Pages: 1 [2]   Go Down

Author Topic: LumaRiver Profile Designer - Gamut Compression question?  (Read 2022 times)

scyth

  • Sr. Member
  • ****
  • Online Online
  • Posts: 597
Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #20 on: June 08, 2017, 08:49:20 AM »

in the Green due to double the amount of area sensitive to this due to the bayer design of most sensors. 

the amount of "green" sensels does not increase the sensitivity to "green" light ... resolution in "greens" - yes, sensitivity - no... sensivity is purely how you filter the spectrum through CFA, so purely depends on the SSF curves
Logged

Alexey.Danilchenko

  • Full Member
  • ***
  • Offline Offline
  • Posts: 144
Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #21 on: June 08, 2017, 09:50:41 AM »

the amount of "green" sensels does not increase the sensitivity to "green" light ... resolution in "greens" - yes, sensitivity - no... sensivity is purely how you filter the spectrum through CFA, so purely depends on the SSF curves
Sensiitivity depends on silicon, microlenses and filters not just filters.
Logged

scyth

  • Sr. Member
  • ****
  • Online Online
  • Posts: 597
Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #22 on: June 08, 2017, 09:53:11 AM »

Sensiitivity depends on silicon, microlenses and filters not just filters.
of course... the use of "purely" above was just for rhetoric purposes  ;D
Logged

Ghibby

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 72
Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #23 on: June 08, 2017, 10:16:27 AM »

I understand that the sensitivity to green will not be altered but the ability to distinguish more subtle tonal transitions in Green will surely be better due to the higher number of sensels. Noise in the green channel is almost always lower than red or blue as well due to more surface area being dedicated to light / photon collection, another factor that will help with superior tonal transitions in the green channel
Logged

scyth

  • Sr. Member
  • ****
  • Online Online
  • Posts: 597
Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #24 on: June 08, 2017, 11:07:27 AM »

I understand that the sensitivity to green will not be altered but the ability to distinguish more subtle tonal transitions in Green will surely be better due to the higher number of sensels.

you have the same spectral sensivity = methameric failures (inability to distinguish certain "colors") will be the same ...

Logged

Tim Lookingbill

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2111
Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #25 on: June 08, 2017, 03:37:52 PM »

Just a reminder for those that think they are capturing real color and transferring exactly how it was recorded by the camera's sensor.

It is not.

Your image is being reconstructed by software on your computer from voltage variations recorded for each pixel on the sensor in the form of grayscale from black to white and turned into 1's & 0's after it goes through the camera's Analog to Digital converter. A/D converters do some extra noise filtering on some camera brands that offer high bit culling of crappy noise pixels vs usable detail.

If you don't like the color you see on your computer it's too late to blame the camera and its electronics because you will never be able to control electronic gain circuits for each pixel site.

Think of this lack of gain control behavior to you trying to hold a magnet next to a piece of metal several millimeters from each where the closer they get to each other the stronger the pull until WAM!, they stick together, an example of the behavior of electronics on a sensor which we call "clipping/gain".

Sensor and lens filters are applied to slow this behavior down on top of exposure settings. And you're expecting way too much from software to control this as well. I rest my case.
Logged

Tim Lookingbill

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2111
Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #26 on: June 08, 2017, 03:48:11 PM »

And I forgot to add, if you want to fix color artifacts demonstrated in this thread, try using the adjustment brush with some notch out adjusts on the point curve. I've done this to get rid of those weird halos of neon signage on top of a robust camera profile. I usually just rattle through a few  that gets me closer to what I want.

A camera profile is not an editor that fixes every color anomaly as a one size fits all fix for every odd ball shooting situation. Electricity can't be controlled that well.
Logged

daicehawk

  • Newbie
  • *
  • Offline Offline
  • Posts: 37
Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #27 on: June 08, 2017, 08:01:37 PM »

And I forgot to add, if you want to fix color artifacts demonstrated in this thread, try using the adjustment brush with some notch out adjusts on the point curve. I've done this to get rid of those weird halos of neon signage on top of a robust camera profile. I usually just rattle through a few  that gets me closer to what I want.

A camera profile is not an editor that fixes every color anomaly as a one size fits all fix for every odd ball shooting situation. Electricity can't be controlled that well.
[/quote
It is not electricity and magnets. It is just non-Luther-Ives spectral sensitivity of sensels and uncomparable to the human eye dynamic range whose limits are set for the whole frame unlike the local adaptation in the retina/brain.
   
Logged

Tim Lookingbill

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2111
Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #28 on: June 09, 2017, 01:10:51 AM »

Quote
It is not electricity and magnets. It is just non-Luther-Ives spectral sensitivity of sensels and uncomparable to the human eye dynamic range whose limits are set for the whole frame unlike the local adaptation in the retina/brain.

You misunderstood my point about electricity (electrons) and magnets. I was describing the rate of gain/clipping behavior of photon (electrons from light) charges on each pixel site with regard to capturing saturated colors as those shown by the OP's test image. Consumer grade digital cameras are not meant to be precise and consistently precise scientific instruments in capturing accurate color in all scenes especially those containing saturated colors whose saturation signal (affected by varying luminance levels) whose gain rate behavior is similar to my magnet/metal analogy.
Logged

sebbe

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 68
Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #29 on: June 09, 2017, 04:51:32 AM »

With the "Edit Look Adjustment" you can change any color(range) or relax parameters. Maybe you tried only on single colors instead of ranges? (Choose a different "Type" on top).
Did you tried something like this? I'm not sure if it works for your issue though, but it may be worth a try.

First two pictures shows the impact of the "look adjustments".
On the second two pictures you see a 100% crop of an indoor shot (whole pic upper right corner) with and without the "look adjustments". As you can see, I did the adjustments not for LEDs but for ugly cyan windows when I white balance indoor shots to thungsten lights.

Hi all,

This topic follows on nicely from the OP of this thread as it concerns colour gamut but in a high luminance / highlight clipped scenario.  I am very interested in LRPD and have been experimenting with it to deal with an issue that occasionally pops up in architectural photography scenarios with lots of LED lighting, especially with blue LEDís.  The issue as you can see below is how the camera profile deals with intense blue colours and detail rendition / retention when these are close to or beyond clipping.  My current method of dealing with the issue is by using a dual illuminate base profile I created in Adobe DNG profile editor. This was created with the colour checker passport and using a base profile of Camera Neutral with the standard Adobe ACR tone curve. The result is a profile very well suited to editing in LR or ACR as it is low in contrast, with good colour separations plus forgiving of highlight and shadow manipulation in high contrast images.  I feel the way the Adobe standard profile (and subsequent Adobe Standard V2 for the EOS 5Ds) is not ideal, over saturated colours and tonal transitions that are not subtle enough to my eyes. The Adobe cam neutral profile is more successful except for the hue shift of saturated blues into a more purple hue, my profile is a tweaked version of this.  When combined with a little adjustment of the blue lightness and hue sliders in the Calibration panel of Lightroom it is usually possible to get a very nice looking result that is perceptually close to the scene and resolves the blue to purple hue change quite successfully. I am not concerned in preserving faithful colour accuracy in these scenarios just a good looking rendering of the scene. 

I have applied a similar logic to creating a profile in LRPD and so far I am not even close to getting the results I want.  See attached images showing screen grabs of a test image that replicates a similar scenario from a Xmas decoration of blue LEDís.  The profiles uses are the labelled on the images clearly and as you can see the Adobe ones all seem to render a far more pleasing result in terms of detail retention and more significantly tonal transitions of colour, especially where it has clipped and then transitions into areas where only the blue channel clips.

I have also tried playing with the look adjustments panel and tweaking several colour patches but I can't seem to achieve a look I am happy with or one as smooth as the Adobe derived profiles.  Any suggestions on what is causing this behaviour and how it can be effectively dealt with? My suspicion is that the core issue is caused by the blue channel clipping and the red channel having barely any information, evident by high levels of noise in the red channel when you analyse such images carefully. The big question I have is whether LRPD can generate a profile that will give the nice smooth transitions of the Adobe Cam Neutral profile while avoiding the undesirable hue shift in the blue channel?


« Last Edit: June 09, 2017, 04:58:02 AM by sebbe »
Logged

daicehawk

  • Newbie
  • *
  • Offline Offline
  • Posts: 37
Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #30 on: June 09, 2017, 07:05:03 AM »

You misunderstood my point about electricity (electrons) and magnets. I was describing the rate of gain/clipping behavior of photon (electrons from light) charges on each pixel site with regard to capturing saturated colors as those shown by the OP's test image. Consumer grade digital cameras are not meant to be precise and consistently precise scientific instruments in capturing accurate color in all scenes especially those containing saturated colors whose saturation signal (affected by varying luminance levels) whose gain rate behavior is similar to my magnet/metal analogy.
It does not matter whether the camera is consumer-level or not. As long as the scene is captured without clipping on highlight specular reflection, then the saturated colors are not clipped too. The clipping and posterization in these cases is caused by development processes like profile\curves etc.
Logged

Tim Lookingbill

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2111
Re: LumaRiver Profile Designer - Gamut Compression question?
« Reply #31 on: June 09, 2017, 11:32:17 PM »

It does not matter whether the camera is consumer-level or not. As long as the scene is captured without clipping on highlight specular reflection, then the saturated colors are not clipped too. The clipping and posterization in these cases is caused by development processes like profile\curves etc.

What are profile curves doing? Correcting for luminance within each RGB channel that has blown out detail as in the OP's red color example while the rest of the scene looks correctly exposed. Why wouldn't a profile curve be able to fix that on a consistent basis after building a profile from a target?

The camera profile is suppose to be characterizing how the entire camera system records properly exposed scenes, but for some reason just can't anticipate saturated color detail from blowing out.

This points to the scene non-linearity (hot spots in mid-range saturated color detail) behavior I described with the gain rate behavior. Highlights are easy to anticipate with software because all channels are usually of equal luminance depending on the actual white balance of the scene. If the actual white balance of the scene is around 2800K instead of the established neutral D50 then those hot spot mid-range colors get really thrown out of proportion.

It doesn't explain why mid-range vibrant colors have their channels like green and red blow out as if they are acting as clipped highlights but don't show this clipping on a luminance only histogram.

I've attempted to shoot saturated orange flowers lit by the sun just above horizon and I have to under expose so much shooting Raw my camera's histogram highlight peak is in the middle. The point curve I had to come up with in Adobe Camera Raw no camera profile could build just from measuring a target.

The orange flower image came out perfect but not because of a camera profile. Something was bombarding that camera sensor to require I underexpose by half of my camera's dynamic range that a camera profile could not fix. What was it?
Logged
Pages: 1 [2]   Go Up