Vertical stripes revisited (5D Mark III)

Started by a1ex, August 24, 2016, 11:10:46 AM

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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.
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?
5D3.113 | 5D3.123 | EOSM.203 | 7D.203 | 70D.112 | 100D.101 | EOSM2.* | 50D.109

Danne


DeafEyeJedi

Sorry guess I misread your post and I'll sheesh up until @MarS shines upon!
5D3.113 | 5D3.123 | EOSM.203 | 7D.203 | 70D.112 | 100D.101 | EOSM2.* | 50D.109

a1ex

Are you asking what is the difference between those two?


(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:

-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 --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


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.