Pages: 1 2 [3]   Go Down

Author Topic: Why do raw files require tone mapping to look perceptually correct?  (Read 951 times)

kpz

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 50
Re: Why do raw files require tone mapping to look perceptually correct?
« Reply #40 on: November 28, 2018, 01:07:26 PM »

Then I recommend you learn how to make import presets (and other presets) to produce an initial rendering you prefer as a starting point than looking at/asking about Capture 1 or any other product you presumably don't own nor know how to use.  ;)

Oh, I've done such things. It's just that Capture 1 has a month-long free demo, so there's no harm in trying it out and seeing whether it gives better initial renderings that I prefer as a starting point.
Logged

digitaldog

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 14710
    • http://www.digitaldog.net/
Re: Why do raw files require tone mapping to look perceptually correct?
« Reply #41 on: November 28, 2018, 01:11:06 PM »

Oh, I've done such things.
After writing this:

Why do raw files opened in Lightroom seem to almost always require massaging with the highlight and shadow sliders to look perceptually correct (that is, to reproduce what my eyes see in reality)?
If so, and you've found a preset that gives a better initial rendering you prefer as a starting point, my work is done here.  ;)
Logged
Andrew Rodney
Author “Color Management for Photographers"

BartvanderWolf

  • Sr. Member
  • ****
  • Online Online
  • Posts: 7271
Re: Why do raw files require tone mapping to look perceptually correct?
« Reply #42 on: November 28, 2018, 06:41:34 PM »

Thanks Bart.

While it may be entirely a personal artistic preference, as the Digital Dog notes, have you or others here noticed any other important "quirks" of the LR default rendering?

All Raw converters have specific benefits and drawbacks, it's the balance that counts. LR is more than a Raw converter, it's also part editor, and has some useful DAM functionality. How the specific strengths and weaknesses are appreciated, also depend on specific workflow requirements one might have. Personally, I don't like subscription software, which is why I stopped upgrading since version 5.7.1. I've been using it since version 1 first saw light.

For me, and my kind of workflow, I prefer Capture One Pro as Raw converter because the Raw conversion quality is better, with fewer demosaicing artifacts than LR. That may be due to its origin which had to deal with sensors without anti-aliasing filters and with fat pixels which tend to exacerbate aliasing artifacts. Its clipping recovery is not as good as LR's but C1 assumes that a (professional) photographer knows (which is not always the case) how to expose correctly, especially when in a controlled studio setting. Features like Lens Cast Correction (LCC), which also allows removing sensor dust, and Diffraction Correction, and very good color control, and Adjustment Layers, and tethering capability, are all very valuable to me, and real timesavers. I do prefer using the Linear Response Curve instead of the Film Response Curve setting, again to preserve better highlight separation.

Cheers,
Bart
« Last Edit: November 28, 2018, 06:54:53 PM by BartvanderWolf »
Logged
== If you do what you did, you'll get what you got. ==

kpz

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 50
Re: Why do raw files require tone mapping to look perceptually correct?
« Reply #43 on: November 29, 2018, 03:44:30 PM »

Indeed! And the possible and massive difference in the dynamic range of what we can see and what we can capture as so well illustrated in this must read:
http://www.lumita.com/site_media/work/whitepapers/files/pscs3_rendering_image.pdf

I finally got around to reading this paper. It is fantastic and answered virtually all of my questions. Thank you for posting it.

I do prefer using the Linear Response Curve instead of the Film Response Curve setting, again to preserve better highlight separation.

Cheers,
Bart

Do you know if Capture One "bakes in" any adjustments that cannot be removed? As pointed out earlier in the thread, "zero" on the ACR sliders is not actually "zero adjustment" in the more recent process versions. Some contrast, tone curve, and black point manipulation is being applied, and so on.

More precisely, suppose in Capture One that I set the tone curve to "scientific linear," the supplied camera profile is reasonably accurate, my monitor has been profiled, and I zero out all other sliders (e.g. sharpening). Then I take a shot of an X-Rite ColorChecker and process it in C1. Will the colors displayed on my screen by C1 be colorimetrically accurate to the physical ColorChecker (up to small errors in the profiling process)? (I would perform this experiment myself but I lack a ColorChecker -- with the questions I am asking it seems I should really get one...)

edit: I thought about this some more. We should ignore the bit about camera profiling for now since this can be fixed by a dedicated end user. The more pressing matter is the tone curve.

Consider "Blue Step Wedge example 1" in this link:
http://www.markshelley.co.uk/Astronomy/Processing/ACR_Critique/acr_critique.html

It shows conclusively that ACR/LR do not perform a linear tone curve, even in the early versions. So the real question is whether "scientific linear" properly renders the step wedge in C1. I am at work still but will try to perform this test later.
« Last Edit: November 29, 2018, 04:48:56 PM by kpz »
Logged

BartvanderWolf

  • Sr. Member
  • ****
  • Online Online
  • Posts: 7271
Re: Why do raw files require tone mapping to look perceptually correct?
« Reply #44 on: November 29, 2018, 06:16:19 PM »

Do you know if Capture One "bakes in" any adjustments that cannot be removed? As pointed out earlier in the thread, "zero" on the ACR sliders is not actually "zero adjustment" in the more recent process versions. Some contrast, tone curve, and black point manipulation is being applied, and so on.

I think all Raw converters do this to some extent. If one would use a truly linear Scientific profile, it would probably only be useful for reproductions under a specific light source. Capture One also offers two different Tone Curve Responses, one with a film-like shoulder roll-off in the highlights, and one that's more linear. I prefer the latter due to better highlight separation, and because the film roll-off pushes the brightness of optimally exposed Raw files into clipping (traditionally, PhaseOne cameras underexposed to preserve highlights).

Cheers,
Bart
Logged
== If you do what you did, you'll get what you got. ==

digitaldog

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 14710
    • http://www.digitaldog.net/
Re: Why do raw files require tone mapping to look perceptually correct?
« Reply #45 on: November 29, 2018, 06:39:13 PM »

Do you know if Capture One "bakes in" any adjustments that cannot be removed?
Nothing is 'baked in" that can't be removed per se. It is all read only, the raw remains raw. All converters produce an initial rendering just so you can see a full color image. And as we discussed, you can change this at any time.
Logged
Andrew Rodney
Author “Color Management for Photographers"

Chris Kern

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 679
    • Chris Kern's Eponymous Website
Re: Why do raw files require tone mapping to look perceptually correct?
« Reply #46 on: December 02, 2018, 05:35:52 PM »

So, more broadly, why do raw files require significant tone curving to look "right"? In Camera Neutral, for instance, they seem flat and lacking contrast. But again -- I should be seeing raw sensor data with basically just a gamma correction, and the sensor and I are seeing the same photons, so I expect roughly the same result.

I'm arriving late to this party, but it seems to me one point missing from the responses to date—I think Andrew implied it, but I don't believe he stated it explicitly—is that until you change the defaults, Lightroom is configured to display colors and tones in a normalized fashion that renders them similarly for all camera manufacturers and models.

Quote
“If you fell in love with the way your image looked when you chimped the LCD on the back of the camera, this first look in Lightroom or Camera Raw might be disappointing. Neither Lightroom nor Camera Raw uses the camera-maker’s software development kit (SDK) for rendering the digital negative, so expecting the preview to look like the camera LCD is unreasonable. When he was designing the rendering engine, Thomas Knoll made a conscious decision not to try to match the camera companies’ ‘looks,’ but instead to present you with a reasonable and normalized preview of your image.”

Jeff Schewe: The Digital Negative: Raw Image Processing in Lightroom, Camera Raw, and Photoshop, second edition

Whenever you select a different profile (in the Basic panel of the Development module), you get different colors and tones.  Adobe provides its own set of standard profiles (these are the normalized ones), some monochromatic and "artistic" variants that more radically alter the default renderings, and a set that attempts to imitate the JPEG processing options offered by each camera; these last camera-specific ones vary in quality, in my experience—based, I suspect, on (1) how much assistance the manufacturer provided to Adobe and (2) how much personal experience the Adobe software developers had with a particular camera.  The initial position of the sliders doesn't change when you select a different profile, so from the starting point provided by each profile you have the full range of adjustments.

With respect solely to the tone curve, Lightroom offers an Auto setting, again in the Basic panel of the Development module, that works surprisingly well for many images.  This feature recently was updated by using machine learning (presumably "neural-network" technology) to mimic the way experts in post-processing adjusted the tones in various samples of photographs.  Like the profiles, this can be used as-is, or as a starting point for further adjustments.  Unlike the profiles, this tool does alter the sliders, so you can see precisely what it has done to achieve the effect it produces.  When I'm having difficulty getting the global tones I want from a particular image, I find that the Auto tool's magic incantation sometimes helps me figure out where I've gone wrong.  (Of course, in many cases difficult images will become more tractable if you apply local in addition to global adjustments.)

Long story short, if you don't like the Adobe profiles, don't use them.  If you don't like how Adobe has profiled your particular camera(s), roll your own: there are plenty of online tutorials on how to do so.  But with a little practice, it's always possible to get where you want to be no matter where you start.

With respect to the intellectual exercise of understanding the precise semantics of the Adobe profiles, or how its development staff arrived at the settings for specific cameras, I guess you'd have to ask the Lightroom and Camera Raw developers.  Good luck with that.

Rand47

  • Sr. Member
  • ****
  • Online Online
  • Posts: 1401
Re: Why do raw files require tone mapping to look perceptually correct?
« Reply #47 on: December 08, 2018, 12:34:52 PM »

This has been a really good thread to follow along with.  Thanks to all who have contributed, and especially to Andrew for your expertise and the good resources. 

Good stuff ...

Rand
Logged
Rand Scott Adams
Pages: 1 2 [3]   Go Up