Vertical stripes revisited (5D Mark III)

[Danne]

I,m trying to get the concept of creating a flatframe together with a flat dark.

MarS put this up a few posts up.

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mlv_dump -s dark.mlv -o flat-dark.mlv flat.mlv
Do I average the flat.mlv and the dark.mlv before doing the darkframe subtraction from the flatframe above? I mean the whole workflow would look something like this.
1 - mlv_dump my_flat.mlv -a -o flat.mlv
2 - mlv_dump  my_dark.mlv -a -o dark.mlv
last step
3 - mlv_dump -s dark.mlv -o flat-dark.mlv flat.mlv

I would now have the darksubtracted flat_dark.mlv? Or do I skip step 1 and 2 and go straight to 3 meaning I would work with unaveraged flatframe and darkframe footage and instead I average the flat.mlv as a last step in the process?

[DeafEyeJedi]

Basically is it better to go...

•MLV > FlatFrame > DarkFraming Avg as Danne suggested or...

•MLV > DF Avg > FF?

[Danne]

That is not what I,m asking.

[DeafEyeJedi]

Sorry guess I misread your post and I'll sheesh up until @MarS shines upon!

[a1ex]

Are you asking what is the difference between those two?

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(f1+f2+f3+...+fn)/n - (d1+d2+d3+...+dn)/n
(f1-d1 + f2-d2 + f3-d3 + ... + fn-dn) / n

The only difference would be in round-off errors (one does two integer divisions, other does one). I doubt you'll be able to see it in practice (maybe only if you are stacking a lot of frames).

In this case, you may also want to add some rounding to the integer division:

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-value /= average_samples;
+value = (value + average_samples/2) / average_samples;

Or you may want to work with higher bit depths.

[Danne]

I,m testing various ways to create the optimal flatframe. Experimenting with some clips with focus pixels on. Conclusion so far is that a single flatframe MLV seems to be enough to use together with a darkframe MLV to eliminate around 95% of the focus pixels. Close but no cegar. Yet.
Producing a flatframe+flatdark=flatframe + additional darkframe MLV doesn,t seem to add any improvement in this very test. Probably stronger use in astrophotography.
A bit tedious testing this but I soon have a half automated script workflow in cr2hdr.app which will make it very easy to create both flatframes and darkframes.

[Danne]

Been testing darkframes and flatframes and now I got some scripted automated solutions for both darkframes and flatframes in cr2hdr.app
http://www.magiclantern.fm/forum/index.php?topic=15108.msg146822#msg146822

Darkframe subtraction really cleans up color noise significantly on higher isos(example 800 iso) and flatframes evens out vignetting among other things. I ended up with a flatframe filmed at f5.6 while cat clip was filmed at f1.4.
A lot more to learn and test with in regard of creating the better flatframe. Here is an interested read about it. Note that I didn,t follow the rule.
https://photographingspace.com/how-to-create-dslr-and-ccd-flat-frames-for-astrophotography/

Original dng files here
https://drive.google.com/file/d/0B4tCJMlOYfirS2RoRV9jUGVVOE0/view?usp=sharing

Original


Darkframe subtraction added


Darkframe+flatframe added

[GutterPump]

I back on this topic after did lot of tests and shot, i noticed something strange.

The automatic stripes correction does not always work to some MLV footage that have highlight.
Sometime yes sometime no, depend the footage and maybe the exposition.

I do not know if it's related but i use the MLV_DUMP version from this link :

http://www.magiclantern.fm/forum/index.php?topic=5601.msg177064#msg177064

MLV footage was at 12bits, standard mode (no crop), on 5D mark III 113.

command line was just

Code: [Select]

--dng

I have to try with standard 14bits MLV and MLV_DUMP from last september for check if i get the same issue than 12bits.

Here two exemple of short .MLV, one with the issue, one without.

https://www.dropbox.com/s/41axdf047m16eg9/12bits-stripecorrectionwork.MLV?dl=0
https://www.dropbox.com/s/09z50zr9r9h2ety/12bits-stripescorrectiondontwork.MLV?dl=0


EDIT :

I did some tests with 14bits MLV files and older MLV_DUMP from 05SEPT.

I get the same issue. Look like the stripes fix dont work when the footage is overexposed, but sometime i need to overexpose when i do "Zone system".
Is there a solution for apply this fix even if the footage is overexposed and not just ETTR ?

Here some exemples with others shorts MLV :

https://www.dropbox.com/s/d3c5uqwmxdwck6s/overexposed_stripesfixdontwork.MLV?dl=0
https://www.dropbox.com/s/bt921vhev7qofss/ETTR_stripesfixwork.MLV?dl=0

[Danne]

How does it not work you mean? Very overexposed but seems fine?

[GutterPump]

Here an exemple with the ETTR_stripesfixwork.MLV :




Another with overexposed_stripesfixdontwork.MLV





Do you understand what i mean about this issue ?

During the process for extract DNG from the  overexposed_stripesfixdontwork.MLV with MLV_DUMP , the stripes fix don't work.

[Danne]

Understand now. Seem to work on mac

[Danne]

You,re right. Older build of mlv_dump code will work but not the latest on your selected examples. Just tested again.

[GutterPump]

Thanks Danne, i'm feel less alone hehe.

On my exemple, i did the test with MLV_DUMP from 05 septembre 2016.