#apertus IRC Channel Logs

morning folks!

MEETING TIME!

Bertl notified me he has an urgent appointment currently and will likely miss the meeting

sure

In general, these were captured with a as uniform as possible light source and averaged over 256 frames

(the flatfields were captured at ~2ms, ~3ms, ~7ms and ~14ms)

the first thing I looked at, was the standard deviation per pixel over the 256 darkframes for the exposures

this is roughly the same as plain darkframes

https://files.niemo.de/flatfield.png

visually the pixel values mostly look similar per column, but seem to change for the columns

using only pixels in even columns and rows (to select pixels with the same color filter)

(looking a column 0, 32, 64, at 1, 33, 65, etc)

plotting these one gets something like this: https://files.niemo.de/column_wise_averages_1.9932959999999997.png

https://files.niemo.de/column_wise_averages_6.996432.png

whoops this one: https://files.niemo.de/column_wise_averages_13.993392.png

so the next step is comparing the flatfields with different exposures to each other

this is however not always the case

the ones that are not seem to only occur in odd rows

it seems that these "nonlinear" pixels are in general a lot less sensitive than the "linear" ones

https://files.niemo.de/corr_1.9932959999999997_by_13.993392.pdf

https://files.niemo.de/corr_6.996432_by_13.993392.pdf

in these histogram we can clearly see these two groups of pixels

indeed the location of these "nonlinear" pixels seems to follow a pretty strong pattern

https://files.niemo.de/weird_pixels_even_rows_odd_cols.png

https://files.niemo.de/weird_pixels_odd_rows_odd_cols.png

(there are four images, because each image only shows pixels with the same color filter)

very interesting

I will create an image acquisition script soon to gather more data about how the calibration images are captured + more metadata

- more different exposure times

- capturing a couple of reference images for each capture with axiom_snap

all noted

assuming a standard deviation of 6.2, the standard error of the mean is 6.2 / sqrt(n)

ahh

that would be great for upload sizes!

yes

Ill look into adding that feature

regarding the light intensity levels, there is the axiom_histogram tool, https://wiki.apertus.org/index.php?title=AXIOM_Beta/Manual#Image_Histogram_Data but its output is not meant to be human readable on the CLI

to see the current exposure levels of the live image

a webui addition maybe?

Does that work while streaming raw hdmi currently?

its possible to also capture a axiom_snap while raw streeaming

but you get output from several frames as writing the snap is not as fast as HDMI output

which would not be a real issue for the histogram graph

does it not lock the memory buffer until it is done with computing the histogram?

so while it writes the image changes

then a block of lines from frame 2....

I dont think cmv_snap does it on its own

then no issues and only brief stream interuption

anyway, just a convenience details for the histogram

alternatively would it be simpler to add a histogram or something even more simplified in the recorder?

as overlay

in theory that should not bee that hard

quick updates from me:

the wiki has been upgraded and new theme

(fyi, I just noticed that https://wiki.apertus.org/index.php/CMV12000_Register_Blocks is broken)

infographics, etc.

message me if you want to take part

next topic

we now have two weeks to apply again for 2022

and define tasks, etc.

as the idea page is the central part of the application

https://forum.openhardware.science/t/apply-here-for-gosh-s-2022-collaborative-development-program-round-1/3380/2

and involve a few early adopters to get one in the process

anyone else with news to share?

MEETING CONCLUDED

se6astian: vup: the logic for locking a buffer is already there, it just isn't used in the snap tool for now, so it should be fine to lock an arbitrary buffer down first, then simply dump the buffer e.g. with memtool instead of running a snap

thats sounds like a good idea

yeah

(which should be done after the capture sequence I guess)

vup: one question, you mentioned the nonlinearity is independent from the exposure time

What I meant was, that the pixels that show this behaviour are always the same and do not change with changing exposure time

because basically with a dark frame we do a single point calibration, with a dark and flat a two point (linear) calibration and only with different flats (exposure time or light intensity) we can do a multipoint (nonlinear) calibration

what I was also wondering is, what happened to the light sphere we hacked together? maybe this might be helpful with the flats?

ah, might be and would make sense

its stored in the office and as big as my entire desk so I am afraid currently not practical

btw just saw an article about the man of spheres were we also got the parts for the integrating sphere

interesting, glad to read they somehow survived after all, I remember getting the notifications that they will close down sometime before 2020

no they "kept the ball rolling"

seems like it ...