Luminous Landscape Forum

Raw & Post Processing, Printing => Adobe Lightroom Q&A => Topic started by: AndrewMcCormick on November 08, 2012, 12:23:15 PM

Title: Curves over sliders
Post by: AndrewMcCormick on November 08, 2012, 12:23:15 PM
In LR, can one technically be able to accomplish everything in the Basic WB and Tone with curves?
I just wonder if it's more efficient to learn how to control one curve more than up and down and all around with the sliders?
Title: Re: Curves over sliders
Post by: JeanMichel on November 08, 2012, 01:06:02 PM
Hi,
I find that the following the LR's team protocol of using the controls fin the order they are laid-out works best. I do however do go the the Lens Correction panel and pick my lens presets first; then back to the Basic panel. I really only use the Tone Curve to tweak Soft Proofs. Much of what I learned for how to best use LR I owe to the LR tutorials from here.
Jean-Michel
 
Title: Re: Curves over sliders
Post by: RFPhotography on November 08, 2012, 01:16:52 PM
The sliders in the Basic Panel and the curve in the Tone Curve panel do different things.  While you may be able to use one or the other and not both, the two aren't substitutes for each other.
Title: Re: Curves over sliders
Post by: Schewe on November 08, 2012, 01:25:37 PM
In LR, can one technically be able to accomplish everything in the Basic WB and Tone with curves?

No...the Basic panel of Process Version 2012 has image adaptive logic for highlight recovery and shadow boosting that can not be duplicated using curves. Curves as still useful but more for a precise finesse instead of trying to do the heavy lifting when tone mapping.
Title: Re: Curves over sliders
Post by: AndrewMcCormick on November 08, 2012, 02:14:25 PM
Thanks for the replies.  Just always looking for a faster and better way to work.

No...the Basic panel of Process Version 2012 has image adaptive logic for highlight recovery and shadow boosting that can not be duplicated using curves. Curves as still useful but more for a precise finesse instead of trying to do the heavy lifting when tone mapping.
That's exactly what I wanted to know.
Title: Re: Curves over sliders
Post by: jrsforums on November 08, 2012, 08:33:45 PM
The sliders in the Basic Panel and the curve in the Tone Curve panel do different things.  While you may be able to use one or the other and not both, the two aren't substitutes for each other.

By "not both", are you saying that the sliders and tone controls cannot be used on the same image?  If so, why?

....or am I misreading your statement?

John
Title: Re: Curves over sliders
Post by: aduke on November 08, 2012, 10:18:51 PM
There is nothing to stop you from using both. Generally, starting with the sliders, adding some curve if it seems to be useful, then, if necessary, adjusting the sliders again.

Jeff Schewe probably has more experience with all of this than anyone else on this board, go back  a few updates and re-read his.

Alan
Title: Re: Curves over sliders
Post by: jrsforums on November 08, 2012, 10:37:22 PM
I'd really like to hear Bob's reasoning.

John
Title: Re: Curves over sliders
Post by: aduke on November 08, 2012, 11:39:28 PM
I'm interested also.

Alan
Title: Re: Curves over sliders
Post by: stamper on November 09, 2012, 04:44:40 AM
Me too.
Title: Re: Curves over sliders
Post by: BartvanderWolf on November 09, 2012, 06:44:44 AM
By "not both", are you saying that the sliders and tone controls cannot be used on the same image?  If so, why?

....or am I misreading your statement?

Hi John,

It's most likely the latter. Bob probably intended to say you may not need to use both to come closer to a more desirable result, but they can have a markedly different effect on the image data.

The slider controls tweak not only the brighness level that their name suggests, but they adjust also local feature contrast and color in those regions while preserving edges (= adaptive tonemapping). The Curves control just changes the input versus output brighness levels which also changes color to a certain extent (because they are not strictly separated in an RGB colorspace).

Cheers,
Bart
Title: Re: Curves over sliders
Post by: Simon Garrett on November 09, 2012, 06:53:51 AM
Personally I find the new basic (tone) panel much easier to use than curves for most purposes - and much more powerful, too.  However, I still use curves occasionally, after I've done what I can with the basic panel. 

I've gone over quite a few pictures in PV2012 (LR4) which I'd previously processed in PV2010 (LR3) and used a custom curve of some sort.  In nearly every case I could get better results by resetting a linear curve, and using basic panel sliders - usually without any need for any curves adjustment. 
Title: Re: Curves over sliders
Post by: RFPhotography on November 09, 2012, 07:16:26 AM
By "not both", are you saying that the sliders and tone controls cannot be used on the same image?  If so, why?

John

No, that wasn't what I was saying.  Apologies for the confusion.  What I was saying was that you may be able to use either the Basic Panel sliders alone or the Tone Curve alone and that  you may not have to use both depending on the image and what you're trying to achieve.  That certainly doesn't preclude using both.  But the two controls do different things so one is not a substitute for the other. 

Bart, I thought the Tone Curve in LR/ACR was a true luminance curve and didn't impact colour.  Unlike the Curves tool in PS which, in Normal blend mode, does impact both contrast and colour which is why it's often changed to the Luminosity blend mode.
Title: Re: Curves over sliders
Post by: jrsforums on November 09, 2012, 07:25:12 AM
No, that wasn't what I was saying.  Apologies for the confusion.  What I was saying was that you may be able to use either the Basic Panel sliders alone or the Tone Curve alone and that  you may not have to use both depending on the image and what you're trying to achieve.  That certainly doesn't preclude using both.  But the two controls do different things so one is not a substitute for the other. 

That's is what I assumed, but wanted to check
Quote

Bart, I thought the Tone Curve in LR/ACR was a true luminance curve and didn't impact colour.  Unlike the Curves tool in PS which, in Normal blend mode, does impact both contrast and colour which is why it's often changed to the Luminosity blend mode.

If I remember it correctly, I had a conversation with Eric on this sometime back...requesting a "switch" to luminosity blending of the curves in LR.  He confirmed it did not have it.  I don't remember, without searching for the notes, if he said it might be a future consideration.  I would love it if it were added.

John
Title: Re: Curves over sliders
Post by: stamper on November 09, 2012, 08:06:52 AM
Charlie Cramer has a tutorial posted on the site expressly about this subject. It was about 3 months ago. Very informative.
Title: Re: Curves over sliders
Post by: RFPhotography on November 09, 2012, 08:07:06 AM
If I remember it correctly, I had a conversation with Eric on this sometime back...requesting a "switch" to luminosity blending of the curves in LR.  He confirmed it did not have it.  I don't remember, without searching for the notes, if he said it might be a future consideration.  I would love it if it were added.

John

Hmmm.  OK.  I thought it already was set up that way.  Guess not.  Agreed, it would be good.
Title: Re: Curves over sliders
Post by: jrsforums on November 09, 2012, 08:22:32 AM
Charlie Cramer has a tutorial posted on the site expressly about this subject. It was about 3 months ago. Very informative.

Do you have a link?  His site doesn't see to have an index.

Edit....nevermind...on LuLa....but (very) quick review does not seem to address saturation shift.
Title: Re: Curves over sliders
Post by: stamper on November 09, 2012, 08:33:13 AM
There is a post on here from a couple of days ago where the Digital Dog retells a story about Dan Margulis asking Thomas Knoll to implement a luminousity curve in ACR and he declined much to Dan's chagrin. This was a while back.
Title: Re: Curves over sliders
Post by: jrsforums on November 09, 2012, 08:41:34 AM
There is a post on here from a couple of days ago where the Digital Dog retells a story about Dan Margulis asking Thomas Knoll to implement a luminousity curve in ACR and he declined much to Dan's chagrin. This was a while back.

As I mentioned above, I would love it...as an on/off switch....I have yet to find an image where it was not fixed by a little negative saturation. 

It may not be scientifically or mathematically exactly the same as luminosity, but we are playing horseshoes here, aren't we?

John
Title: Re: Curves over sliders
Post by: BartvanderWolf on November 09, 2012, 10:41:10 AM
As I mentioned above, I would love it...as an on/off switch....I have yet to find an image where it was not fixed by a little negative saturation.  

It may not be scientifically or mathematically exactly the same as luminosity, but we are playing horseshoes here, aren't we?

Hi John,

I think one has too look further ahead. With the (certainly until recent) slowly developing HDR tonemapping functionality (32-b/ch TIFFs) things like the ICAM (http://en.wikipedia.org/wiki/ICAM_(Color_Appearance_Model)) (Color Appearance Model) are becoming more important than strictly colorimetric color. Such a CAM (e.g. CIECAM02 (http://en.wikipedia.org/wiki/CIECAM02)) allows to e.g avoid oversaturated shadow colors in a perceptually believable way, or tune saturation clipping and perceptually correct brightness changes.

That may also be one aspect of the lack of response to Dan Margulis' supposed question, who tried to push L* a*b* processing, which is far from neutral even when switching (back and forth) to an RGB colorspace.

Cheers,
Bart
Title: Re: Curves over sliders
Post by: jrsforums on November 09, 2012, 11:23:55 AM
Hi John,

I think one has too look further ahead. With the (certainly until recent) slowly developing HDR tonemapping functionality (32-b/ch TIFFs) things like the ICAM (http://en.wikipedia.org/wiki/ICAM_(Color_Appearance_Model)) (Color Appearance Model) are becoming more important than strictly colorimetric color. Such a CAM (e.g. CIECAM02 (http://en.wikipedia.org/wiki/CIECAM02)) allows to e.g avoid oversaturated shadow colors in a perceptually believable way, or tune saturation clipping and perceptually correct brightness changes.

That may also be one aspect of the lack of response to Dan Margulis' supposed question, who tried to push L* a*b* processing, which is far from neutral even when switching (back and forth) to an RGB colorspace.

Cheers,
Bart

As Ricky said to Lucy, "You got some 'splaining to do."

Can you put that in horsey, horsey, duckie, duckie animal book terms.....that is, a bit simpler or detailed out so some, such as I, can better understand?

John
Title: Re: Curves over sliders
Post by: digitaldog on November 09, 2012, 11:26:18 AM
There is a post on here from a couple of days ago where the Digital Dog retells a story about Dan Margulis asking Thomas Knoll to implement a luminousity curve in ACR and he declined much to Dan's chagrin. This was a while back.

Actually that was Jeff.
Title: Re: Curves over sliders
Post by: AndrewMcCormick on November 09, 2012, 11:45:17 AM
Charlie Cramer has a tutorial posted on the site expressly about this subject. It was about 3 months ago. Very informative.
Thanks.  Perfect article for what I was looking for.
Title: Re: Curves over sliders
Post by: BartvanderWolf on November 09, 2012, 11:45:41 AM
As Ricky said to Lucy, "You got some 'splaining to do."

Can you put that in horsey, horsey, duckie, duckie animal book terms.....that is, a bit simpler or detailed out so some, such as I, can better understand?

Hi John,

It's complex material, but perhaps a visual demonstration help to grasp the importance of perceptual color and brightness adjustments. I found a nice example here (http://scanline.ca/ciecam02/). Look at the examples under the "The surround effect" heading for the effect of local/surrounding brightness on perceived color/brightness.

Here (http://simon.tindemans.eu/tools/tonability) is another approach, but specifically addressing similar saturation issues.

Cliff Rames made a Photoshop plugin (https://sites.google.com/site/clifframes/ciecam02plugin) (32-bit Windows version only) which allows to explore the wonders of perceptual transforms on your own images.

Cheers,
Bart
Title: Re: Curves over sliders
Post by: Tim Lookingbill on November 09, 2012, 01:34:55 PM
Why is it when scientists get into the act of controlling and defining a creative endeavor as photography, they seem to create some of the most blandest images implementing their complicated methods?...

http://www.cis.rit.edu/fairchild/HDRPS/Scenes/CemeteryTree(2).html

http://www.cis.rit.edu/research/mcsl2/icam/hdr/ (Are those image samples meant to be a scene referred starting point or are they finished renderings?)

Thanks to this thread and Bart's links I now know what scene referred is suppose to look like. However, the definition I don't agree with or even see or understand how it was established and defined. Simon Tindeman's definition of equalizing color and removing the characterization of the camera doesn't make a lot of sense from a creative standpoint.

How would one know if the character of a camera has been removed and who defines how it is done and what it looks like? I remember reading his points he was making with the behavior of saturation tied to contrast/luminance edits (demo'ed in his "Tonability" image samples linked here) to Thomas Knoll years ago over at the Adobe Photoshop forums. I never knew he was going for a scene referred starting point. Interesting that he finally came up with an app to address it but I still see it as way too much work for what it's worth.

Color equalization of the entire image makes a lot of sense from a workflow efficiency POV, but it doesn't address what it does to the creative editing process which appears to make it look less efficient.

I use both curves and sliders to make an image "pop" or in more scientific terms...to "accurately" reproduce the spectral reflectance characteristic provided by any given illuminant on the elements in a scene in order to give it a 3D look as well as expand the dynamics in an attempt to counter the gamut/dynamic crushing look of a print (offset press) on output. Saturation (a spectral reflectance characteristic) requires a luminance boost in order to pull this off perceptually, NOT ACCURATELY.

This is what I refer to as Vibrance where Richness (saturation in darker tones) shouldn't have as much luminance increase comparatively.

The parametric curve I now find indispensable in broadening the effects of the "Clarity" slider without introducing the familiar goofy looking solarized effect. I find small increases of the Fill slider combined with gradual back and forth increases in the Contrast slider aids in adding a lot of definition in the shadows more so than a curve tweak. However, the Parametric Shadow curve maxed to the left set to 100 with the two left triangles slid far to the left often adds an extra depth to roll off into black point without posterization better than the Black Point slider.

The flat looking shadows shown in those RIT.EDU linked hdr images are not what I'm after.
Title: Re: Curves over sliders
Post by: RFPhotography on November 09, 2012, 03:00:21 PM
Quote
Simon Tindeman's definition of equalizing color and removing the characterization of the camera doesn't make a lot of sense from a creative standpoint.

But that's the point of Tindeman's workflow, isn't it?  Using a 'scene referred' intermediary image as the starting point and then doing the creative processing after that.  As far as how you would know if the particular colour character of the camera were removed, that would be the work of a custom camera profile, no?

I think it makes some sense.  Particularly if you're not a fan of what Adobe gives you as a starting point with it's built in render curve.  It goes even further than that in PV2012 with the image adaptive highlight protection.  I know how to back out the render curve using a custom camera profile made with the curve set to linear but not sure how to back out the new highlight protection. 

FWIW I'd probably disagree with Tindeman on one point and that's whether highlight recovery should be a part of the workflow to generate the scene referred image or whether that's a part of the creative side of the workflow. 
Title: Re: Curves over sliders
Post by: Tim Lookingbill on November 09, 2012, 09:18:20 PM
Quote
As far as how you would know if the particular colour character of the camera were removed, that would be the work of a custom camera profile, no?

That's sounds like it would work, but in practice with regards to improving workflow efficiency established with the intent of producing pleasing looking images, it doesn't consistently work. It helps a bit as long as the image isn't drastically changed as the viewer remembers the scene. Simon's flat, desaturated sample image he uses is not a desired starting point I'm interested in.

It's also disappointing to see he still uses sample images that don't represent typical shooting scenarios of most street/landscape photographers to demonstrate the advantages of scene referred processing/editing. I'ld like to see him start off with one of those HDR images like the "Cemetery Tree" only using a single properly exposed shot (which I've done a few that way shooting Raw and with better results) and see if you get consistent results from the less contrasty scene he used.

Why take 4 steps back in order to flat line an image as a way to establish some theoretical "scene referred" starting point. It just looks like more work than it's worth.

I actually applied a similar methodology with an Epson flatbed scanner in order to see all the available tonal differences that made up useable detail from shadows to highlights scanning negatives that Epson's Gamma curve driven under belly kept plugging up and blowing out.

I couldn't use a profiling target/software package at the time so instead used a colorful test image properly exposed to make the image generally flat and desaturated with its histogram end points pulled well back in order to give toe & shoulder room for the inevitable squash and stretch clipping behavior caused by tone mapping and restoring normal contrast. On some images this method allowed for a simple sigmoid or umbrella shaped curve to make it all look right but it still needed a lot of local contrast to bring out clarity.

It worked for some images but became a big PITA with others that had more or less contrast and brightness appearance caused by various lighting situations captured from scene to scene.

In the end it just became more work across a wide range of images than it was worth. The equation that's being left out of "scene referred" processing with regards to efficient workflows is that reality has to be characterized as well, not just the camera's response, for getting consistent results.

If the defaults give contrasted results that hide detail, it's a lot easier to choose a Linear tone curve and/or set Contrast slider to zero than to turn everything off as a new default one size fits all that makes one image workable and the rest a PITA to edit.
Title: Re: Curves over sliders
Post by: Tim Lookingbill on November 09, 2012, 09:26:43 PM
I tried to do a search on 'image adaptive highlight protection' I couldn't find the answer I was looking for.

Does the adaptive part of that term refer to the way our eyes view (adapt) to a given level of contrasted scene or does this refer to adapting a look to an image with regards to rendering? IOW is it an editing term or human visual system term?
Title: Re: Curves over sliders
Post by: RFPhotography on November 09, 2012, 11:26:42 PM
I think what you're talking about is just a different approach to a workflow.  We each develop an approach that works for us.

As I understand it, the adaptive part of the render curve in PV2012, as well as the sliders in the Basic Panel, is based on the actual data in the individual image.  So the highlight protection will be different for different images.  WRT the sliders, a 10 point change on one image will give a different result from a 10 point change on another image.
Title: Re: Curves over sliders
Post by: Tim Lookingbill on November 09, 2012, 11:42:25 PM
Thanks for the explanation, Bob.

I finally found Jeff Schewe's outline of it on a Adobe forum thread which ends up going quite in depth...

Quote
The individual controls in PV 2012 are image adaptive meaning the adjustment and range of the controls adapt to your image. By default, PV2012 retains much more highlight and shadow detail than PV2010. Fill Light and Clarity were the two image adaptive controls in PV2010 (not sure is Highlight Recovery was). But now all the tone mapping in PV2012 adjusts the controls to the image. So they are much more flexible–which is why it's so hard to try to convert from PV2010's non-adaptive controls to PV2012's adaptive controls. There's some addition info on the Lightroom Journal in this article; Magic or Local Laplacian Filters (note, it's pretty deep stuff).

From this thread...

http://forums.adobe.com/message/4313870

...and the gear head take on what's going on...

http://people.csail.mit.edu/sparis/publi/2011/siggraph/

Again I'm not too thrilled with the results seen in their sample images. I don't know what part of the science they're studying that influences those kind of results.
Title: Re: Curves over sliders
Post by: Tim Lookingbill on November 10, 2012, 12:00:12 AM
Ok, a correction.

This science document indicates I was too quick to judge the initial samples...

http://people.csail.mit.edu/sparis/publi/2011/siggraph/additional_results/tone_mapping_large/cadik-desk02.html

Click on any of the hi rez images and see how clean and lacking in noise the results they achieved. Amazing!
Title: Re: Curves over sliders
Post by: RFPhotography on November 10, 2012, 09:08:12 AM
But the images should be low in noise, right?  That's the goal of using HDR, to maximise SNR and thereby reduce noise.
Title: Re: Curves over sliders
Post by: BartvanderWolf on November 10, 2012, 09:26:01 AM
But the images should be low in noise, right?  That's the goal of using HDR, to maximise SNR and thereby reduce noise.

Exactly. That's what allows to do accurate technical measurements on the images for research purposes, and (more important for us photographers) to do some heavy lifting in tonemapping.

Here's (http://people.csail.mit.edu/sparis/publi/2011/siggraph/additional_results/tone_mapping_large/HancockKitchenInside.html) another challenging image, although it's obviously a technical demonstration because I would have tried to a) create a better EXR source image (reduce Chromatic aberrations and perhaps use a more glare resistant lens), and b) do a more pleasing color rendering (more in the lines of the attached conversion, tonemapped in SNS-HDR and downsampled in LR).

Cheers,
Bart
Title: Re: Curves over sliders
Post by: Peter_DL on November 10, 2012, 10:26:43 AM
FWIW I'd probably disagree with Tindeman on one point and that's whether highlight recovery should be a part of the workflow to generate the scene referred image or whether that's a part of the creative side of the workflow. 

Highlight recovery for scene reconstruction could be just referring to the recovery of clipped channels, that is when only one or two channels are clipped while the third one is intact
- as opposed to the highlight recovery often needed to undo the damage from a 'creative' tone curve such as the famous S-curve.  Tindeman's approach leaves the door open for spatially non-uniform tone mapping, for example to furnish the tone curve with an inverted luminosity mask in Photoshop, thus, overcoming the need to re-insert information from the scene-referred rendition again.

Peter

--
Title: Re: Curves over sliders
Post by: RFPhotography on November 10, 2012, 12:23:29 PM
It was really a rhetorical question, Bart.  I knew the answer.  ;)

Except you can't repair or recover a completely clipped channel in LR/ACR, Peter.  At least I'm not aware of how it can be done.  If a channel is clipped, it's gone and no amount of playing with sliders is going to bring it back. 
Title: Re: Curves over sliders
Post by: Tim Lookingbill on November 10, 2012, 01:15:25 PM
Bart, that looks perfect.

Just wondering if all that scientific coding demonstrated in the provided links is engineered into current versions of Lightroom/ACR.

What is SNS-HDR? Is it a stand alone app or Photoshop plug-in?
Title: Re: Curves over sliders
Post by: Schewe on November 10, 2012, 01:36:06 PM
Just wondering if all that scientific coding demonstrated in the provided links is engineered into current versions of Lightroom/ACR.

The research in the paper is the basis of Process Version 2012, yes...and note the original paper discussed HDR which was what the original research was directed to, the engineers adapted the algorithms to work with standard raw image data and while 32-bit processing (HDR) wasn't included for the original LR 4.0 and ACR 7.0 releases, it was added for LR 4.x and ACR 7.x.
Title: Re: Curves over sliders
Post by: Peter_DL on November 10, 2012, 01:44:11 PM
... you can't repair or recover a completely clipped channel in LR/ACR, Peter.  At least I'm not aware of how it can be done.  If a channel is clipped, it's gone and no amount of playing with sliders is going to bring it back.

DCRAW can (http://www.guillermoluijk.com/tutorial/dcraw/index_en.htm).

--
Title: Re: Curves over sliders
Post by: BartvanderWolf on November 10, 2012, 03:04:13 PM
Bart, that looks perfect.

Well, there are a lot of different ways of tonemapping possible. As long as the basic image data is of decent (S/N ratio) quality, creativity can take over without noise becoming a distracting issue.

Quote
Just wondering if all that scientific coding demonstrated in the provided links is engineered into current versions of Lightroom/ACR.

Yes, in some form or another. The Farbman et al. paper was mentioned at LR introduction time, if I'm not mistaken. EDIT: It looks like I remembered correctly (http://blogs.adobe.com/lightroomjournal/2012/02/magic-or-local-laplacian-filters.html) (it was referenced in the paper mentioned in the article).

Quote
What is SNS-HDR? Is it a stand alone app or Photoshop plug-in?

It's IMHO currently the best stand-alone HDR tonemapping application (Windows only, although it reportedly runs fine under Parallels and such on a Mac) for the more natural looking results. For those interested, here (http://www.sns-hdr.com/) is the website (select your preferred language at the top right).

Cheers,
Bart
Title: Re: Curves over sliders
Post by: RFPhotography on November 10, 2012, 07:01:03 PM
DCRAW can (http://www.guillermoluijk.com/tutorial/dcraw/index_en.htm).

--

Are you talking about the highlight recovery section of GL's article?  If so, then no it 's not truly recovering the blown channel(s).  It's recreating or replacing data from other information in the image.  This can be done in PS as well with saturation masks.  The fact remains that you cannot truly recover data from a blown channel because there is no data to recover.  And recreating or replacing isn't the same.
Title: Re: Curves over sliders
Post by: stamper on November 11, 2012, 05:31:39 AM
But the images should be low in noise, right?  That's the goal of using HDR, to maximise SNR and thereby reduce noise.

That is one consideration. The best description that I have read was by Harold Davis. I am paraphrasing him.

The goal is to combine two images that can be used as a background layer in Photoshop for further processing and the result is one that can't be processed well without the HDR being used and it shouldn't be obvious that it started off as HDR, as so many examples unfortunately do. In a nutshell the grunge look isn't or shouldn't be the final goal of HDR.
Title: Re: Curves over sliders
Post by: Peter_DL on November 11, 2012, 07:57:01 AM
Are you talking about the highlight recovery section of GL's article?  If so, then no it 's not truly recovering the blown channel(s).  It's recreating or replacing data from other information in the image.  This can be done in PS as well with saturation masks.  The fact remains that you cannot truly recover data from a blown channel because there is no data to recover.  And recreating or replacing isn't the same.

Aren't we getting into semantics, Bob.

You were wondering about "highlight recovery" which S. Tindeman (http://simon.tindemans.eu/essays/scenereferredworkflow) states as part of the processing steps to generate a scene-referred rendition, and I pointed to the use of the term to describe the repair of clipped channels (single channels, by emulating the surrounding colors), just the way G. Luijk (http://www.guillermoluijk.com/tutorial/dcraw/index_en.htm) uses the term and explains it in his DCRAW tutorial.

We may consider finding a different name while the missing information is not the Raw capture, however, said "highlight recovery" still fits to the idea of scene-reconstruction while the information was in the scene.

Notwithstanding the above there are (of course) Photoshop techniques which attempt to do the same, as a kind of late correction.  Aside from mentioned use of a Saturation mask for targeted adjustments (http://www.luminous-landscape.com/tutorials/restore-clipped.shtml), there is a quite cool technique called "The Impossible Retouch (http://www.dgrin.com/showthread.php?t=21648)" (second example on the skin tones of the two girls). Although it requires changing to Lab mode, which will certainly distract some fellows around here from adopting it.

Peter

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Title: Re: Curves over sliders
Post by: RFPhotography on November 12, 2012, 08:29:10 AM
That is one consideration. The best description that I have read was by Harold Davis. I am paraphrasing him.

The goal is to combine two images that can be used as a background layer in Photoshop for further processing and the result is one that can't be processed well without the HDR being used and it shouldn't be obvious that it started off as HDR, as so many examples unfortunately do. In a nutshell the grunge look isn't or shouldn't be the final goal of HDR.

I think that's a fairly limiting definition of what HDR is and I don't think injecting his personal opinion about the 'look' of the image is warranted for an accurate definition.

Quote
Aren't we getting into semantics, Bob

No, I don't really think so.  But it depends on how broad any one person is willing to make a definition, I suppose.
Title: Re: Curves over sliders
Post by: digitaldog on November 12, 2012, 11:51:00 AM
It may not be scientifically or mathematically exactly the same as luminosity, but we are playing horseshoes here, aren't we

Sure seems that way to me, after starting with post 1 here and moving on....

The raw is never affected so what you end up with is either ideal for you or maybe you need to use another converter. This idea of trying to get "scene referred" data out of a converter then use Photoshop or another converter seems to be a boat-load of work. I sure wish someone would post a raw file, some exact settings and procedures such that I could see that setting say ACR/LR one way to produce this "scene referred" TIFF and subsequent edits in Photoshop provide better/faster/cheaper results then just moving the sliders in the converter.

If we take the same raw file in ACR and another converter, and we set the two such that someone says they are both scene referred, do the two converters thus provide a visual and numeric match to each other?
Title: Re: Curves over sliders
Post by: stamper on November 13, 2012, 04:13:47 AM
Quote BobFisher.

I think that's a fairly limiting definition of what HDR is and I don't think injecting his personal opinion about the 'look' of the image is warranted for an accurate definition.

Unquote

Bob it is all about personal opinion. The vast majority of the opinions that I have read on here - and other sites - is that the grunge look isn't liked and it gives the process a bad reputation. The photographers who do use it properly tend to get ignored because as stated their use of it isn't obvious. What is your definition?
Title: Re: Curves over sliders
Post by: RFPhotography on November 13, 2012, 07:16:32 AM
It would depend on whether we're talking about a very technical definition or a looser one.

From a very technical standpoint - and speaking strictly with respect to photography - I'd say that HDR a process which combines two or more images made at different exposure settings in specialised software to create a 32 bit high dynamic range, intermediary image, in order to maximise signal to noise ratio across the brightness range of the image.

What you won't see in that definition is any mention of tonemapping or any other process to bring the file back to something useable because that useable image is no longer HDR.

In a less technical sense, and again speaking strictly with respect to photography, I'd say that HDR is the combination of two or more images made at different exposure settings with the purpose of creating a final image that has a broader range of brightness than the camera is capable of capturing in a single image and optimising the signal to noise ratio across the brightness range of the image.

Again, no mention of what that final image looks like.  Why?  Because that's an artistic choice.  I don't like the very overprocessed look much either, although I will use it to some degree depending on the subject matter.  But it artistic choices have nothing whatever to do with what an hdr image is or isn't.

Some would say that newer cameras like the D800 with its 'tested' 14+ stops of drange are also HDR.  I disagree with that position for a couple of reasons.  First, I think that inherent in the process is that you're capturing a wider range than the camera can capture 'normally'.  If you're working with a single exposure then I believe you're working with the 'normal' brightness range of the camera.  Second, if you're working with a single exposure you're not optimising SNR across the brightness range of the image.  You're still going to be dealing with greater evidence of noise in the shadows which will be made more visible if those areas are pushed around much at all.
Title: Re: Curves over sliders
Post by: stamper on November 13, 2012, 07:55:09 AM
Bob I don't see much difference between. The first is my quote and the second yours.

The goal is to combine two images that can be used as a background layer in Photoshop for further processing and the result is one that can't be processed well without the HDR being used.

and

I'd say that HDR is the combination of two or more images made at different exposure settings with the purpose of creating a final image that has a broader range of brightness than the camera is capable of capturing in a single image and optimising the signal to noise ratio across the brightness range of the image.


However over the years of reading about HDR - I have two books - I can't remember the noise issue being taken into account. Is this an issue that possibly concerns you and possibly not others? :)
Title: Re: Curves over sliders
Post by: RFPhotography on November 13, 2012, 08:17:19 AM
Well, you're being selective in your comparison.  The part you left out is the part where that other definition continues on to opine about the processing of the images and what one should or, rather, shouldn't do in generating the final result.  I'd also disagree with the idea that the goal is (always) a single background layer in Photoshop.  That, again, goes into the editing of the image.  But to that end, I'd suggest that creating a single background layer in PS is likely not the goal in a lot of cases.  Rather I think a lot of people would create the combined image via layers and masks so that each layer can then be edited separately as may be needed to optimise the final result.  Sorry, but I see large differences between the two.

As far as noise, look back earlier in this thread.  Bart and I both brought up the idea of maximising SNR with HDR.  Is noise an issue just for me?  I'd hardly think so.  Truth be told, I'm probably one of the more tolerant of image noise on this board.  Unless one is going for a specific 'look' then maximising SNR is the goal of pretty much any photograph.  It's the whole reason ETTR came into vogue.  HDR - whether the 32 bit form or the (manual or automated) blended image form - is, for all intents and purposes, an extreme form of ETTR. 

Title: Re: Curves over sliders
Post by: stamper on November 13, 2012, 08:51:18 AM
Quote

It's the whole reason ETTR came into vogue

Unquote

I think Michael's original article didn't emphasis the noise issue, only capturing as much information as possible?

Title: Re: Curves over sliders
Post by: RFPhotography on November 13, 2012, 08:59:07 AM
Quote

It's the whole reason ETTR came into vogue

Unquote

I think Michael's original article didn't emphasis the noise issue, only capturing as much information as possible?



That's the whole reason for doing it!  More information, more signal, less evidence of noise.
Title: Re: Curves over sliders
Post by: jrsforums on November 13, 2012, 10:08:49 AM
Quote

It's the whole reason ETTR came into vogue

Unquote

I think Michael's original article didn't emphasis the noise issue, only capturing as much information as possible?



I believe Michael was taken to task on this by some of the sensor technocrats.  I think he now supports the fact of improved SNR.
Title: Re: Curves over sliders
Post by: RFPhotography on November 13, 2012, 11:02:19 AM
I don't think that Michael not mentioning the benefit of reduced evidence of noise by using ETTR in his original, now 9 year old, article can be taken as a suggestion that he doesn't think it's important.  But I also don't think that's what he did.  Very clearly the headline on the article is "Maximizing S/N Ratio in Digital Photography" (http://www.luminous-landscape.com/tutorials/optimizing_exposure.shtml).  I don't see how that can be taken as anything but recognising the benefits of ETTR wrt reducing the evidence of noise.  He discusses this explicitly in the section of the article titled "The Lesson".  Further, in the section titled "A Test" he discusses what could/should be seen by close examination of shadow areas between a 'normal' exposure and an ETTR exposure. 

I'm just not sure how it's possible to read that article and not come to the conclusion that the benefit if ETTR is increasing the SNR and reducing the evidence of noise.
Title: Re: Curves over sliders
Post by: bjanes on November 13, 2012, 06:39:48 PM

It's the whole reason ETTR came into vogue

Unquote

I think Michael's original article didn't emphasis the noise issue, only capturing as much information as possible?


I believe Michael was taken to task on this by some of the sensor technocrats.  I think he now supports the fact of improved SNR.

Yes, I remember those discussions well. In the original article, Michael spent an inordinate amount of time discussing the number of levels in the brightest stop of a digital capture, and in the ensuing flame wars Michael's sidekicks (Schewe and Fraser) stressed the number of levels in the brightest f/stop of an exposure as a rationale for ETTR, suggesting that improved tonality would ensue from ETTR. This evoked a reasoned scientific response by Emil Martinic in his masterful treatise (http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/noise-p3.html#ETTR) on noise and dynamic range, where he specifically referred to Michael's article and pointed out that the number of levels has little to do with the rationale of ETTR but that the SNR is what is improved and the benefit in in the shadows more than the highlights.

That is all remote history (in terms of digital imaging) and by now I think that all agree on the SNR rationale. In any event, we owe Michael gratitude for introducing the concept of ETTR to many of us.

Regards,

Bill
Title: Re: Curves over sliders
Post by: jrsforums on November 13, 2012, 09:11:32 PM
Yes, I remember those discussions well. In the original article, Michael spent an inordinate amount of time discussing the number of levels in the brightest stop of a digital capture, and in the ensuing flame wars Michael's sidekicks (Schewe and Fraser) stressed the number of levels in the brightest f/stop of an exposure as a rationale for ETTR, suggesting that improved tonality would ensue from ETTR. This evoked a reasoned scientific response by Emil Martinic in his masterful treatise (http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/noise-p3.html#ETTR) on noise and dynamic range, where he specifically referred to Michael's article and pointed out that the number of levels has little to do with the rationale of ETTR but that the SNR is what is improved and the benefit in in the shadows more than the highlights.

That is all remote history (in terms of digital imaging) and by now I think that all agree on the SNR rationale. In any event, we owe Michael gratitude for introducing the concept of ETTR to many of us.

Regards,

Bill

Well said Bill. 

Michael realistically set us on the path of the digital (RAW) zone system, where the important tone is lightest significant tone.  This is exposed where it will just barely not clip, then let all the other tones fall where they will.....adjust to taste in the raw converter.

John
Title: Re: Curves over sliders
Post by: donbga on November 13, 2012, 09:19:05 PM
I do however do go the the Lens Correction panel and pick my lens presets first;
 

According to a well known LR guru one may wish to delay applying Lens Correction until the last step. When Lens Correction is turned on there is a heavy computational penalty each time the image is redrawn.

Best,

Donbga
Title: Re: Curves over sliders
Post by: RFPhotography on November 13, 2012, 10:20:24 PM
According to a well known LR guru one may wish to delay applying Lens Correction until the last step. When Lens Correction is turned on there is a heavy computational penalty each time the image is redrawn.

Best,

Donbga

Adobe designed the top down workflow in the Develop module for a reason.  It's the order that the steps are recommended to be completed.