0-255. But now I find it easier to think of 96 as nearly white (I'm working in B/W, not colour). Mid-gray is 50, and so on. It actually seems a bit more logical as a luminosity scale.

John
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digitaldog

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Re: Color Picker readout in % - Can I change this to 0 - 255?
« Reply #2 on: January 21, 2011, 10:25:56 am »

Can’t be changed. And its based on a rather “odd” color space (Melissa RGB) that has no relationship to any space you’ll end up with outside of LR. Still, its useful and I think a bit more intuitive than 0-255. Equal values are neutral. I would like to see a switch to 0-255 based on a color space I select. Maybe in V4.
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Dinarius

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Re: Color Picker readout in % - Can I change this to 0 - 255?
« Reply #3 on: January 21, 2011, 11:59:16 am »

Thanks.

That's a major minus, in my opinion.

I could practically quote you the RGB numbers for every patch on a Gretag CC. I do a lot of museum and gallery work.

So, unless I can find a workaround, I may be going back to ACR.

D.
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digitaldog

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Re: Color Picker readout in % - Can I change this to 0 - 255?
« Reply #4 on: January 21, 2011, 12:23:19 pm »

I could practically quote you the RGB numbers for every patch on a Gretag CC. I do a lot of museum and gallery work.

Really, for all well supported RGB working spaces?
Even if you had the 0-255 values in LR, you’d have to relearn all the values again. Its using ProPhoto primaries with a 2.2 TRC. Its not a space you can easily get out of LR (you’d have to first build that color space).
The usefulness of the values, either in 0-255 (which isn’t what the numbers actually represent being high bit) or percentages is the relationships between them not the exact values.
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dmward

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Re: Color Picker readout in % - Can I change this to 0 - 255?
« Reply #5 on: January 23, 2011, 11:14:29 am »

It took me about 15 minutes to create a chart in Excel that has the 0-255 values and the corresponding percentages.
I used ProPhoto numbers since they seem to be the closest.
White is about 94%, black is about 14%, etc.

I keep a printout handy just in case I want to check a specific square.
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Dinarius

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Re: Color Picker readout in % - Can I change this to 0 - 255?
« Reply #6 on: January 24, 2011, 11:35:01 am »

As a workaround, can I create a profile for a specific setup (using a Gretag Macbeth chart) either with the old Fraser method in ACR, or using the DNG Profile Editor, and then make it "visible" in Lightroom's Camera Calibration/Profile tab?

If so, how do I save it?

On a related point, does others think that Adobe are taking colour control in Lightroom seriously given the use of percentages and Melissa RGB? After all, isn't it a case of if it ain't broke etc.....?

Thanks.

D.
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digitaldog

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Re: Color Picker readout in % - Can I change this to 0 - 255?
« Reply #7 on: January 24, 2011, 01:46:41 pm »

As a workaround, can I create a profile for a specific setup (using a Gretag Macbeth chart) either with the old Fraser method in ACR, or using the DNG Profile Editor, and then make it "visible" in Lightroom's Camera Calibration/Profile tab?

Nope. Not if I understand the question about using Calibration pane. The numbers in the read-out are what they are.

Quote
On a related point, does others think that Adobe are taking colour control in Lightroom seriously given the use of percentages and Melissa RGB? After all, isn't it a case of if it ain't broke etc.....?

Yes and no. I have no issue with the scale, I think its more intuitive anyway. Being forced to get values of MRGB, yes. I’d prefer the product work like ACR.
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Dinarius

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Re: Color Picker readout in % - Can I change this to 0 - 255?
« Reply #8 on: January 25, 2011, 03:54:53 am »

Thanks again for the reply.

Another question........ :)

In the DNG editor, what space are the RGB readings? I've got Schewe's RWCR book and it goes into using the DNG editor in great detail, but it makes no mention that I can see of the colour space.

The readings I'm getting are very small numbers. e.g. In ACR I would expect a Gretag blue to be 53, 64, 143.

In the DNG editor, the readings are in the twenties. e.g. 25, 27, 29, or similar (I'm not in front of that computer right now, so I can't say exactly.) In order to edit a Gretag CC, I obviously need numbers to aim for, so I need to know what these should be.


> dmward: Where did you get a list of the Adobe RGB equivalent percentage readings to the 0-255 RGB numbers? Thanks.

D.
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dmward

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Re: Color Picker readout in % - Can I change this to 0 - 255?
« Reply #9 on: February 14, 2011, 09:59:10 am »

The percentages were calculated from a table with the 0-255 values.
There are several sources for the 0-255 values in various color spaces. I think X-Rite has some of them on their site a search will offer other sites with the material.
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Dinarius

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Re: Color Picker readout in % - Can I change this to 0 - 255?
« Reply #10 on: December 15, 2011, 10:34:57 am »

Bringing this to the top with a new question.....

I have TIFF files of GretagMacbeth Color Checkers. They are from www.basICColor.de and are created from samples of many charts and then saved in different colour spaces.

If I open them in CS5, I can read off the 0-255 values and they are as given, whether in Adobe RGB or sRGB.

Similarly, if I open the sRBG file in LR3, I can read off percentages, which I have made a note of.

My question is this.....

If I correct a Gretag CC in a photograph to match the sRGB/% values that I have noted, and if I then save out the corrected file in Adobe RGB, will the saved file be as if I had been editing in Adobe RGB all along?

Thanks.

D.


Edited: I've pretty much answered my question (I think!  ;) ) and in a good way. Here's what I did.....

1. I opened the sRGB Gretag CC in CS5 and assigned the sRGB profile to it. The colour picker values were exactly as I would expect of an sRGB CC.

2. I then saved it as a TIFF.

3. I then opened that sRGB TIFF in LR3 and saved it back out to another location using my LR 3 settings - i.e. 16bit TIFF/ Adobe RGB.

4. I then opened that new TIFF in CS5. The readings were exactly as I would expect of an Adobe RGB Gretag CC.  :)

So, LR 3 is converting the MRGB values it displays to Adobe RGB (or whatever you choose).

Now all I need are % MRGB values for the Gretag CC that I can correct to.

A quick Google brought me to these.......

http://lagemaat.blogspot.com/2008/06/srgb-tone-curve-and-lightroom-color.html

If they're OK, then fine. If not, I'd be grateful for another link.

Thanks.

D.

Ps. But, does LR3 have an ACR-type colour picker that allows you to perform a Bruce Fraser type calibration by picking values from the colour patches in a Gretag CC? Coz, if it doesn't.........I've been wasting your time.  ;)

« Last Edit: December 15, 2011, 12:19:04 pm by Dinarius »
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