Current Server Time: 03:04 (Central Europe)

#apertus IRC Channel Logs

2015/01/04

Timezone: UTC


01:09
davidak
joined the channel
01:28
troy_s
intracube: White point doesn't matter on a sensor as the filters are fixed.
01:29
danieel
troy_s: hi... that is a quite delayed answer :))
01:29
troy_s
It matters, of course, when mixing media or trying to deduce accurate colors after capture, but not in camera.
01:29
troy_s
danieel: Yeah. I am slow.
01:29
danieel
btw regarding white point... do you think it is enough to get 2 poitns and interpolate between them to cover others?
01:29
troy_s
danieel: TCP = Tin Cup Protocol
01:30
troy_s
danieel: Explain?
01:30
troy_s
I don't think I understand your query.
01:30
danieel
the normal approach (sorry for pulling dng here) is to define 2 wp calibration points. one for 3200 one for 5600 k...
01:30
danieel
anythign in between is a compromise/average
01:30
troy_s
Oh no.
01:30
intracube
troy_s: hmm, but for arguments sake, if you videoed a black/white photo with typical sensor
01:31
danieel
or one shall do every 100K calib matrix?
01:31
troy_s
danieel: Actual white point is a curve through CIE XYZ, so no.
01:31
intracube
if the colour temperature was very low, lik 1800k, then the RGB sensels wouldn't fill up evenly
01:31
intracube
in extreme cases you'd end up with more noise on blue channel
01:31
intracube
and some perceived resolution would be lost?
01:32
danieel
intracube: we had almost no blue on tungsten...
01:32
troy_s
danieel: The only correct method is to use CIE XYZ positions and adjust the channels in the LMS domain using Sharp, Bradford, or CIECAT02 etc.
01:32
intracube
danieel: what are you referring to?
01:32
danieel
that is high math again :) not up for that at this time of day
01:32
danieel
intracube: noise on blue
01:32
danieel
we got almost no blue...
01:32
troy_s
intracube: Except the sensor is agnostic, and the filling of the wells is balanced against the primaries and band capture of the filters
01:32
g3gg0
left the channel
01:33
intracube
right, but overcast daylight 6000K probably matches most sensors 'native' colour temp
01:33
troy_s
danieel: Not high math at all. Hell Bradford is a super simple matrix set. ;)
01:33
intracube
if there is such a thing?
01:33
troy_s
intracube: Nope. No such thing as white!
01:33
danieel
i can confirm that... the KAC is quite representative at skylight
01:33
troy_s
intracube: Hence my point, it is all arbitrary.
01:34
intracube
but what about filling the RGB sensels with equal voltage/charge?
01:34
troy_s
intracube: And the ability of the sensor to record levels is all hardware that ends up agnostic to the light
01:34
troy_s
intracube: doesn't matter
01:34
troy_s
intracube: Matters in imaging in post for sure
01:34
intracube
o.O
01:35
intracube
but there will be a point at which the RGB filters in the sensor treat as 'white'
01:35
intracube
and you'd get maximum dynamic range at that point?
01:35
troy_s
intracube: Nope
01:35
intracube
isn't sure what he's talking about at this hour
01:35
intracube
ok, I shut up now :)
01:36
troy_s
White doesn't exist nor does it matter at all if equi-channel is perceptually achromatic
01:36
troy_s
Where it _can_ matter is in post imaging where you need a neutral axis to cut through the space perfectly
01:37
troy_s
Elle wrote a decent article on that (wall o text sadly)
01:37
danieel
intracube: here is how it goes: sensor =1=1=1 what you mean by white is not really white, as there is a matrix coming on top of that, which leads to other RGB than equal
01:37
troy_s
Google "nine degrees well behaved color space"
01:37
troy_s
Exactly
01:38
troy_s
Think of the sensels as a map into 3D space
01:38
troy_s
No position in that entire space is magic
01:38
troy_s
Just as no position in CIE XYZ is neutral
01:38
danieel
oh, i have an idea... we should program the channel bot, that if somebody writes that white or black is a color, he/she should be kicked from the channel :)
01:38
troy_s
White (and black) do _not_ exist
01:39
troy_s
And only exist in the display referred domain
01:39
troy_s
Naw. It matters. Huge even. But we need to keep our scene referred and display referred subject to different evaluations.
01:40
troy_s
In manipulation of images, having R=G=B being achromatic is a much bigger deal
01:40
troy_s
In data representation and gathering or expression, no real deal.
01:40
danieel
yes - i have an algo for saturation, which depends on R=G=B being achromatic, otherwise it would not work
01:41
troy_s
intracube: Sense?
01:41
troy_s
intracube: Ask yourself, if you are sitting in a room, what is white?
01:41
danieel
tough question
01:42
troy_s
And the moment that becomes irrelevant is the moment you realize how a sensor works.
01:42
troy_s
Likewise, think about a massively intense color that perfectly matches the bands of say, the R filter in a sensel
01:43
intracube
troy_s: I meant white only as far as equal charge in each of the RGB channels
01:43
troy_s
It gets completely full, yet (theoretically only) doesn't fill the things beside it
01:43
danieel
so treating everything as a wavelength distribution curve is the best?
01:43
troy_s
intracube: Right. That isn't white :)
01:43
troy_s
danieel: Well it is just coordinates isn't it
01:44
danieel
i think the distribution curve is lot more than 3 scalars
01:44
troy_s
Just like a CIE xyY map
01:44
troy_s
Really just data
01:44
troy_s
We give it meaning
01:44
danieel
the 3 coordinates are rather the three integrals of the sensel sensitivity x original distribution curve
01:44
troy_s
And again, if we are careful in imaging, we align our work for manipulation to our colorspaces
01:45
troy_s
danieel: Sure. Math nerd.
01:46
troy_s
My point is really that our contexts determine what matters, and R=G=B=achromatic is truly something that is an issue in imaging and manipulation, not in the sensel world
01:46
troy_s
intracube: Remember too that _no_ sensor is narrow band
01:47
danieel
that is not the biggest issue
01:47
troy_s
So it is impossible for R=G=B=achromatic in a sensor
01:47
troy_s
(Ever)
01:47
danieel
i see the worst, that the peaks of the sensel filters do not match the primaries of common color spaces
01:47
troy_s
Doesn't mattee
01:47
troy_s
We map the sensor to our needs.
01:48
troy_s
Ideally via a 3D LUT of course
01:50
troy_s
(So nice to see pixel nerd talk here)
01:51
intracube
troy_s: sorry, it's too late for me to follow
01:51
danieel
i think the pixel nerd is one who paints its logos pixel by pixel :)
01:51
troy_s
intracube: Think on it tomorrow
01:52
troy_s
intracube: It really isn't nearly as complex as it seems. Just remember that the sensel is _not_ an RGB system really
01:53
troy_s
It has red, green, and blue filters, but how those filter is not a perfectly single band like a true RGB color space.
01:53
troy_s
And even more important, the raw data really has no clue what white or black is in our perceptual sense
01:53
troy_s
It is just an ignorant beast
01:54
danieel
i have a question
01:54
fsteinel_
joined the channel
01:54
troy_s
If we had three holes that we filled with a shovel of dirt while listening to music, hole 1 could get it on a and d, hole two on b,c,e, and hole three on fg
01:54
danieel
an ideal rgb space - shall be treated like a 3 narrow spikes? or as three gauss distributed curves (think of 3 phase AC current)
01:55
troy_s
You can see having equally filled holes really doesn't matter when capturing Moonlight Sonata over time
01:55
troy_s
Well almost but not quite as I understand it
01:56
troy_s
Wavelengths do not correlate to color, due to psycho physical magic
01:56
troy_s
But R / G / B shoot upwards and out in straight lines withing X / Y / Z, which is a bent nonorthogonal system
01:57
danieel
(yeah, i was fighting with my sister over what is red and pink-purple... i do cameras and she paints)
01:57
troy_s
(Bent to isolate Y as luminance)
01:58
troy_s
So RGB (in imaging perfect model terms, not sensels obviously) traverse through XYZ that hold their primary color vectors perfectly
01:58
danieel
i found my answer... the narrowness just increases saturation
01:58
fsteinel
left the channel
01:58
troy_s
?
01:58
danieel
having a more flat/distributed primary results in "faded" / reduced color space
01:59
danieel
narrow is more pure color
01:59
troy_s
Ah
01:59
troy_s
Yes makes sense
02:00
troy_s
Non-narrow would fill up two or three channels
02:00
troy_s
And be less saturated of course
02:00
troy_s
But it still isn't quite a perfect analogy because wavelengths aren't color
02:00
danieel
why?
02:01
danieel
they map pretty nicely
02:01
intracube
night all
02:01
danieel
night
02:02
troy_s
danieel: Because, as Fairchild says, color isn't physical
02:02
troy_s
It is psychological and physical
02:02
danieel
he was a person?
02:02
troy_s
Hence psychophysical
02:02
danieel
we call the company unfairchild these days... :)
02:03
troy_s
Fairchild is arguably one of the most well known color researchers out there currently
02:03
troy_s
Mark Fairchild. :)
02:03
troy_s
Developed CIECAM 02
02:03
troy_s
And led Munsell labs for a while etc
02:03
troy_s
Heavyweight color peep
02:03
danieel
I should move to US... so much is going on there
02:04
danieel
we have only the ICC guy in switzerland :)
02:04
troy_s
ICC
02:04
troy_s
Great stuff for printing, not great for photographic stuffs. :)
02:10
danieel
time to rest...
02:10
danieel
gn troy_s, nice talk
02:10
troy_s
Back at you
02:10
troy_s
Let's have more
06:54
Bertl
off to bed now ... have a good one everyone!
06:54
Bertl
changed nick to: Bertl_zZ
11:28
davidak
left the channel
12:44
ItsMeLenny
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13:00
g3gg0
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13:10
ItsMeLenny
left the channel
13:12
ItsMeLenny
joined the channel
14:03
se6astian|away
changed nick to: se6astian
14:22
lab-bot
sebastian created T244: image pipeline: highlight recovery. http://lab.apertus.org/T244
14:31
Bertl_zZ
changed nick to: Bertl
14:31
Bertl
morning folks!
14:36
se6astian
good morning!
14:40
ItsMeLenny
left the channel
16:17
ctag
left the channel
16:46
rhavan
left the channel
17:59
rhavan
joined the channel
19:31
jucar
left the channel
19:52
davidak
joined the channel
20:05
lab-bot
sebastian closed T71: invite all crowd funding backers to join axiom-community mailing list as "Wontfix". http://lab.apertus.org/T71
20:13
lab-bot
sebastian closed T171: add cheeseplate concepts to wiki as "Resolved". http://lab.apertus.org/T171
20:26
lab-bot
sebastian closed T219: Bluetooth as "Wontfix". http://lab.apertus.org/T219
21:16
Bertl
off for a nap ... bbl
21:16
Bertl
changed nick to: Bertl_zZ
21:17
aombk
joined the channel
21:20
davidak
left the channel
21:20
davidak
joined the channel
21:40
davidak
left the channel
21:49
aombk
left the channel
22:29
se6astian
good night
22:29
se6astian
changed nick to: se6astian|away
23:52
Bertl_zZ
changed nick to: Bertl
23:52
Bertl
back now ...