Lightroom1.1: Histogramm difference after exporting to PS

[fp56gallery]

When I export files from LR 1.1 after having developed them and taken care of

the highlights and darks I find that the highlights and the darks I had

previously cured are again over 255 or below 0. I use Adobe RGB (1998) in both

PS and LR. What could be the reason for this?

Franz

[ellis_vener_photography]

Internally Lightroom uses it's own color space --It has the size of Pro Photo but the response curve of sRGB --not Adobe RGB(1998). This likely accounts for the difference in the histogrm that you are seeing. You can't go below 0 or above 255

[fp56gallery]

Thank you, Ellis, you are right. I thought that I had set the Adobe RGB (1998) colour space in LR. But there is no way to do this in LR, though I would like this possibility.

Franz

[ellis_vener_photography]

Actually you wouldn't as you'd be clipping color your cameras is producing.

[glenbarrington]

Thank you Ellis! Your explanation was the key as to why I just didn't 'GET' Lightroom and color! You've earned a couple of 'attaboys' and an exra pat on the back for that explanation!

 

So LR doesn't REALLY use ProPhoto colorspace! Just KINDA ProPhoto! That may be why my printed photo colors were just KINDA right! Now if I cant get my photos to KINDA good, I'll be set for life!

[godfrey]

LR's "kinda ProPhotoRGB" colorspace seems to be more accurate and flexible than

ProPhoto RGB itself. If you print using a managed color workflow (that is, letting

Lightroom control the print process by using a known good profile for the printer/ink/

paper combination you are printing to, and using a properly calibrated monitor), you

should get very high fidelity between the screen and the paper.

 

When you export for editing in Photoshop, you should export as 16bit PSD or TIFF with

ProPhoto RGB colorspace, and you should have Photoshop set up with ProPhoto RGB

colorspace as the default colorspace. This will provide the highest fidelity transition

between the Photoshop and Lightroom editing environments ... converting to Adobe RGB

(1998) in the process is going to cause some losses as both LR's in-built colorspace and

ProPhotoRGB represent much larger gamuts.

 

Godfrey

[digitaldog]

There's actually two ProPhoto RGB like spaces here. There is the internal processing color

space LR uses. That's ProPhoto RGB primaries using a linear tone response curve. The

histogram and numbers are using ProPhoto RGB primaries and an sRGB tone response

curve. So what you're seeing isn't what you're getting. When you export to ProPhoto RGB,

you're getting of course ProPhoto RGB primaries but with a 1.8 gamma TRC.

 

Note, if you're NOT working with raw files, this may present an issue (still up to debate). If

you import a Tiff in say sRGB and do any LR edits, the image data gets converted to

ProPhoto RGB 1.0 TRC gamma. Then you have to figure out what color space you want on

export. If you start in sRGB, do you want to end up in sRGB? If so, you need to keep track

of your export presets. This could be a bit messy, hence the reason I think using CR or LR

for editing existing rendered images using this approach isn't as clean as it could be.

 

There's no reason that in the future, LR and CR could treat rendered images as they

originally were imported and honor that on export.

[daan_barnhoorn]

@ Andrew

 

From LR help:

"For rendered files such as TIFF, JPEG, and PSD files, Lightroom uses the image?s

embedded color profile to display the image, histogram, and color values. If the image

doesn?t have a profile, Lightroom assumes the sRGB profile, and the image may not look

as expected on your monitor."

 

If I understand correctly, the ProPhotoRGB primaries/2.2 gamma tonal response curve

becomes active only when I use the develop mode in LR. In the library it honors the

original values with rendered files. RAW is treated as AdobeRGB when viewing in the

library.

 

From LR help:

"A color profile is also defined by a gamma value, or more accurately, its tonal response

curve. The tonal response curve defines how tonal values in the raw image are mapped. To

provide useful information in the histogram and RGB value display, Lightroom assumes a

gamma value of approximately 2.2. More accurately, it uses a tonal response curve similar

to the tonal response curve of the sRGB color space."

 

"While Lightroom uses a tonal response curve to provide information for the histogram

and RGB values, it manipulates the raw data before it is tone mapped. Working in this

linear gamma avoids many of the artifacts that can result in working with a tone-mapped

image."

 

When I import an AdobeRGB RAW file into LR, do some editing, and export it as a

AdobeRGB TIFF/JEPG I don't see a different histogram in another program (for example

Capture NX). The only time I saw a different histogram was when I exported an edited

AdobeRGB RAW file as a sRGB TIFF/JPEG. Although in negligeble amounts, the red

highlights were a bit more clipped.

 

Can you explain this to me?

[digitaldog]

>If I understand correctly, the ProPhotoRGB primaries/2.2 gamma tonal response curve

becomes active only when I use the develop mode in LR. In the library it honors the

original values with rendered files. RAW is treated as AdobeRGB when viewing in the

library.

 

Yes (It appears that way, but the numeric feedback is different, 0-100% than Photoshop).

However, if you edit the image, it is converted into ProPhoto/Linear gamma for the edits.

 

Note the 2.2 TRC in sRGB and used here isn't really a gamma curve! There's a small tweak

in the shadow regions so it doesn't follow the gamma formula. This has been spec'ed in

sRGB from day one. The same TRC is used in Melissa RGB used for the Histogram and

numbers (that being the case, and I'll check with Mark Hamburg when he's back from

vacation, if I import a a tiff or JPEG image with a 1.8 gamma, the Histogram and numbers

probably are NOT giving us the actual values).

 

When you import from Adobe RGB (1998) and back out to Adobe RGB (1998), AND apply

an edit, the data will go:

 

Adobe RGB (1998) -> Linear ProPhoto RGB -> Adobe RGB (1998).

 

Try doing this in Photoshop (use the actual ProPhoto RGB profile). Look at the Histogram

before and after this three way conversion. Do they appear the same?

[daan_barnhoorn]

Thanks Andrew,

 

One more thing: what is the gamma of the TRC used by ProPhotoRGB in Photoshop?