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Mark D Segal

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questions about exposure blending from one file
« Reply #20 on: August 15, 2009, 09:59:46 pm »

DPL:

My understanding of the Recovery tool in LR/ACR is that it builds back detail by calculating replacement tones for blown primaries as long as at least one of the primaries is still present in the area to be "recovered".

I'd like to hear more about your proposition that "Recovery seems to be placed too late in the processing chain so that compression of highlight details and loss of color saturation beneath the upper shoulder of the usual tone curve applied can’t be restored or better prevented adequately. Highlight details and colors which ARE in the Raw image are wasted."

I don't think Adobe has published details about the processing sequence of LR/ACR instructions when exporting an adjusted raw image to Photoshop, nor have they published the details of the algorithms which would allows one to be confident of this statement. I am also having trouble understanding exactly what this statement means: what do you mean by "usual tone curve applied"? What is it that can't be "restored or better prevented adequately? And where in the processing cycle are you thinking of: ACR or PS?

I also have trouble believing, based on my understanding and experience, how the Recovery tool can "waste" highlight detail and colors. Those always remain in the raw image. It is of course possible to overdo a Recovery Adjustment and emerge with overly dulled highlights, but stuff like that can happen with any wrongly applied procedure.
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Peter_DL

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« Reply #21 on: August 16, 2009, 03:17:16 am »

Quote from: MarkDS
DPL:

My understanding of the Recovery tool in LR/ACR is that it builds back detail by calculating replacement tones for blown primaries as long as at least one of the primaries is still present in the area to be "recovered".
Mark:

The problem is easy to see, but let’s support it by some numbers. Starting point is a "linear rendition", means all relevant controls zero in ACR, no curve applied. Then, Brightness & Contrast as well as Recovery are raised. The file was handled as Smart Object in Photoshop in order to have HSB readings (referring to ProPhoto RGB). Two sampling points were placed in the sky. It’s a sunset sky, but the channels are non-blown:

Linear rendition:
HSB(1)= 62°, 43%, 97%
HSB(2)= 44°, 45%, 91%

Brightness 50 & Contrast 25:
HSB(1)= 62°, 22%, 99%
HSB(2)= 43°, 27%, 98%

Brightness 50 & Contrast 25 and Recovery 50:
HSB(1)= 47°, 15%, 99%
HSB(2)= 41°, 24%, 90%

The S-curve which is de facto introduced by Brightness 50 & Contrast 25 leads to a drop of color saturation in the highlights, beneath the upper shoulder of the curve. It’s the typical behavior of RGB curves, even though the ACR implementation was reported to include a hue-lock. Once such damage of highlight colors is done, it can’t be undone in general and in particular not by the Recovery slider. It’s too late. Even worse, Recovery further reduces saturation and also twists the hue.

Alternatively, in Photoshop we could start with the "linear rendition" again and add a tone curve to be equipped with an inverted Luminosity mask, thus preventing this effect ab initio. Or, another option is to restore the information by means of "true recovery / HDR blending".

Many workarounds for something that could/should work in the Raw converter based on one single Raw file.

Peter

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JeffKohn

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questions about exposure blending from one file
« Reply #22 on: August 16, 2009, 09:22:56 am »

Quote
Fill light as well as the Recovery slider seem to be selection based.
I don't think they're selection based. Their effects are certainly non-linear across the tonal range; but as you use higher amounts the effect gets much broader. Slide the Recovery slider to 100% and it's pretty clear it's not just affecting the highlights.
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Mark D Segal

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questions about exposure blending from one file
« Reply #23 on: August 16, 2009, 10:38:10 am »

Quote from: DPL
Mark:

The problem is easy to see, but let’s support it by some numbers. Starting point is a "linear rendition", means all relevant controls zero in ACR, no curve applied. Then, Brightness & Contrast as well as Recovery are raised. The file was handled as Smart Object in Photoshop in order to have HSB readings (referring to ProPhoto RGB). Two sampling points were placed in the sky. It’s a sunset sky, but the channels are non-blown:

Linear rendition:
HSB(1)= 62°, 43%, 97%
HSB(2)= 44°, 45%, 91%

Brightness 50 & Contrast 25:
HSB(1)= 62°, 22%, 99%
HSB(2)= 43°, 27%, 98%

Brightness 50 & Contrast 25 and Recovery 50:
HSB(1)= 47°, 15%, 99%
HSB(2)= 41°, 24%, 90%

The S-curve which is de facto introduced by Brightness 50 & Contrast 25 leads to a drop of color saturation in the highlights, beneath the upper shoulder of the curve. It’s the typical behavior of RGB curves, even though the ACR implementation was reported to include a hue-lock. Once such damage of highlight colors is done, it can’t be undone in general and in particular not by the Recovery slider. It’s too late. Even worse, Recovery further reduces saturation and also twists the hue.

Alternatively, in Photoshop we could start with the "linear rendition" again and add a tone curve to be equipped with an inverted Luminosity mask, thus preventing this effect ab initio. Or, another option is to restore the information by means of "true recovery / HDR blending".

Many workarounds for something that could/should work in the Raw converter based on one single Raw file.

Peter

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Peter,

Reverting to your original points about the difficulties with Recovery, suppose you don't introduce an S-Curve with Brightness and Contrast (leave them at 0) and use Recovery in one iternation, no recovery in the other? It's not obvious that the demonstration you provide here proves your original points, or perhaps I'm a bit dense this morning.
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Mark D Segal (formerly MarkDS)
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Mark D Segal

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questions about exposure blending from one file
« Reply #24 on: August 16, 2009, 11:07:05 am »

Quote from: JeffKohn
Slide the Recovery slider to 100% and it's pretty clear it's not just affecting the highlights.

This is correct depending on how many tonal levels you include in "highlights", and most likely by design. I'm not sure exactly what is meant by "selection-based" in either your post or Peter's or whether it matters to the discussion. For any of these controls to work as intended, somehow or other they must be "selection-based" in the sense that they operate on select sets of tonal values in the image, with overlaps to provide for smooth tonal transitions between lighter and darker tones. So it seems to me that your observation quoted here means that as the Recovery is increased, the number of levels it impacts increases. This would correspond with one's observation of what occurs as we implement it. While there are other techniques in Photoshop which have different and perhaps stronger impacts in respect of revealing information from within the file, none of this would seem to support a contention that the Recovery function in LR/ACR has the kind of fatal negative effects being discussed in this thread.
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Guillermo Luijk

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questions about exposure blending from one file
« Reply #25 on: August 16, 2009, 11:23:52 am »

Quote from: JeffKohn
I don't think they're selection based. Their effects are certainly non-linear across the tonal range; but as you use higher amounts the effect gets much broader. Slide the Recovery slider to 100% and it's pretty clear it's not just affecting the highlights.
That is called a changing selection threshold  

Peter_DL

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« Reply #26 on: August 16, 2009, 11:23:53 am »

Quote from: JeffKohn
I don't think they're selection based. Their effects are certainly non-linear across the tonal range; but as you use higher amounts the effect gets much broader. Slide the Recovery slider to 100% and it's pretty clear it's not just affecting the highlights.
So when we reverse-engineer Fill Light or Recovery, every change per pixel can expressed by one single global equation? Let’s take something like a polygon approximation to cover complex functions including any non-linearity. I’ve yet to see this. Please show me.

Slightly philosophical: colors are 3D and so are blending operations. For reference, if we look at a Curve + inverted Luminosity mask, or the S/H tool in Photoshop, the basic three dimensions of freedom now are:
amount (strength) – opacity of blending.
tonal width – contrast of the mask.
and radius – blur applied on the mask.
Interestingly, it’s the Radius which definitively brings us out of the range of any A to B equation per pixel (as long as we don’t include an analysis of environmental pixel).

Assuming that Fill Light and Recovery are just (bundled to) one single slider, respectively, can not mean that the other parameter don’t exist. It’s just a lack of controls.

Peter

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« Reply #27 on: August 17, 2009, 03:40:46 am »

Quote from: MarkDS
Peter,

Reverting to your original points about the difficulties with Recovery, suppose you don't introduce an S-Curve with Brightness and Contrast (leave them at 0) and use Recovery in one iternation, no recovery in the other? It's not obvious that the demonstration you provide here proves your original points, or perhaps I'm a bit dense this morning.
To continue with above example, if we just raise Recovery while leaving Brightness and Contrast at zero, highlight saturation is reduced again compared to the initial "linear rendition". Also, note the hue twist which is more than 10° with the first measuring point.

Recovery 50:
HSB(1)= 48°, 33%, 94%
HSB(2)= 42°, 35%, 73%

Means, the approach to keep Brightness and Contrast low while raising Recovery + Exposure does not really help to preserve highlight color.

Mark, - at the end of the day there are many images, as far as I can tell, which profit from "HDR blending" from one single Raw file (see your own tutorial) and I’d still blame this to the insufficient mechanics of the Recovery slider. It’s both, a lack of controls (missing a Tonal Width slider) and the algorithm itself which does not preserve or restore the original color information.

Peter

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Mark D Segal

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« Reply #28 on: August 17, 2009, 10:07:26 am »

Peter,

The logic of the Recovery function suggests to me that one should NOT expect hue neutrality here, because it is building information for the missing (clipped) channels. Likewise for saturation, where the change you note is small in any case, and of course B should be reduced, as your measurement shows.

In my tutorial I used a combination of Recovery, Highlight adjustment in the LR Tone Curve and then further tweaking in PS. I do fully agree that luminosity blending in PS can produce value-added here, but I don't see how this somehow means there is something inherently wrong with the Recovery function in LR/ACR in respect of what it was designed to do.

Mark
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Marshallarts

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« Reply #29 on: August 19, 2009, 12:28:20 am »

I was just learning more about the Shadows/Highlights adjustment in Photoshop and it appears this has local control.

The manual states: "The Shadow/Highlight command does not simply lighten or darken an image; it lightens or darkens based on the surrounding pixels (local neighborhood) in the shadows or highlights. For this reason, there are separate controls of the shadows and the highlights."

For those who described their manual procedure to create HDR (for lack of better term) from one photo in Photoshop, did you know this adjustment tool existed!?
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Mark D Segal

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« Reply #30 on: August 19, 2009, 08:44:54 am »

Quote from: Marshallarts
For those who described their manual procedure to create HDR (for lack of better term) from one photo in Photoshop, did you know this adjustment tool existed!?

Yes, from the day it was put on the market.
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Mark D Segal (formerly MarkDS)
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Marshallarts

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« Reply #31 on: August 19, 2009, 12:56:15 pm »

Quote from: MarkDS
Yes, from the day it was put on the market.
Forgive my generalized question..  I'm sure you guys know the tool.  It was very briefly mentioned as S/H in a reply earlier in this thread.

But since this thread has spent so much time discussing either doing HDR fully manually in photoshop or automated in other HDR programs like Photomatix, I was puzzled why no one mentioned using the Shadow/Highlights adjustment perimeter in Photoshop.

I know Photoshop does automated merge to HDR which in my limited experience produces far worse images than Photomatix (though on the more realistic side the results IMO are still worse).  But it seems based on responses here and your own tutorial, Mark, that people don't generally use Photoshop's automated tool.  Of course the automated tool is for true bracketed exposure HDR and not the pseudo-HDR I began this thread about--however one still could process multiple exposures from one RAW file and use it as such.

But for true pseudo-HRD (from one image) I would love to hear how you feel about Photoshop's Shadows/Highlights tool since it does appear to do the local adjustments you all claim are necessary for good HDR-- and there are perimeters to fine tune it.

I sincerely want to understand this better.  I am a very confident shooter, it's what comes naturally to me.  I know exactly what I want and how to get it.  Now with digital processing I've finally realized I'm limiting myself as a photographer by not understanding these techniques.  However, the endless possibilities and countless ways to go about performing the exact same tasks (even within one program!), understanding the differences has been very frustrating, confusing, and ultimately has taken a big toll on my confidence.  I need to spend more time shooting and less learning all these things I never worried myself about before.  But there seems to be so many opinions and misdirection as to which way to go----I just want to know the right way to do it.

What is the downside of using the Shadows/Highlights tool (i.e. In discussing HDR and Photoshop, why hasn't anyone mentioned it being a useful tool if everyone knows about it?)
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Guillermo Luijk

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« Reply #32 on: August 19, 2009, 02:24:33 pm »

Quote from: Marshallarts
Now with digital processing I've finally realized I'm limiting myself as a photographer by not understanding these techniques.  However, the endless possibilities and countless ways to go about performing the exact same tasks (even within one program!), understanding the differences has been very frustrating, confusing, and ultimately has taken a big toll on my confidence.
----I just want to know the right way to do it.
I think it isn't worth getting frustrated for not understanding how a particular tool works, but just if it serves you well. After all they are black boxes that only the developers know exactly how operate. You are allowed to try them, master them looking at the results they produce, and use them if you feel they fit your needs. More and more tools and programs will always be, and there is not a right way to do things, there are many.

I will give you my approach in case it is useful to you. It's clear that to tone map the shadows and highlights of a high dynamic range scene we need to do local and global adjustments: global to fit the entire dynamic range of the original scene in a low dynamic range image, and local to enhance contrast locally so that images don't look dull.

To achieve that you can use black boxes (tools made by someone else that give you control through sliders):
- Photomatix
- Photoshop HDR Merge
- Photoshop Shadows/Highlights
- LR/ACR Shadow and Highlight recovery
...

and you can either use tools that allow you to see exactly what you are doing:
- Manual merging layers in PS with 2 different exposure RAW developments
- Local level adjustments with mask layers using the Levels/Curves tool
...

I chose the second option because even if it could _seem_ that some of the black boxes yield a good and quick result, you never know how it worked. So if one day they produce a bad result you will not know how to fix it.

In particular I start from a single neutral RAW development (MarkDS called that 'linear rendition'), and use curves with optional mask layers to lift the shadows while preserving the highlights. Don't need more that adjustment layers to go from the dull and underexposed original image to the final image without leaving PS:



You can download these 2 images with the appropiate layers from: capasauditorio.tif, capas2.tif. This is just my way, probably not the best, not the only one.

BR
« Last Edit: August 19, 2009, 02:27:18 pm by GLuijk »
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Marshallarts

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« Reply #33 on: August 19, 2009, 02:54:08 pm »

Quote from: GLuijk
This is just my way, probably not the best, not the only one.

BR
Thank you for your help!  Those samples are amazing.  Opening them in photoshop I see the layers and exactly what you did.  It really helps me understand the amount and kind of work you do to your images.  To be honest your skills are well beyond mine (as much as you humbly say "probably not the best"), and so I still have a long way to get to your level.  Maybe I'm in over-my-head seeking advanced level advice from experts with these questions, but I don't know where else to start---I want to learn these tools and techniques.  Do you recommend something that could get me up to speed with your level of understanding?

I am a little out of my league in what I'm trying to learn, but so often I find it's best to ask the pros and avoid learning bad habits.

I've been reading up about your Zero Noise program.  But I have a Mac and it seems all the programs you have are for PCs.  It looks amazing though!
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Guillermo Luijk

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« Reply #34 on: August 19, 2009, 03:56:06 pm »

Quote from: Marshallarts
Thank you for your help!  Those samples are amazing.  Opening them in photoshop I see the layers and exactly what you did.  It really helps me understand the amount and kind of work you do to your images.

As you can see I only use curves. Curves are a very powerful and flexible tool (in fact many of the 'black boxes' found on imaging programs are just hiding curves under their sliders) and I find them very intuitive, but for many people aren't. Consider them just another of the many possibilities to try.

I have no idea about English literature for image processing, but there must be a lot stuff. Perhaps someone here could recommend a good book oriented to teach film photographers about digital imaging, showing how they are to process their images to achieve the same things that previosly were done in the wet darkroom. That's why I wouldn't recommend a Photoshop manual, but a book specifically written for photographers.

Mark D Segal

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« Reply #35 on: August 19, 2009, 04:23:11 pm »

Quote from: GLuijk
Perhaps someone here could recommend a good book oriented to teach film photographers about digital imaging, showing how they are to process their images to achieve the same things that previosly were done in the wet darkroom. That's why I wouldn't recommend a Photoshop manual, but a book specifically written for photographers.

Yes, I would highly recommend two books: Ben Willmore's Photoshop Studio Techniques, and Katrin Eismann's Creative Digital Darkroom.
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Mark D Segal (formerly MarkDS)
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Mark D Segal

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« Reply #36 on: August 19, 2009, 04:32:47 pm »

Quote from: Marshallarts
Forgive my generalized question..  I'm sure you guys know the tool.  It was very briefly mentioned as S/H in a reply earlier in this thread.

But since this thread has spent so much time discussing either doing HDR fully manually in photoshop or automated in other HDR programs like Photomatix, I was puzzled why no one mentioned using the Shadow/Highlights adjustment perimeter in Photoshop.

I know Photoshop does automated merge to HDR which in my limited experience produces far worse images than Photomatix (though on the more realistic side the results IMO are still worse).  But it seems based on responses here and your own tutorial, Mark, that people don't generally use Photoshop's automated tool.  Of course the automated tool is for true bracketed exposure HDR and not the pseudo-HDR I began this thread about--however one still could process multiple exposures from one RAW file and use it as such.

But for true pseudo-HRD (from one image) I would love to hear how you feel about Photoshop's Shadows/Highlights tool since it does appear to do the local adjustments you all claim are necessary for good HDR-- and there are perimeters to fine tune it.

I sincerely want to understand this better.  I am a very confident shooter, it's what comes naturally to me.  I know exactly what I want and how to get it.  Now with digital processing I've finally realized I'm limiting myself as a photographer by not understanding these techniques.  However, the endless possibilities and countless ways to go about performing the exact same tasks (even within one program!), understanding the differences has been very frustrating, confusing, and ultimately has taken a big toll on my confidence.  I need to spend more time shooting and less learning all these things I never worried myself about before.  But there seems to be so many opinions and misdirection as to which way to go----I just want to know the right way to do it.

What is the downside of using the Shadows/Highlights tool (i.e. In discussing HDR and Photoshop, why hasn't anyone mentioned it being a useful tool if everyone knows about it?)

I almost never succeed in getting the effect I want out of Photoshop's Shadow/Highlight function, even with all the bells and whistles it comes with. It has a tendancy to turn tonal values into grey mush, and it seems less effective than good use of Curves and Blend Modes for extracting detail, increasing shadow detail and taming highlights, while maintaining good contrast in those areas at the same time. There are of course images on which it may suffice and work very well. This isn't a business where one size fits all, as you have most likely come to appreciate; so I would not dismiss S/H out of hand - like all these functions, it has its place, but for much of what I do I find it less satisfactory than other techniques.

Yes, you are right, there are endless possibilities and countless ways of achieving essentially the same objectives, all producing either similar or differing results by a little of a lot. Photoshop/ACR/LR are very deep programs. But this isn't a reason to be frustrated or to lose confidence. On the contrary, treat it as a challenge and a learning experience. No-one serious about using these applications ever stops learning.
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NikoJorj

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« Reply #37 on: August 26, 2009, 05:29:29 am »

Quote from: Marshallarts
I know LR can do curve adjustments, what do you mean by LR's brush do tone curve adjustments?
It's because in LR, tone curve adjustments are global. As said here, this can be less than adequate for some tasks involving a good deal of tone mapping.

I personally feel that the ability to apply locally, with the brush, a curve adjustment, even if it wouldn't have all the power of PS's blending mode, could already do much of a good job in these diffults cases we're talking about.

Quote
Also I'm having trouble understanding your last sentence.  "...one exposure at base ISA.."  Do you mean process the RAW file bringing down exposure for the sky?  and how would that effect shadows?  or do you mean simply take the photo originally at base ISO unless you're worried about bringing up the shadows?  Could you please explain that?  (I didn't think you're talking about blending an HDR because we're talking about one exposure)
When facing a high dynamic scene, I generally take one exposure exposed for the highlight (that's what Guillermo Luijk did in the two examples above, if I'm not mistaken).
With such an exposure, I don't need much Recovery as the HL are already where they should (or not far). That's important because recovery is a problematic task, often involving some kind of guessing from the processing algorithm - better not to need it, imho.
As the shadow are very dark (as in Guillermo's examples), I need to bring them up - for that task, I find that LR/ACR's Fill Light slider (combined with the Blacks slider to restore contrast) is already not that bad. Of course, the PS methods used by Guillermo are better (because saturation of shadows is better controlled among other things) but it needs quite a bit of time, compared to pulling 2 sliders in LR. Compromises...
I take the shot at base ISO (100ISO with my goodol'Rebel) to ensure that there is not too much noise in the shadows after bringing them up.
« Last Edit: August 26, 2009, 05:43:30 am by NikoJorj »
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Guillermo Luijk

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« Reply #38 on: August 26, 2009, 06:51:32 pm »

Quote from: NikoJorj
As the shadow are very dark (as in Guillermo's examples), I need to bring them up - for that task, I find that LR/ACR's Fill Light slider (combined with the Blacks slider to restore contrast) is already not that bad. Of course, the PS methods used by Guillermo are better (because saturation of shadows is better controlled among other things)

To lift the shadows, a straight curve like this applied in Normal RGB blending mode:



will always keep colour and saturation. This simple curve just scales the 3 RGB values of the deep shadows by some >1 factor. As long as the relative ratios between R, G and B are preserved, hue and saturation are preserved too since we are just changing exposure (this is true even when using non-linear gamma profiles, except sRGB for which it will be aproximate). That's why I find this simple curve magical and very adequate to lift the shadows after HDR blendings.

In the end of the shadows to be lifted it is recommended a toe towards (255,255) so that if some part gets too overexposed, we will never clip a channel avoiding any partial saturation. The effect of the toe is softly desaturating the highlights up to pure white, which is also a desired behaviour.

Typical values of the control points of the curve to achieve different +EV overexposures are:



Regards.
« Last Edit: August 27, 2009, 08:05:49 am by GLuijk »
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Mark D Segal

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« Reply #39 on: August 26, 2009, 08:25:23 pm »

Guillermo, what Blend Mode are you using here - is it "Normal" or "Luminosity", because with "Normal" Blend Mode in RGB for curve movements this large one would at least expect saturation shifts.
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