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Author Topic: PhotoPro colorspace in LR, export to sRGB  (Read 3124 times)
The View
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« on: May 11, 2007, 10:59:25 PM »
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I just read this in an amazon.com review of LR.

The reviewer stated, that LR uses PhotoPro colorspace and not sRGB. So when you export, he says, you get a different image on another machine working in sRGB.

Another user commented, you can export in sRGB. But the reviewer insisted, even when he exported in sRGB, the image on the other computer would not match what he had on his (I guess he had both his computer monitors calibrated).

He was using windows. Is this a problem of the windows edition. Or did the reviewer just not correctly use the software.

What is your experience with this matter?

Thanks!
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Schewe
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« Reply #1 on: May 11, 2007, 11:56:13 PM »
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Uh, you really, REALLY want to be careful WHO you listen to.

The "reviewer" is totally clueless...

Lightroom uses the Pro Photo chromaticies (the color coordinates) but not the gamma. LR's gamma internally is gamma 1. The histogram display is a tuned sRGB tone curve. But Lightroom's internal color space is _NOT_ "Pro Photo RGB".

And, when exporting, the exported file is in whatever color space you export to. Course, you only have 3 choices...the REAL Photo Photo RGB, Adobe RGB or sRGB. And, those three color spaces are the standard, run of the mill color spaces...

Please, PLEASE be careful who you listen to...and do the world a favor and don't propagate really wrong info. Jeeesh...
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bjanes
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« Reply #2 on: May 12, 2007, 01:17:46 AM »
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Quote
I just read this in an amazon.com review of LR.

The reviewer stated, that LR uses PhotoPro colorspace and not sRGB. So when you export, he says, you get a different image on another machine working in sRGB.

Another user commented, you can export in sRGB. But the reviewer insisted, even when he exported in sRGB, the image on the other computer would not match what he had on his (I guess he had both his computer monitors calibrated).

He was using windows. Is this a problem of the windows edition. Or did the reviewer just not correctly use the software.

What is your experience with this matter?

Thanks!
[{POST_SNAPBACK}][/a]

The whole story above appears very confused and it would be useful to have a link to the review and discussions thereof. As Jeff stated, the reviewer may be wrong or you may have misunderstood the discussion, which is a very easy thing to do since the issue is pretty complicated. If you want to learn more about the internal color space used by Lightroom, there is a discussion in the Lightroom Podcast #8 referenced by [a href=\"http://blogs.adobe.com/jnack/2006/07/lightroom_podcast_8.html]John Nack[/url] on his blog, where he mentions that the Lightroom space has been described as a "bastard space" by some.

Since Lightroom is merely a metadata editor (more technically a parametric editor), it doesn't change the data in the file, but merely keeps track of the parameters that need to be applied to the data to achieve the intended edits. These changes are then applied when you export or print. Fortunately, this whole process is transparent to the user. Although the numbers representing the image are different in the various color spaces, the whole purpose of a color managed workflow is to keep the appearance of the image the same (within limits imposed by the gamuts of the spaces). At first this seems counterintuitive. Lightroom is working in a gamma 1 space, but the histograms and data readouts are for a gamma of 2.2.
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Schewe
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« Reply #3 on: May 12, 2007, 01:33:07 AM »
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Lightroom is working in a gamma 1 space, but the histograms and data readouts are for a gamma of 2.2.
[a href=\"index.php?act=findpost&pid=117066\"][{POST_SNAPBACK}][/a]

Well, no...they are a "tuned" sRGB tone curve which has, as I understand it, tweaks in the shadows. So, it's not a simple 2.2 gamma curve.

Quote
where he mentions that the Lightroom space has been described as a "bastard space" by some.

Internally, it's called Melissa RGB after Melissa Gaul, head of Q&E for Lightroom. We all decided to call it Melissa RGB since there weren't any color spaces named after women.

:~)

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Since Lightroom is merely a metadata editor (more technically a parametric editor), it doesn't change the data in the file, but merely keeps track of the parameters that need to be applied to the data to achieve the intended edits.

True...nothing actually happens to a file until you either export, edit in Photoshop or print. When the Lightroom based adjustments are applied, they are applied in the Camera Raw pipeline, which in Lightroom is Pro Photo RGB chromaticities, a linear gamma and a D50 white point with a histogram read out of sRGB gamma...

Unless you really like sausage making, it's really best if people just eat the darn hot dogs...do you want yours with relish or sour kraut?

:~)
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The View
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« Reply #4 on: May 12, 2007, 01:50:23 AM »
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Uh, you really, REALLY want to be careful WHO you listen to.

Please, PLEASE be careful who you listen to...and do the world a favor and don't propagate really wrong info. Jeeesh...
[a href=\"index.php?act=findpost&pid=117063\"][{POST_SNAPBACK}][/a]

Absolutely. There is so much wrong info and so much unfounded kamikaze opinion on the web you could spin an anti-web out of it. I definitely didn't intend to contaminate this forum with perverse content.

I felt this"reviewer" was very wrong, but I couldn't tell if he truly was or if I only wished he were. ( I should have possibly started the post by writing " I found the following very weird thing... is there anything to it?").

It was an amazon review. (you're possible already lying on the floor because you are laughing so hard. But I heard it's healthy).

I intend to buy Lightroom, and I had to be sure that there were no issues with communicating my photos.

It's all cleared up, and I'm breathing lighter.

Thanks.
« Last Edit: May 12, 2007, 01:51:32 AM by The View » Logged

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The View
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« Reply #5 on: May 12, 2007, 01:53:26 AM »
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If you want to learn more about the internal color space used by Lightroom, there is a discussion in the Lightroom Podcast #8 referenced by John Nack on his blog, where he mentions that the Lightroom space has been described as a "bastard space" by some.
[a href=\"index.php?act=findpost&pid=117066\"][{POST_SNAPBACK}][/a]

Thanks for that url. I can definitely need any good Lightroom info that I can get.
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budjames
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« Reply #6 on: May 12, 2007, 03:38:26 AM »
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Many of the posters should go out and shoot more photos and spend their computer time using LR and other excellent tools we now have and less time posting useless opinions on the web forums.

Jeff Schewe, if you are reading this board, I'm really enjoying the LR podcasts hosted by George Jardine and your tuturials with Michael Reichmann. Thanks for sharing.

Bud James
North Wales, PA
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Bud James
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bjanes
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« Reply #7 on: May 12, 2007, 08:32:45 AM »
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Well, no...they are a "tuned" sRGB tone curve which has, as I understand it, tweaks in the shadows. So, it's not a simple 2.2 gamma curve.

Unless you really like sausage making, it's really best if people just eat the darn hot dogs...do you want yours with relish or sour kraut?

:~)
[{POST_SNAPBACK}][/a]

As [a href=\"http://brucelindbloom.com/index.html?WorkingSpaceInfo.html]Bruce Lindbloom[/url] explains on his web site, the proper sRGB is actually the grafting together of two transfer functions, a linear transform for normalized input values below 0.0405 (about 10 in an 8 bit space, as explained by Norman Koren in the box "for geeks only") and a gamma 2.4 function for higher normalized values. The overall gamma approximates 2.2. I was under the impression that Adobe used a simplified sRGB using a straight gamma curve, which they appropriately call simplified sRGB as Bruce explains. Perhaps you can clarify the situation: what transfer function does Adobe use for sRGB?

Personally, I prefer relish, tomatoes, onions, and mustard.  

Bill
« Last Edit: May 12, 2007, 08:42:01 AM by bjanes » Logged
digitaldog
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« Reply #8 on: May 12, 2007, 09:34:10 AM »
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Color management in Adobe Lightroom:

http://www.ppmag.com/reviews/200701_rodneycm.pdf
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Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
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