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#apertus IRC Channel Logs

2013/11/06

Timezone: UTC


02:35
[1]Sasha
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04:16
troy_s_
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05:15
Bertl
off to bed now ... have a good one everyone!
06:06
[1]Sasha
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07:48
PhilippeJ
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09:04
dmj_nova1
wow that meeting is early
09:23
Sasha_C
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10:41
PhilippeJ
Bertl, Hello !, I got a message form Gabe, he will send me what he curently has in term of dng conversion code (python script)
11:47
FergusL
cool ! could I see it ? if he's ok
12:19
Bertl
morning everyone!
12:19
Sasha_C
Morning Bertl
12:40
troy_s_
changed nick to: troy_s
12:42
troy_s
FergusL: Answering white balance... if you think of a device referred image as a volume of color points floating in space, the transform (either XYZ scaling, Von Kries, or Bradford) transforms the original point to the new point - stretching / bending the volume such that the values represent the color under the new white.
12:44
troy_s
FergusL: It isn't quite this simple when we get into the psychophysical domain as phenomenon happen. Lower luminance levels for example, hand off the color receptors to the monochromatic ones (so your eyes see less to no color at lower luminance) and
12:44
troy_s
FergusL: ...metamerism phenomenon where your brain makes up the color seen.
12:44
troy_s
etc.
12:45
PhilippeJ
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12:45
troy_s
eg FergusL - http://wiki.blender.org/index.php/File:Orange.gif
12:45
troy_s
Local contrast makes your brain interpret identical values differently
12:46
troy_s
(tied to how your brain interprets the scene)
12:47
Bertl
well, isn't that more like this one: http://www.businessballs.com/images/shadow-illusion.jpg
12:47
troy_s
and this http://wiki.blender.org/uploads/b/b2/Grey-cube-color-squares.jpg
12:47
troy_s
where the blue squares on left and yellow squares on right are actually achromatic values
12:48
troy_s
http://wiki.blender.org/uploads/thumb/2/2b/Grey-cube-squares.jpg/800px-Grey-cube-squares.jpg
12:48
troy_s
Bertl: Yes indeed. Different phenomenon however I believe
12:49
troy_s
Bertl: and culture influences perception as well (see Herskavits et al)
12:49
troy_s
I believe Mark Fairchild lists all the psychophysical phenomenon in his CIECAM02 paper.
12:53
Bertl
in the color squares, the funny part is that the yellow and blue squares are actually the _same_ gray :)
12:53
PhilippeJ
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13:00
FergusL
http://wiki.blender.org/index.php/User:Sobotka/Color_Management the cyan/green "confusion" is impressive there
13:03
troy_s
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13:04
troy_s
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13:05
FergusL
troy_s: "device referred image" == still bound to the limits of the device space ?
13:08
FergusL
I think I get it about white balance it's again a transform
13:58
troy_s
FergusL: Display / Device / Output referred - 0 to max (eg sRGB display)
13:59
troy_s
FergusL: Scene referred = 0 to theoretical infinity, linear relation.
13:59
FergusL
yes
14:00
FergusL
shall I think about white balance in an image as : One white reference point (moved around in XYZ with transforms) and all other values in the image relative to this reference ?
14:31
troy_s
FergusL: More or less a good summary from the data side.
14:32
troy_s
(and remember, not all transforms for white point are equal - Bradford etc.)
14:39
FergusL
troy_s: in what aren't they equal ? quality ? or simply the result ?
14:40
PhilippeJ
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14:55
troy_s
FergusL: 'quality' of the transform.
14:55
FergusL
ok
14:56
troy_s
Bertl: And to answer your earlier question: I believe profiling the sensor is a prudent choice to at least get a sense of the color gamut and latitude. I wouldn't publish the results, but it is important stuffs for a camera aimed at cinema crafting.
14:57
FergusL
why wouldn't you publish the results ?
14:57
troy_s
Bertl: The folks that have a hope of being interested in such a device will be deadly interested in the color gamut and latitude. (Namely director of photography archetypes.)
14:58
troy_s
FergusL: Because it is too early and likely not 100% optimal / controlled. It would be a great point of reference for development however.
14:58
Bertl
well, I don't think there is any reason to hide or hold back information in this regard
14:59
FergusL
troy_s: but releasing double checked info with the proper tool later is a good thing, right ? that's what I would do
14:59
Bertl
we are not producing/selling the sensor, and if we find out that this specific sensor is not suitable, we simply switch to a different one
14:59
FergusL
^ good to hear
14:59
troy_s
Bertl: I wouldn't suggest that either. Merely provide ample caveats and not offer an "official" publish of the results. A simple "additional information".
14:59
Bertl
and if somebody misinterprets development results as 'that's how the final image will look like' then they should stay away from development :)
15:00
troy_s
And exactly - it would be one more piece of information to see if the sensor is suitable for imaging.
15:00
Bertl
we are currently testing with a 'known broken' sensor :)
15:01
Bertl
still your 'answer' didn't really answer my question
15:01
Bertl
(which basically was: is it worth to do stills of the IT8 chart with known insufficient lighting)
15:03
Bertl
we will, for sure, make those images once the prototype is mobile and can be used by sebastian and friends for actual testing
15:04
troy_s
Bertl: I think a consistent tungsten image at a few white balance points (tickle registers for this?) would be a magnitude better than where it currently is.
15:05
Bertl
regarding publishing findings: I don't think there is any point for us to fund and build a camera which doesn't do what we want :)
15:06
Bertl
so if the sensor is insufficient or has bad color rendition, it helps to know that early, because we can save the time and spend it on something more productive
15:07
Sasha_C
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15:17
Bertl
off for now ... bbl
16:04
philippej
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16:16
se6astian
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16:18
philippej
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16:19
se6astian
good evening
16:23
FergusL
hello se6astian
16:38
philippej
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16:45
se6astian
I just sent the purchase order for the sensor to Cmosis
17:01
se6astian
I scheduled a team meeting for Monday the 11th at 12 PM GMT here on IRC, please join us at the time
17:02
se6astian
the association general assembly will start 2 hours later at 2PM
17:03
se6astian
sorry the meeting is at 12 AM GMT (noon)
17:03
philippej
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17:20
FergusL
se6astian: a working one for Bertl ?
17:23
se6astian
yes
18:01
rexbron
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18:02
rexbron
sup troy_s
18:06
rexbron
You guys got some coverage over on redshark
18:11
se6astian
hi rexbron, yes three articles in the last month :)
18:49
troy_s
rexbron: !
18:50
troy_s
Bertl: Exactly.
19:02
Bertl
back now ...
19:26
troy_s
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rexbron
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20:24
Bertl
off for a nap ... bbl
20:47
aombk
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21:31
aombk
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22:15
se6astian
time for bed
22:15
se6astian
goog night!
22:15
se6astian
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22:45
Sasha_C
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