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#apertus IRC Channel Logs

2014/01/08

Timezone: UTC


00:00
Bertl
the alpha prototype was designed to allow full HD @ 25 FPS and maybe take 4k stills
00:01
danhanes
Makes sense - seems like pretty much the limit of the Zinq.
00:01
Bertl
we already have the 4k stills working perfectly as well as the HDMI output (although not of live images)
00:01
Bertl
the Zynq can do a lot more, but we are limited by the Zedboard peripherials
00:02
Bertl
i.e. the Zynq can easily handle 75FPS at 4k in the current setup (capture)
00:02
danhanes
Right - mixed terminology here :)
00:02
Bertl
and if done correctly, the 150FPS shouldn't be a problem either
00:02
Bertl
(at 12bit, full 4k that is)
00:03
Bertl
the problem is more the output, as the 7020 doesn't feature any multi gigabit tranceivers
00:03
danhanes
I believe you mentioned moving to the 7030 at one point
00:04
danhanes
Still capable of webpack development
00:04
Bertl
yes, it will be either 7015 or 7030 for the next step
00:05
danhanes
Once I feel competent to contribute some code - what area would is be most helpful for me to focus on ?
00:06
Bertl
depends on where we are at that point, I guess?
00:07
danhanes
right
00:16
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03:09
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03:17
Rambutan2000
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03:17
Rambutan2000
Morning all.
03:18
dmj_nova
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03:37
Bertl
morning Rambutan2000!
03:39
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04:13
Rambutan2000
I've been thinking about the design of the case and what features would be good bad. Since this project is open source do you guys think being able to 3d print and/or CNC parts of the case is important?
04:14
Rambutan2000
Hi Bertl!
04:20
Bertl
well, it might not be a primary goal atm, but I guess it would be nice to be able to fabricate certain parts yourself
04:23
Rambutan2000
Also has anyone been thinking into bus design for the expandable platform? I've seen open source IP cores for PCIe, but I've also been reading how USB 3.1 can reach 10gb/s
04:23
Rambutan2000
http://www.youtube.com/watch?v=isQ7cvuyoTw&feature=c4-overview-vl&list=PL1AFF5D9EB822C193
04:24
Bertl
USB is nice for interoperation, but as protocol, it is needlessly complicated
04:25
Bertl
e.g. to implement a serial console in USB 1.1 (not even 2.0) you need a lot of hardware and software, but you can achieve the same with almost no resources using rs232
04:25
Rambutan2000
yeah I tried reading through the 3.1 spec
04:26
Bertl
with higher data rates and newer versions the number of features increases, the hardware gets more expensive and protocols get more complicated
04:26
Bertl
and we definitely do not want a proprietary stack in our design
04:28
Rambutan2000
nope
04:54
Rambutan2000
Also what's the current thoughts on storage? SSD RAID?
05:00
Bertl
first step will be SDI with external recorder, i.e. no storage at all
05:00
Bertl
second step will be SSD raid on small SATA 6G SSDs
06:20
Bertl
off to bed now ... have a good one everyone!
06:39
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11:56
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12:41
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13:58
philippej
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14:05
Bertl
morning everyone!
14:06
philippej
Morning Bertl !
14:06
philippej
How goes?
14:07
Bertl
slow but steady ... and on your end?
14:07
philippej
Quiet and sleepy :-)
14:09
philippej
any news for image calibration ?
14:13
Bertl
well, actually we did some calibration tests yesterday and I have written a script to create a perfect IT8 chart based on the sensor data
14:13
Bertl
it just needs somebody to run it through the various tools
14:15
Bertl
http://vserver.13thfloor.at/Stuff/AXIOM/it8-tungsten-01-12ms-perfect.png
14:16
Bertl
I'm curious how that one will score with those tools
14:22
philippej
impressive, how have you made it?
14:23
Bertl
bash, gawk, imagemagick
14:23
philippej
:-)
14:24
S3bastian
joined the channel
14:24
S3bastian
hello!
14:25
philippej
Hello !
14:38
philippej
I have agryll runing, but I'm not 100% sure I know what I'm doing :-)
14:39
philippej
using your latest png, I get average error 5.664896 at the end of the chain
14:39
philippej
problem is that I used some random reference file and don't know if all the command line arguments are right
14:40
Bertl
which is quite interesting, as the chart itself is really perfect :)
14:40
philippej
don't you think it's the error of what the tool can achieve given those colors?
14:41
Bertl
I have no clue what the average error means (and I've posed the question several times without getting any answer)
14:41
guesst
what color space is the image ? :) (one should put that in filename for clarity)
14:42
philippej
here some info : http://comments.gmane.org/gmane.comp.graphics.argyllcms/5046
14:42
guesst
to me, the grays are not gray but yellow...
14:42
Bertl
which is kind of expected with tungsten sources
14:43
Bertl
note that this is not an idealistic chart, it is a perfect version of the actual sensor taking a picture of the chart
14:53
philippej
at least I get an icm file
14:54
philippej
I think the error % is based on what the tool managed to produce with the color it received
14:55
Bertl
we'll see what the calibration experts make from that chart
14:56
philippej
at least when I apply it to the png file in photoshop, I get an image that looks much more like a good chart
14:57
philippej
here : http://public.philippejadin.be/it8-tungsten-01-12ms-perfect-with%20profile%20applied.png
14:58
Bertl
yup, doesn't look completely wrong
14:59
philippej
but note I used a random reference file for IT8. I'd need the right reference file, for the precise batch used when printing the chart, as I understand it. Anyway, I guess experts will know better and faster :-)
14:59
Bertl
IMHO the chart was a little overexposed which shows in the bright areas
15:00
philippej
that's what those percentage of error mean
15:00
S3bastian
philippej: try this chart reference file: www.colorreference.de/targets/R100604.zip
15:01
philippej
S3bastian
15:01
philippej
doing right now
15:02
S3bastian
great
15:07
Bertl
S3bastian: btw, the chart image shows quite a number of speckles probably caused by dirt on the sensor
15:08
Bertl
(or maybe dirt on the chart? :)
15:08
S3bastian
good to know, I will clean the sensor and try to keep the new chart as clean as possible when it arrives
15:08
Bertl
10A, 12C, 16C, 19C foe example
15:09
Bertl
*for
15:09
S3bastian
in your chart script do you also compensate for FPN already?
15:09
Bertl
11H, 12F, 4F, 2L, 13H and so on and so forth
15:10
Bertl
no compensation so far, just statistics
15:11
philippej
weird result, probably caused by weird manipulations :-) http://public.philippejadin.be/it8-tungsten-01-12ms-perfect-with-profile-applied-bis-ok.jpg
15:13
Bertl
what I wonder is if the tools account for differences in brightness over the chart or if they simply assume it is evenly lit
15:13
S3bastian
do you think the grey "haze" from FPN could be an issue for the calibrations or will it not alter saturation levels?
15:14
Bertl
because the image I used has quite some differences between left and right (and also top to bottom but not so much there)
15:14
Bertl
i.e. it would be really beneficial to take a picture of the chart which fulfills the following requirements:
15:14
Bertl
- no reflections
15:14
Bertl
- even lighting (two light sources, one on each side)
15:15
Bertl
- no over or underexposure
15:15
Bertl
the actual angle doesn't matter much for this approach
15:16
Bertl
and of course, a number of images with the same setting would be nice to have to eliminate the dynamic noise pattern
15:20
gcolburn
joined the channel
15:23
Bertl
off for now ... bbl
15:27
philippej
Hi gcolburn
15:27
philippej
if you read the backlog, you'll find a very interesting file to play with, Herbert's corrected png :-)
15:32
gcolburn
hello
15:33
gcolburn
yeah I just ran it through Argyll
15:33
gcolburn
14.5% error unfortunately
15:33
philippej
is it bad?
15:33
S3bastian
I would like to understand what this error means exactly
15:34
philippej
latest try, profile applied, I cheated with the level feature to have stronger blacks : http://public.philippejadin.be/it8-tungsten-01-12ms-perfect-with-profile-applied-ter.jpg
15:34
gcolburn
I'll get you the best description I have found of it
15:34
dmj_nova
left the channel
15:34
gcolburn
I had one chart give me 12.5% yesterday
15:35
gcolburn
I embedded the matrix in the DNG, and compared the result with the previous matrix
15:35
gcolburn
the images were visually indistinguishable. and those were comparing new chart captures with older ones
15:35
S3bastian
is the error the "distance" from what the colors should look like to what they do look like after applying a LUT for RGB each?
15:35
gcolburn
"If the -v flag is used (verbose), then at the end of creating a profile, the maximum and average fit error of the input points to the resulting profile will be reported. This is a good guide as to whether things have gone smoothly in creating a profile. Depending on the type of device, and the consistency of the readings, average errors of 5 or less, and maximum errors of 15 or less would normally be expected. If errors are grossly higher than this, th
15:35
gcolburn
this is an indication that something is seriously wrong with the device measurement, or profile creation."
15:36
gcolburn
from the documentation
15:36
gcolburn
the canon shot you sent me before was was 3.x%
15:36
philippej
I got this : Profile check complete, peak err = 17.696363, avg err = 3.949152, is it so bad you think ?
15:37
gcolburn
that's using Argyll and a new chart?
15:37
gcolburn
from the CMV12000?
15:37
philippej
using this : http://vserver.13thfloor.at/Stuff/AXIOM/it8-tungsten-01-12ms-perfect.png
15:37
philippej
hrbert posted it an hour ago
15:37
gcolburn
that's the one I used :) except I have to convert to TIFF
15:38
philippej
me too
15:38
gcolburn
what commands are you using? I'll see if I can reproduce it
15:38
philippej
scanin -v it8-tungsten-01-12ms-perfect.tif It8.cht R100604.txt
15:38
philippej
(R100604.txt file from Sebastian)
15:39
gcolburn
yeah. we should have the same one downloaded from the website
15:39
philippej
colprof -v -D"Apertus axiom qm R" -qm -R it8-tungsten-01-12ms-perfect
15:39
gcolburn
that command isn't any different than mine, except I've sometimes turned on perspective compensation
15:40
gcolburn
okay. you're colprof command is slightly different
15:41
philippej
I removed -a(something) to use the default
15:41
gcolburn
I get that lower error
15:41
gcolburn
let me see the difference in our commands
15:41
philippej
and -R doesn't change a lot, except I suspect photoshop likes it better this way
15:42
philippej
I followed the tutorial, and am quite newbie in this, so take with a grain of salt :-)
15:42
gcolburn
yeah. I was using a command from another tutorial
15:42
gcolburn
for profiling
15:42
gcolburn
but yours gives better results :)
15:42
philippej
documentation here : http://www.argyllcms.com/doc/Scenarios.html#PS4
15:45
gcolburn
there's more matrix outputs in that command then I'm used to with different gammas
15:47
philippej
icm file here : http://public.philippejadin.be/it8-tungsten-01-12ms-perfect%20qm%20r.icm can be installed and applied in photoshop for example to test
15:47
gcolburn
I think you need -am. that tells it to create a matrix
15:47
gcolburn
instead of a LUT for example
15:48
philippej
then error level is much higer
15:49
philippej
Profile check complete, peak err = 44.376942, avg err = 14.835942
15:50
gcolburn
yeah. that's more like what I was getting
15:51
philippej
but without am it's visually better
15:51
gcolburn
I would think a LUT could handle a wider range of profiling than a matrix, but with less resolution
15:52
philippej
as they say about am
15:52
philippej
If profiling a camera in RAW mode, then there may be some advantage in creating a pure matrix only profile, in which it is assumed that the camera response is completely linear. This may reduce extrapolation artefacts.
15:52
philippej
but
15:52
philippej
is the sensor perfectly lilear?
15:53
philippej
an of the shelf camera in raw mode is probably, but since we are a step before...
15:54
gcolburn
from what I saw of Herberts tests its pretty linear
15:54
gcolburn
but might be worth reviewing again
15:55
philippej
if I open the different icm files in icc profile inspector, I see that the files without am have some curves
15:55
gcolburn
yeah
15:55
gcolburn
the embedded LUTs presumably
15:56
philippej
I guess
15:56
philippej
do you want a screenshot?
15:56
gcolburn
DNG has tags to embed a matrix for the raw converter to use
15:56
gcolburn
ICC profiles most often use a LUT
15:56
gcolburn
sure
15:58
philippej
http://public.philippejadin.be/curves.png
16:01
gcolburn
interesting
16:03
philippej
and there are also info for white and black point
16:03
philippej
the tool is here : http://www.color.org/profileinspector.xalter (windows only)
16:08
S3bastian
time to leave the office, I took 2 halogen tungsten softboxes with me and will create new chart captures tomorrow with them
16:08
S3bastian
see you
16:08
S3bastian
left the channel
16:10
philippej
see you !
16:45
philippej
left the channel
17:35
gcolburn
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18:19
gcolburn
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18:19
Bertl
wb gcolburn!
18:55
gcolburn
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19:32
se6astian
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19:40
Bertl
wb se6astian!
19:53
se6astian
thanks :)
19:54
se6astian
Jay replied, classic misunderstanding, good this is solved
19:56
Bertl
excellent
19:57
jucar
joined the channel
19:59
se6astian
and I took two tungsten softbox lights home from the university and took a day off tomorrow
20:00
se6astian
so I will shoot new charts tomorrow hopefully with fully uniform lighting and 100% accurate color temperature
20:00
Bertl
those are tungsten or halogen?
20:00
Bertl
because halogen != tungsten (lightwise)
20:04
se6astian
seems to be halogen
20:04
se6astian
http://www.bhphotovideo.com/c/product/285875-REG/Lowel_LC_95LBZ_Rifa_Lite_EX55_Softbox_Light.html
20:06
Bertl
okay, the spectrum is good on halogen AFAICT, but it has a different color
20:15
Bertl
btw, I created another perfect chart from my early daylight scene
20:15
Bertl
http://vserver.13thfloor.at/Stuff/AXIOM/scene_daylight_211ms_c2-perfect.png
20:15
Bertl
might be interesting to evaluate that one
20:17
se6astian
thank, I will try this one in Lprof now
20:22
se6astian
Average dE :
20:22
se6astian
11.09
20:22
se6astian
Standard deviation :
20:22
se6astian
8.35
20:22
se6astian
Peak :
20:22
se6astian
57.23
20:22
se6astian
Min :
20:22
se6astian
0.80
20:22
se6astian
Average Target error: (99% confidence)
20:22
se6astian
the brighter chart had an average dE (I guess this is the error) of around 6
20:22
se6astian
so as troy suggested slightly overexposed images seem to be better for profiling
20:24
Bertl
and average dE means?
20:24
se6astian
"deviation error" I guess, trying to find references on the net atm
20:25
Bertl
I think it is essential to put not just a name to those values but also a unit and an explanation what is actually measured
20:25
Bertl
otherwise it is just random numbers with a hope that smaller means better
20:26
Bertl
for example, the std deviation, 8.35, what deviates from what here?
20:26
Bertl
for sure, the colors within each tile do not deviate at all
20:26
se6astian
dE is short for delta E which is a standard way to measure color errors.
20:26
se6astian
http://lprof.sourceforge.net/help/checker.html
20:27
Bertl
what does peak 57.23 mean? what does peak here, where and why?
20:28
Bertl
and who is writing such a help with so many typose/grammatic errors :)
20:28
Bertl
shows how close the the color will be once the profile is applies
20:30
Bertl
so dE of 11.09 basically means (when the decibel part is correct) that the color is off by a factor of 10 or more?
20:31
se6astian
lprof profile inspection tab is very interesting
20:31
se6astian
it shows each color seperately
20:31
se6astian
what the color should be, what it was
20:31
se6astian
error in hue, chroma, luma
20:32
Bertl
so the error is in comparison to a perfect chart then?
20:32
Bertl
i.e. difference of each color to the assumed chart color?
20:32
se6astian
could be, not entirely sure yet
20:32
se6astian
would not make much sense tbh though
20:33
Bertl
if so, we will never get a lower dE, on the contrary, it will always be wrong
20:33
Bertl
but that would explain why the DSLR scores way better
20:34
Bertl
i.e. their 'raw' image will already be post processed regarding color calibration, at least to some degree
20:34
se6astian
This report shows how close the color will be once the profile is applied to the image.
20:34
se6astian
so it does take the created profile into account
20:35
Bertl
okay, so why is it off by a factor of 10 ?
20:35
Bertl
and where is it off by a factor of 10?
20:40
se6astian
good questions, no idea :)
20:42
Bertl
btw, I'm sure there is a list of color values used for the original chart
20:42
Bertl
it would be trivial to create a chart with those color values if you can put them in a list
20:43
se6astian
sure, but what would we do with that list?
20:50
se6astian
off to tv :)
20:58
Bertl
create a perfect chart and check what the various tools produce?
21:01
gcolburn
joined the channel
21:04
Bertl
wb gcolburn!
21:04
gcolburn
hello!
21:05
Bertl
http://vserver.13thfloor.at/Stuff/AXIOM/scene_daylight_211ms_c2-perfect.png
21:06
gcolburn
ah daylight
21:07
gcolburn
not sure if you saw this conversation earlier, but when philippej ran Argyll using a LUT instead of a matrix he had errors less that 4%
21:07
gcolburn
I was able to reproduce it
21:08
gcolburn
I've sort of wondered myself when you run into limitations of a 3x3 matrix⦠but most literature I read indicates a matrix is best for a camera profile
21:10
Bertl
well, we can do both as you know :)
21:11
Bertl
or to be precise, we are somewhere in between a 3D lut and a matrix
21:11
gcolburn
yeah
21:11
gcolburn
I got 14% error with that one
21:11
Bertl
do we already know what that means?
21:12
gcolburn
"If the -v flag is used (verbose), then at the end of creating a profile, the maximum and average fit error of the input points to the resulting profile will be reported. This is a good guide as to whether things have gone smoothly in creating a profile. Depending on the type of device, and the consistency of the readings, average errors of 5 or less, and maximum errors of 15 or less would normally be expected. If errors are grossly higher than this, th
21:12
gcolburn
this is an indication that something is seriously wrong with the device measurement, or profile creation."
21:12
gcolburn
that's all the documentation states
21:13
Bertl
okay, so it basically calculates how good the transformed image matches the expected
21:13
gcolburn
yeah, basically what I figured it did
21:13
Bertl
and the value you are stating is the maximum error?
21:13
Bertl
or the average?
21:13
gcolburn
average
21:13
Bertl
what's the maximum?
21:14
gcolburn
47%
21:14
Bertl
well, that is excessive
21:14
gcolburn
haha. yeah
21:14
gcolburn
but as I've said I haven't seen a visual difference between 12% and 20%
21:14
Bertl
can you tell which color causes this and is that for matrix or lut setup?
21:14
gcolburn
phillippej said that when he used the icc profile that was LUT based it looked better to him
21:15
gcolburn
I've been always testing matrix, except when I tried to reproduce the low errors with a LUT
21:15
gcolburn
if we wanted to switch to the LUT, we'd have to learn about the many LUTs that get embedded in the ICC profile and how to extract/use them
21:15
Bertl
okay, do we know what format the calibration files are?
21:15
gcolburn
they are icc profiles
21:15
Bertl
i.e. the ones which come with the chart
21:15
gcolburn
oh
21:16
Bertl
do you use them?
21:16
Bertl
or does it try to fit to an ideal chart?
21:16
gcolburn
there are 3 components
21:17
gcolburn
1) Your image
21:17
gcolburn
2) it8.cht which contains the edges I believe and the "ideal" values of each patch
21:17
gcolburn
e.g. the reference chart
21:18
Bertl
okay, can you point me to that file and do you know the format?
21:18
gcolburn
3) the measurements of the individual chart that we have (R100604.txt)
21:18
gcolburn
its all ascii
21:18
Bertl
good
21:18
gcolburn
very human readable
21:18
Bertl
not so good :)
21:19
Bertl
the .cht is part of the argyll package, yes?
21:20
gcolburn
first you run "scan in". it recognizes the patches in your image and determines the values in your image. this outputs a .ti3 file (human readable with the results), then you run "colprof" which will try to fit the data with a matrix or LUT and create an ICC profile
21:20
gcolburn
yes
21:20
gcolburn
comes with argyll
21:21
gcolburn
in the .ti3 file there are XYZ, RGB mean values for each patch, and a standard deviation
21:21
gcolburn
so you can see which patches it had more variance in
21:21
Bertl
hmm, first question regarding it8.cht
21:22
Bertl
it says 290 boxes, 288 I can explain (12*22 + 24) what are the two missing ones?
21:22
gcolburn
not sure
21:23
Bertl
hmm, maybe boxes does not necessary mean color areas
21:23
Bertl
it looks like the color values are only 288
21:24
gcolburn
ok
21:24
gcolburn
when you run scan in you can pass it options to draw on various parts of the chart it detected and dump a diagnostic image
21:25
gcolburn
here's a semi-theoretical question. how good is 9 degrees of freedom for characterizing the response of an RGB sensor?
21:26
gcolburn
with a LUT, you have more degrees of freedom in principle
21:26
gcolburn
DNG uses a matrix
21:29
Bertl
LAB is basically XYZ just with different coordinate system, yes?
21:31
gcolburn
LAB is designed to be more perceptually uniform than XYZ. but it is a transform to go between the two
21:31
gcolburn
slightly more complicated than just a matrix transform
21:31
gcolburn
DNG requiries XYZ
21:31
gcolburn
but, we are not limited to that for the HDMI LUT implementation
21:32
gcolburn
in the LUT code I uploaded I go from camera to sRGB in one step, by combining the camera to XYZ and XYZ to sRGB transforms in one matrix (plus gamma encoding at the end)
21:32
Bertl
just looking at the R100604.txt and trying to make heads or tails out of it
21:34
Bertl
can we remove the R100604.txt easily from the equation?
21:36
Bertl
i.e. can we pretend that our IT8 chart is a perfect replica of the ideal chart?
21:36
gcolburn
well IT8 charts can be made for different purposes. I believe the R100604.txt is needed for Argyll to understand what to expect from the chart based on the photometric readings that Faust did on the chart
21:36
gcolburn
not sure
21:36
gcolburn
I think the issue is that you can't manufacture a perfect chart
21:36
gcolburn
and capture
21:36
Bertl
of course, I'm just asking because I would like to do some tests
21:37
Bertl
and eliminating the R100604.txt from the equation simplifies things
21:37
gcolburn
well there's nothing stopping us from trying our own calibration techniques
21:37
Bertl
the question now basically is, can we drop the R100604.txt or do we need to replace it by a dummy
21:38
gcolburn
we should read up on two things. 1) how the R100604.txt was created
21:38
gcolburn
2) how scan in uses it
21:38
gcolburn
http://www.argyllcms.com/doc/scanin.html
21:38
Bertl
agreed
21:45
gcolburn
I think the XYZ values of the chart patches have to be measured for each chart as the material, ink, etc. may defer depending on manufacturer and intent of the chart (scanner, camera, printer, etc.)
21:46
Bertl
yes, thanks
22:06
gcolburn
have you seen this? http://www.argyllcms.com/doc/Scenarios.html#PS1
22:06
Bertl
soo, just to understand the chart (IT8)
22:06
se6astian
on my way to bed
22:07
Bertl
we agree that GS00 is white, yes?
22:07
se6astian
will take new captures of the it8 tomorrow
22:07
se6astian
please send me an email if you need any particular shots
22:07
Bertl
i.e. the first monochrome block at the bottom
22:07
se6astian
as I need to return the lamps on friday
22:07
Bertl
well, try to make as many snaps as possible
22:07
Bertl
and keep good documentation
22:08
se6astian
but with what variations? :)
22:08
se6astian
I will
22:08
Bertl
always do several shots without changing the position
22:08
se6astian
noted
22:08
se6astian
good night!
22:08
Bertl
so that we can remove the dynamic noise
22:08
se6astian
left the channel
22:08
Bertl
gcolburn: do we agree that GS00 is white?
22:09
gcolburn
yeah
22:10
Bertl
okay, so when I take those values as XYZ (from the IT8.cht) and convert it to sRGB, what values can I expect?
22:11
Bertl
because the onlineconverter I found gives me #FBE8CC
22:12
gcolburn
well, assuming the conversion is correct then that's what you would get if the incident light from the patch really was the XYZ value from the chart
22:13
gcolburn
by the way, I read this:
22:13
gcolburn
"Well behaved input devices will probably give the best results with a shaper/matrix profile, and this may also be the best choice if your test chart has a small or unevenly distributed set of test patchs (ie. the IT8.7.2). If a shaper/matrix profile is a poor fit, consider using a LUT type profile."
22:13
Bertl
so the chart shouldn't be white when it would be perfect or how to interpret this?
22:14
Bertl
I would have expected the XYZ 'white' to result in (s)RGB white or at least a gray, no?
22:15
Bertl
the assumed 'black' also gives
22:15
Bertl
#0E090A which is a dark brown
22:17
gcolburn
hmm
22:17
gcolburn
it also depends on your monitor being calibrated
22:18
gcolburn
I finally got my colorimeter to work a month ago on my computer and got my NEC LCD profiled. the channels were definitely off :)
22:19
gcolburn
but as far as the numerical values go, I would initially think so it would be 255, 255, 255 for example but I'm not entirely sure
22:20
gcolburn
I've noticed when I view the DNG there is a brownish ting to the grayscale patches
22:21
gcolburn
kind of brown. i've always thought it was due to the fixed pattern noise. so not sure
22:29
gcolburn
here's what the Argyll docs say about the .chrt file
22:29
gcolburn
"The XYZ values are assumed to be scaled to a maximum Y value of 100. An expected color value doesn't have to be provided for every defined sample box, nor is it expected to be accurate - it just has to represent the approximate expected color. (Actual chart reference values are provided as a separate CGATS file to scanin)."
22:31
jucar
left the channel
22:38
Bertl
I think we can agree that #0E090A is not black regardless how my monitor is calibrated (as it is not involved :)
22:39
Bertl
anyway, just trying to figure out what the it8.cht values actually mean
22:42
gcolburn
yeah
22:42
gcolburn
well according to that documentation, they don't have to be accurate
22:43
gcolburn
as its read in from another file
22:43
gcolburn
which I presume is the measured from the manufacturer (trying to verify that)
22:44
Bertl
so where does the CGATS file come from?
22:44
dmj_nova
joined the channel
22:44
gcolburn
its a more general format not specific to Argyll
22:44
gcolburn
I'm pretty sure its the R100604.txt file
22:44
gcolburn
but I want to verify that
22:45
Bertl
so the it8.cht is not used at all for the calibration? except for where to place what color box?
22:45
gcolburn
http://www.colorwiki.com/wiki/CGATS.17_Text_File_Format
22:45
gcolburn
yes, what you said is my understanding
22:46
gcolburn
the file from faust is in the CGATS format
22:46
gcolburn
so for coming up with your own calibration
22:46
gcolburn
take the values from that file
22:47
gcolburn
so GS0 is 76.53 79.65 68.26
22:48
Bertl
which is more reddish than the beige we had before, but otherwise definitely not white
22:51
Bertl
unless I'm completely wrong, white should map to ~95/100/109 in XYZ
22:51
guesst
so where is the issue? why do gray references appear non gray ?
22:51
gcolburn
where do you get that from?
22:51
Bertl
from the transformation matrix
22:52
gcolburn
with what input value?
22:52
Bertl
#FFFFFF as RGB
22:53
Bertl
guesst: the issue/question is, why would the IT8 chart purposely use non-gray values for gray fields?
22:53
Bertl
(i.e. colors in the gray section)
22:54
gcolburn
my guess is you can't manufacture a perfect gray
22:54
Bertl
in this case the white? hello?
22:55
Bertl
I would say, the white photo paper is pretty white, no?
22:55
Bertl
and not red or orange
22:56
Bertl
but okay, let's assume the printed IT8 chart has orange-beige in the white field
22:56
gcolburn
yeah, but to what accuracy/precision?
22:56
Bertl
there must be some definition what color it actually should be
22:56
gcolburn
that's why paper profiles are important
22:56
gcolburn
yeah
22:57
Bertl
i.e. it should be 'white'
22:57
gcolburn
its in the IT8 standard
22:57
gcolburn
i'm trying to find a copy
22:57
gcolburn
so we can read it
22:57
Bertl
but that value is not represented in the it8.cht for whatever reason, yes?
22:57
Bertl
i.e. they put some color there which they know is different from what it should be, do I get that right?
22:58
Bertl
sounds a little arbitrary to me
22:58
gcolburn
I have no idea how they designed the chart. but obviously the goal is to cover a wide gamut of colors
22:58
Bertl
I can accept that the it8.cht color data is just to show achart
22:59
Bertl
i.e. visualize the chart, but why would you put 'wrong' colors there?
22:59
gcolburn
I have no idea. I thought that was odd
23:03
gcolburn
color science is very complicated. some day when I have the time I'd like to read a good book on it
23:04
Bertl
I think it is made unneccessarily complicated by a multitude of (half)standard and accidents
23:05
gcolburn
yeah. I think its that way in many fields though
23:05
gcolburn
for example in radiation therapy most aspects of "dosimetry" are defined by standards
23:05
gcolburn
which change over time
23:06
gcolburn
usually trying to account for more things that had to be neglected previously
23:06
gcolburn
I'd like to try running shots from various cameras through Argyll and see what we observe
23:18
Bertl
well, I don't think that we will get _any_ raw data from those cameras
23:19
gcolburn
yeah
23:19
Bertl
i.e. it will always be somewhat processed
23:19
Bertl
anyway, off to bed now ... have a good one everyone!
23:19
gcolburn
goodnight!
23:43
dmj_nova
left the channel
23:50
gcolburn
left the channel