(http://www.johnkoerner.org/histo2.jpg)[/center]
Does this mean I have no shadow clipping, no highlight clipping, but DO have color clipping that is outside the Adobe RGB color space?
Does this mean I have no shadow clipping, no highlight clipping, but DO have color clipping that is outside the Adobe RGB color space?
Scott, thank you for the info too (and glad you like the photo ;D ). Does the Photoshop histogram tell more a complete story about gamut than does Lightroom? Or is there some other means by which I should analyze the gamut in PS?
Histograms aren't helpful for gamut or gamut clipping info.
With Lightroom’s histogram referring to this sRGB-TRCed ProPhoto-gamut Melissa space,
it seems to me hard to predict if saturation clipping would occur upon conversion to smaller Adobe RGB.
But then I’m not a Lightroom user, and the question may fit to the current discussion in the LR forum on its Clipping Indicators (http://www.luminous-landscape.com/forum/index.php?topic=56808.0).
Peter
Totally incorrect (just look at my example). Photoshop's soft proofing capabilities are only useful to find out if clipping occurs at converting to an output colour profile.
Totally incorrect (just look at my example). Photoshop's soft proofing capabilities are only useful to find out if clipping occurs at converting to an output colour profile. For any other situation (increasing saturation for instance), the histogram is the best tool.
The colors seen in the histogram are useful to see the gamut clipping of one, two (saturation) or more channels (white/black all three).
I think you and Guillermo are taking this conversation out of context for it to be constructive to the OP.
I think you and Guillermo are taking this conversation out of context for it to be constructive to the OP
Your example shows 'white point clipping', or we could even call it 'dynamic range clipping' which is quite different from color saturation clipping or gamut analysis. I'll rephrase my previous statement as "Histograms aren't helpful for determining color saturation clipping."
Photoshop's soft proofing is useful for perhaps more than you think, including comparison to a working space like the original poster specifically asked about. If he wants to see if his images has out of gamut colors relative to AdobeRGB he can find this out with those tools.
What you see there is not any kind of clipping, is just that the Y-axis scale in which LR decided to show you the histogram doesn't reach its maximum, so it shows you a truncated version of the complete histogram. But it's just a matter of plotting, nothing related to the content of your image gamut.
The following image:
xxx
has the following histograms (left Photoshop, right complete histogram):
xxx
As can be seen, PS truncates the Y axis of the graph in order to make the plot more representative.
To analyze gamut clipping in the histogram, just look at histogram ends: in my picture, the Glencoe landscape in the Highlands was so intensely green that sRGB didn't manage to encode it, clipping the blue channel in 0.
For photographers who never heard about histograms, I think it's a good idea to look at the statistical concept of histogram (http://en.wikipedia.org/wiki/Histogram), much wider that its particular application to photography.
Regards
Histograms aren't helpful for gamut or gamut clipping info. Photoshop's soft proofing capabilities are designed for help analyze gamut clipping. View>ProofSetup>Custom... and View>GamutWarning are the two tools worth getting to know if you're not familiar with them already.
Quite true, but the histogram indicates that the scene is of rather low contrast, and setting of better black and white points would drastically improve the image. With ACR one can see gamut clipping in the chosen color space, but with LR one would have to export to ProPhotoRGB and use Photoshop's soft proofing tools.
Regards,
Bill
I’d agree with you too. The colors seen in the histogram are useful to see the gamut clipping of one, two (saturation) or more channels (white/black all three). This tool is more useful in ACR because you can see the effect of gamut clipping as you change the RGB encoding options (toggle from sRGB to ProPhoto RGB as an example). Unfortunately, in LR, you get to see clipping based on ProPhoto primaries and if you export in anything but ProPhoto, the resulting histogram is different and you probably clipped saturation “blindly”.
To answer the OP’s question about all three channels clipping, I would suggest he alter the various rendering controls (Exposure, Blacks) to push the histogram out and see the results of the image. IOW, having a fixed histogram appearance can often make the image appearance ugly and awful! Edit images to appear as you desire on a calibrated and profiled display, not to produce a certain appearance of a histogram. Also using the clipping indicators (Alt/Option key) as you drag various sliders (again, Exposure, Blacks, Recovery) can be useful to see not only what is and isn’t clipping but where you might want to set the end of the tone scale and then viewing the image. Do you have and do you want a highlight that’s close to clipping (a specular?). Do you want to block up shadow detail as part of an artistic expression of the image? Look at the work of Greg Gorman and see how his style has no regard for shadow detail by design. There is no rule that says because you have shadow detail, you need to render and express it in your image. Clip it to death if you like that rendering.
Acutally, the ACR histogram is quite helpful in detecting saturation clipping. This is demonstrated in the two histogram previews shown below. In the first histogram with sRGB the red channel shows severe clipping. This is totally removed by using ProPhotoRGB.
OK, yes, good example. LR's histograms, as the OP asked about, won't show this. I'll rephrase my previous statement as "LR's Histograms aren't helpful for determining color saturation clipping, and ceiling scraping isn't a concern."
Jack,
You set the black point to your liking - this might involve clipping shadows to produce a higher contrast image.
To break it down using simple language:(http://www.johnkoerner.org/histo.jpg)
(http://www.johnkoerner.org/histo2.jpg)
Does this mean I have no shadow clipping, no highlight clipping, but DO have color clipping that is outside the Adobe RGB color space?
Forgive the simplicity of the question, but I am trying to better understand what the histogram is telling me.
Would this be an instance where, say, a "print" rendered in the ProPhoto color space would give me a substantially more "vivid" output, color-wise, than what I am seeing on my Adobe RGB screen?
Thanks for any help,
Jack
.
The Lightroom histogram doesn't tell you anything about how this image will render when converted to Adobe RGB (1998), any other color space (including ProPhoto RGB)…
Ellis, I wonder if you would elaborate on this. It's my understanding that the histogram in lightroom is based on ProPhotoRGB (or the Melissa RGB variant) and the histogram would in fact tell you quite a bit about the image in the prophoto space.You are correct: it does tells you a lot about tonal distribution in ProPhoto RGB , but just not the whole story. For starters "Melissa RGB" (Lightroom's native color space ) is based on ProPhoto RGB but ProPhoto RGB has a gamma of 1.8 while Melissa's uses a more perceptually uniform 2.2 gamma. I believe ( I don't have my notes i nfront of me) that Melissa RGB's tonal response is modeled on sRGB's.
Yo uare correct: it does tells you a lot about tonal distribution in ProPhoto RGB , but just not the whole story. For starters "Melissa RGB" (Lightroom's native color space ) is based on ProPhoto RGB but ProPhoto RGB has a gamma of 1.8 while Melissa's uses a more perceptually uniform 2.2 gamma. I believe ( I don't have my notes i nfront of me) that Melissa RGB's tonal response is modeled on sRGB's.Melissa is somewhat confusiong in Lightroom. The working space is linear (gamma = 1), but the histograms and info readouts are in terms of an sRBG tone curve, which is gamma 2.2 with a linear segment for the deep shadows. The tonal distribution for a linear space is suboptimal, since the quantization steps are too large for shadow values (see encoding (http://www.anyhere.com/gward/hdrenc/hdr_encodings.html), by Greg Ward, Figure 2 and text). Using a gamma of 2.2 improves the quantization in the shadows, but a linear segment is still needed for the deep shadows as the quantization step approaches infinity as the luminance approaches zero.
Melissa is somewhat confusiong in Lightroom. The working space is linear (gamma = 1), but the histograms and info readouts are in terms of an sRBG tone curve, which is gamma 2.2 with a linear segment for the deep shadows. The tonal distribution for a linear space is suboptimal, since the quantization steps are too large for shadow values (see encoding (http://www.anyhere.com/gward/hdrenc/hdr_encodings.html), by Greg Ward, Figure 2 and text). Using a gamma of 2.2 improves the quantization in the shadows, but a linear segment is still needed for the deep shadows as the quantization step approaches infinity as the luminance approaches zero.Thanks for that explanation Bill.
Regards,
Bill
The tonal distribution for a linear space is suboptimal
That's true only for an integer encoding. Floating point formats fix this, since they devote a number of bits to the significant digits and some bits to the exponent, so representation of deep shadows is as good as highlights.
The histogram only shows colors that are available to it - which is the monitor color space usually close to sRGB