Pages: 1 ... 3 4 [5]   Go Down

Author Topic: Camera calibration using a neural network: questions  (Read 4360 times)

32BT

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 3095
    • Pictures
Re: Camera calibration using a neural network: questions
« Reply #80 on: June 10, 2019, 02:52:04 am »


For me it's clear that going beyond (16,16) NN's for Lab models and beyond (4,4) for XYZ models doesn't add, so it's just invoking: "overfitting, come to me". This makes sense looking at the DeltaE evolution we already saw, which was actually very insightful in finding out where to stop regarding NN complexity:

Regards

It's also interesting to mention perhaps that it takes at least 3 nodes to produce a perceptual curve, while it takes only 1 node to properly represent linear, despite a tanh activation curve. Which probably explains why XYZ performs so much better as far as complexity is concerned.

This entire exercise raises one additional question that might be useful as amendment: how does a one layer config perform?

And, for some future exercise, it would be interesting to know what happens if you could define a custom activation function.
Logged
Regards,
~ O ~
If you can stomach it: pictures

Jack Hogan

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 795
    • Hikes -more than strolls- with my dog
Re: Camera calibration using a neural network: questions
« Reply #81 on: June 11, 2019, 09:08:50 am »

Excellent job Guillermo, starting to make sense now.
Logged

Guillermo Luijk

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 1837
    • http://www.guillermoluijk.com
Re: Camera calibration using a neural network: questions
« Reply #82 on: June 16, 2019, 08:37:10 am »

Doing some infographics to decorate the story:



Regards

Jack Hogan

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 795
    • Hikes -more than strolls- with my dog
Re: Camera calibration using a neural network: questions
« Reply #83 on: June 20, 2019, 05:21:36 pm »

Nice!
Logged

Guillermo Luijk

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 1837
    • http://www.guillermoluijk.com
HR-1 SuperChroma
« Reply #84 on: July 03, 2019, 02:47:55 pm »

Hugo Rodríguez (the person who shared with me the capture and measurements over his IT8) is launching tomorrow a new calibration card intended for higher precision colour rendering. It hast nearly 1000 patches:



I'll suggest him to share a RAW file and set of measurements over it, so as over the IT8 with the same camera and shooting conditions. In this situation the IT8 would serve as a validation set to prevent overfitting so as to more correctly measure the delta E's.

Find a description here (Spanish):

https://www.hugorodriguez.com/blog/la-hr-1-superchroma/

Regards

DP

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 584
Re: HR-1 SuperChroma
« Reply #85 on: July 04, 2019, 09:56:38 am »

Hugo Rodríguez (the person who shared with me the capture and measurements over his IT8) is launching tomorrow a new calibration card intended for higher precision colour rendering. It hast nearly 1000 patches:
printed with inks consisting from like ~8 pigments at best - so what is the point in that many patches other than marketing to make money ? and it looks at least semi-gloss - the hell for most except few to shoot it properly... just asking what is the point ?
Logged

Jack Hogan

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 795
    • Hikes -more than strolls- with my dog
Re: Camera calibration using a neural network: questions
« Reply #86 on: July 04, 2019, 11:42:23 am »

Some truth to that.  Looks like it comes with a black gloss reference card to help hunt down reflections and flare.  It mentions a USB key with files and software.  I wonder what the capabilities of the software are and if it also comes with 'factory' spectral readings.
Logged

Guillermo Luijk

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 1837
    • http://www.guillermoluijk.com
Re: HR-1 SuperChroma
« Reply #87 on: July 04, 2019, 04:17:30 pm »

printed with inks consisting from like ~8 pigments at best - so what is the point in that many patches other than marketing to make money ? and it looks at least semi-gloss - the hell for most except few to shoot it properly... just asking what is the point ?
Quoting Hugo: "The HR-1 is printed in short batches using a last generation plotter with 12 pigments, over professional paper [Epson UltraChrome] suited for certified tests, glossy, of maximum quality and low content in optical bleach. This allows for the widest available gammut [wider than Adobe RGB and reaching ProPhoto RGB in some patches]. Not only that: also the longest duration, which is approximately 60 years (vs 22 of chemical copies, according to the Wilhelm Imaging Institute)".

I can confirm shooting these cards is a pain if you want to avoid any kind of reflections. I failed to shoot a glossy IT8 having to give up (even tried to surround the camera with a black sheet to prevent me from reflecting any light). I'd say you need studio stuff and abilities to do a proper shot.

Listening to other colour expert, he doesn't agree with glossy and saturated colour cards because of the difficulty in having a proper shot, so your point makes sense. However I'm mainly interested in the training and validation NN exercise. Camera colour calibration for me is in fact irrelevant, but to do a more complete and rigurous test I see a good opportunity here. With 1000 patches we can safely go to a more complex (3.5x) and hence precise NN, and use the IT8 set for validation.

Regards
« Last Edit: July 04, 2019, 04:28:11 pm by Guillermo Luijk »
Logged

hurodal

  • Newbie
  • *
  • Offline Offline
  • Posts: 46
    • My website
Re: Camera calibration using a neural network: questions
« Reply #88 on: July 04, 2019, 04:53:41 pm »

Hi all!

My name is Hugo Rodriguez and I'm the guy who helped Guillermo with IT8-WG captures and launched the new colour chart just today.
I was registered here since years ago but my english was very poor then and barely posted once.

I'll explain:

my new chart is aimed for professional use. It's not easy to shoot, due to it's glossy finish. That's because it focus on quality and precision, not on ease of use.
This means it's not for shooting outdoors with the chart in one hand and the camera in the other hand: it needs a careful reflection control, and this usually is better done in studio.
Anyway, it's not that hard to shoot; you just have to do some very particular things that doesn't require highly difficult procedures and the reflections will be all eliminated.
The chart comes also with lots of helpful patches around and inside the chart for controlling those reflections.

It's aimed to achieve the best precision out there, for highly requiring purposes: art reproduction, commercials, e-commerce, high quality LUTs...

I'll be publishing next week an english version of my webpage so you can all read it. Also I'm in talk with Kevin raber for a future article about camera profiling here.

The chart is printed with an Epson 7900. Having 12 inks doesn't really make a big difference in the whole gamut comparing with 8 or 10. In fact, I'd say that 95% of the gamut is done with the main 4. The rest are just to improve the smoothness of the highligths or some particular colors.

It's glossy; this is the only way to achieve highly saturated colors and wide dinamic range.

It has a glossy black card in the back to help removing any reflection. the procedure and some recommendations are carefully explained in the manual, step by step (in english, about 35-page long).

It comes with dual reference file: one without the perimetral patches for lightning control and central cross and the other with all them. Both will come in two versions: XYZ, Lab, LCH and Spectral data. Measured from averaging 5 charts.

Optionally is can come with custom read spectral data.

It comes also with free software for both Win & Mac for profiling (CoCa for PC, RoughProfiler for Mac). I'm in talk with Graeme and authors of these softwares to get the SuperChroma added to their software.

I hope I clarified the questions :-)

Best regards from Barcelona

Hugo
Logged
Hugo Rodriguez

Coloratti member | PhaseOne certified professional | BenQ Ambassador

32BT

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 3095
    • Pictures
Re: Camera calibration using a neural network: questions
« Reply #89 on: July 04, 2019, 05:12:11 pm »

Seems unnecessary emphasis on gamut. Just offer matte versions as well. The slight decrease in gamut is offset by the infinite increase in capture consistency & stability, and thereby accuracy.

The majority of this is used in linear matrix conversions. There is not much to be gained by providing wider gamut patches. The patches merely need to be reasonably distributed over a reasonable gamut where the capture device operates distinctly linear (i.e. not deep blacks for example).

Also, there may be merit in randomizing the chart somewhat.
Logged
Regards,
~ O ~
If you can stomach it: pictures

DP

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 584
Re: HR-1 SuperChroma
« Reply #90 on: July 05, 2019, 03:03:03 am »

with 12 pigments
that will be inks, not pigments  ;D ... now deduct all those "blacks"
Logged

DP

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 584
Re: Camera calibration using a neural network: questions
« Reply #91 on: July 05, 2019, 03:10:06 am »

The chart is printed with an Epson 7900. Having 12 inks doesn't really make a big difference in the whole gamut comparing with 8 or 10. In fact, I'd say that 95% of the gamut is done with the main 4. The rest are just to improve the smoothness of the highligths or some particular colors.

and pigment wise you are not better (probably worse) then X-Rite charts

It's glossy; this is the only way to achieve highly saturated colors and wide dinamic range.

wide dynamic range you can achieve using different exposures and creating synthetic target data with rawdigger if you are so inclined ...


It has a glossy black card in the back to help removing any reflection. the procedure and some recommendations are carefully explained in the manual, step by step (in english, about 35-page long).

is there a link (URL) to the manual ?

Logged

DP

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 584
Re: Camera calibration using a neural network: questions
« Reply #92 on: July 05, 2019, 03:15:45 am »

Some truth to that.  Looks like it comes with a black gloss reference card to help hunt down reflections and flare.  It mentions a USB key with files and software.  I wonder what the capabilities of the software are and if it also comes with 'factory' spectral readings.

it also has to come with matte grey for the flat fielding ... as for software - the author says "it comes also with free software for both Win & Mac for profiling (CoCa for PC, RoughProfiler for Mac)."... I'd take dcamprof over those ...
Logged

DP

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 584
Re: Camera calibration using a neural network: questions
« Reply #93 on: July 05, 2019, 03:31:21 am »

and once you have 4-5-6-7-8 pigments that's it... all that wide DR & making it glossy to achieve saturation is all snake oil... you have just so many different spectral reflectances ... now if you so inclined to sell snake oil - make it 2 charts: matte and glossy - rawdigger perfectly allows to combine synthetic data from several shots and you don't need to have all patches glossy  ;)
Logged

hurodal

  • Newbie
  • *
  • Offline Offline
  • Posts: 46
    • My website
Re: Camera calibration using a neural network: questions
« Reply #94 on: July 05, 2019, 06:34:32 am »

I believe wider gamut gives more precise profiles, and so my testing has proved me.
matte printing does indeed help avoiding problems with reflections, but worsens a lot the dynamic range and the dark tones, which are as important as the rest.

I've done hundreds of profiles from many different charts and the very best precision came from this one. I'm preparing an in-depth article explaining all that.

Seems unnecessary emphasis on gamut. Just offer matte versions as well. The slight decrease in gamut is offset by the infinite increase in capture consistency & stability, and thereby accuracy.

The majority of this is used in linear matrix conversions. There is not much to be gained by providing wider gamut patches. The patches merely need to be reasonably distributed over a reasonable gamut where the capture device operates distinctly linear (i.e. not deep blacks for example).

Also, there may be merit in randomizing the chart somewhat.
Logged
Hugo Rodriguez

Coloratti member | PhaseOne certified professional | BenQ Ambassador

hurodal

  • Newbie
  • *
  • Offline Offline
  • Posts: 46
    • My website
Re: Camera calibration using a neural network: questions
« Reply #95 on: July 05, 2019, 06:40:03 am »

and pigment wise you are not better (probably worse) then X-Rite charts
I am not 'better' that X-rite, and X-Rite is not better than mine. Better can be a product, not a person or a company. Well, in my case it's just me: a one person job.  :)

wide dynamic range you can achieve using different exposures and creating synthetic target data with rawdigger if you are so inclined ...

I don't want to mess with rawdigger, well my customers. Yes, it can help in builing synthetic raw blending exposures (though I've never tried that with that software) but the customer target my chart is aimed to isn't a scientific, but a professional photographer.

is there a link (URL) to the manual ?

Not yet. Probably it will only be released in printed version.
Logged
Hugo Rodriguez

Coloratti member | PhaseOne certified professional | BenQ Ambassador

hurodal

  • Newbie
  • *
  • Offline Offline
  • Posts: 46
    • My website
Re: Camera calibration using a neural network: questions
« Reply #96 on: July 05, 2019, 06:44:29 am »

it also has to come with matte grey for the flat fielding ... as for software - the author says "it comes also with free software for both Win & Mac for profiling (CoCa for PC, RoughProfiler for Mac)."... I'd take dcamprof over those ...

Regarding flat fielding, I'll recommend to use C1's LCC system.
Dcamprof is a command line software, and I've never seen any photographer in my entire life using a command-line software.
BTW: their site is down, isn't it?

https://www.ludd.ltu.se/~torger/dcamprof.html

Bear in mind that my chart is aimed to photographers, that will be able to build an excellent profile by themselves or with my help. They are not scientific or programmers. So they stick to Capture One or Adobe software all the time.
Logged
Hugo Rodriguez

Coloratti member | PhaseOne certified professional | BenQ Ambassador

hurodal

  • Newbie
  • *
  • Offline Offline
  • Posts: 46
    • My website
Re: Camera calibration using a neural network: questions
« Reply #97 on: July 05, 2019, 06:58:43 am »

and once you have 4-5-6-7-8 pigments that's it...

Same thing I said and think. The main gamut is achieved with the main 4 inks, the rest are for improving details here and there.

all that wide DR & making it glossy to achieve saturation is all snake oil... you have just so many different spectral reflectances ...

I find your sentence bold and a bit agressive to me. Given the thing that you have never seen one of these charts, tested it nor even got access to the reference file, how can you state that?

So many different spectral reflectances? If there are 4 main inks, there are just 4 spectral reflectances. Then there are many mixes.
How many different spectral reflec. does a CC classic have? 24? How many a CC SG? (answer: 140)

But, anyway, I didn't know that many different spectral reflectances suppose a problem for a photography that will be always take under high quality sources, with high CRI: Prophoto, Broncolor...

I really don't get the point. But I detect some refusal. And also poor understanding of what's my chart aimed to, although I've explained clearly: art reproduction, e-commerce...

now if you so inclined to sell snake oil - make it 2 charts: matte and glossy - rawdigger perfectly allows to combine synthetic data from several shots and you don't need to have all patches glossy  ;)
I don't sell snake oil, and I won't push my customers to buy and use a software that will make their work much more complicated, thus making them refusing my chart. Is that so hard to understand?
I repeat: it's aimed to photographers, not to scientifics or tech geeks.

Regards,

Hugo
Logged
Hugo Rodriguez

Coloratti member | PhaseOne certified professional | BenQ Ambassador

MauriceRR

  • Newbie
  • *
  • Offline Offline
  • Posts: 30
Re: Camera calibration using a neural network: questions
« Reply #98 on: July 05, 2019, 02:20:21 pm »

Why X-rite Gretag 24p is good ? Because all patchs are targetted for having interesting colors AND spectral data close to objects with the same color in réal life (skin, greenery, etc) to avoid metamerism.
Logged

hurodal

  • Newbie
  • *
  • Offline Offline
  • Posts: 46
    • My website
Re: Camera calibration using a neural network: questions
« Reply #99 on: July 05, 2019, 04:28:02 pm »

Why X-rite Gretag 24p is good ? Because all patchs are targetted for having interesting colors AND spectral data close to objects with the same color in réal life (skin, greenery, etc) to avoid metamerism.

The CC24 is a good chart indeed, but specially for checking results. Don't forget it was designed 43 years ago (!) for visual check with chemical photography.
Logged
Hugo Rodriguez

Coloratti member | PhaseOne certified professional | BenQ Ambassador
Pages: 1 ... 3 4 [5]   Go Up