Dual ISO - massive dynamic range improvement (dual_iso.mo)

[DeafEyeJedi]

Got it @Audionut -- Actually saw that thread and at first I though it was more Dual-ISO related but after your pointers I'll try reading the entire thread thoroughly again and will stick to that thread instead.

Thanks!

[neavissa]

Hi,

Maybe someone can take the time to clarify something for me?! I thought I had it all figured out, but for some reason, I am totally lost now. 

I thought that in order to get those nice HDR picture as posted in post #1, all you have to do is, shoot them in your camera, take the RAW file, drag it onto cr2hdr.exe and the end result will be a killer looking HDR .dng file??? I guess I am wrong, right?! The way it looks to me is, that I am THEN supposed to take the .dng file and import it to a Photo editing software like Lightroom or Photoshop and THEN create the final HDR image?! Is that correct?!

The other thing I am not getting is, what is the cr2hdr Lightroom plugin for?!

SO all in all, I am not sure what software does what and if any other steps have to be taken, in order to get those nice HDR images?!

thanks,

G

p.s. YES, I read this thread, not all of it, googled and tried what not, but I cannot figure it out! I am lost!

[garry23]

Neavissa

You might wish to reread what Dual ISO is all about.

Put simply, dual ISO achieves a two image bracket but in a single frame.

The two images are captured at the same time and interlaced in the image, hence the cr2hdr process is taking the interlaced data and creating a new digital negative, ie a DNG.

The interlaced images are separated in exposure space by different ISOs, ie the two ISO, interlaced  brackets, have the same aperture and shutter speed.

The DNG negative will definately need post processing, as any RAW image will.

The advantage is that the dual ISO will have 2-3 stops of additional dynamic range.

For optimum capture use ETTR and dual together, ie push the tonal data to the right, without overexposing, and 'fill in' the shadows with dual ISO.

[neavissa]

Neavissa

You might wish to reread what Dual ISO is all about.

Put simply, dual ISO achieves a two image bracket but in a single frame.

The two images are captured at the same time and interlaced in the image, hence the cr2hdr process is taking the interlaced data and creating a new digital negative, ie a DNG.

The interlaced images are separated in exposure space by different ISOs, ie the two ISO, interlaced  brackets, have the same aperture and shutter speed.

The DNG negative will definately need post processing, as any RAW image will.

The advantage is that the dual ISO will have 2-3 stops of additional dynamic range.

Thanks for the reply. I got all of this so far, but I am still not sure what the difference is between using cr2hdr.exe, or the Lightroom plugin?! It seems like both "methods" achieve the same thing, right?!

For optimum capture use ETTR and dual together, ie push the tonal data to the right, without overexposing, and 'fill in' the shadows with dual ISO.

I am going to have to look up how to use ETTR and dual together...

thanks,

G

[walter_schulz]

Dual-ISO LR plug-in is in fact using cr2hdr/cr2hdr20.
It's kind of a wrapper with a GUI + integration in LR.

[garry23]

Neavissa

Walter has clarified the .exe use.

As for ETTR there are two basic ways of integrating it with dual.

You can get ETTR to automatically call it when it thinks it is required, ie when certain criteria are met.

Personally, I prefer to make this decision myself. For instance, I use ETTR to set the base exposure, at ISO 100, and take a dual with this ETTR exposure setting.

A nice feature is that you can tell duel to only take a dual every other shot, hence take two images and one will be dual and one will be non-dual.

[mothaibaphoto]

I reach the limit on the command line length while try to run cr2hdr-20bit.exe --same-levels - "The filename or extension is too long". Please, folder, or file mask option.

[walter_schulz]

Open commandline
subst X: C:\my_very_long_and_therefore_limited_path_length_which_will_cause_trouble_with_this_application_but_there_is_a_workaround

[mothaibaphoto]

I have dual ISO video with several thousand frames in each MLV file. I want to process every shot with same black levels, or whatever else --same-levels do. I can't shorten pathnames anymore.

[Walter Schulz]

[ ] You have tested what I wrote.
You can assign any directory (=path name) to any drive letter not yet occupied.

[mothaibaphoto]

You misunderstand the problem. MLV dump produce files with ten symbols at least. Like this one - 000000.dng. I need to pass several thousands filenames in one command line. Doesn't matter, how short the pathname to folder with all these files - the command line gets too long due to files quantity, not the redundantly long folder name i put them in.
When i deal with ffmpeg, or, let say adobe DNG converter, I can pass folder and/or file mask as parameter. I ask the same thing for HDR tool. There is NO easy workarounds.

[dmilligan]

you can accomplish this with xargs and pipes on *nix operating systems:

Code Select Expand


find /path/to/dir/with/images -name '*.dng' | xargs cr2hdr --same-levels


you can apply the same whitelevel to all DNGs with exiftool in the same way (this is all that --same-levels does)

Code Select Expand


find /path/to/dir/with/images -name '*.dng' | xargs exiftool "-WhiteLevel+=50000" -overwrite_original


there's probably a similar way to do this on windows, but I'm no windows shell expert

[a1ex]

Wrong answer, because --same-levels only works if all the filenames are passed in a single command line. But xargs will pass each .dng to a separate instance of cr2hdr, which effectively cancels the effect of --same-levels.

And on *nix, command line length is less likely to be an issue anyway. On my system is 2 MB, and on Mac it seems to be around 256K.

For Windows, one has to implement a FindFirst/FindNext loop to handle wildcards. On *nix, these are expanded by the shell.

For the exiftool method, no workarounds should be required. Note the command is a little different:
http://www.magiclantern.fm/forum/index.php?topic=7139.msg114254

[Danne]

Find args is the best. What got me starting my unix playing thanks to dmilligan.

About same levels.

If you run command below it will take the whitelevel from your first file and apply to all the rest of your files. If you  delete the line -overwrite original it will keep a copy of your file. I had some problems on external drive with exiftool.

exiftool -tagsfromfile *.DNG -exif:whitelevel -overwrite_original

Simply write cd drag your folder here exiftool -tagsfromfile *.DNG -exif:whitelevel -overwrite_original hit enter.


This mac app workflow will also correct same levels when run in folders with dng files.
http://www.magiclantern.fm/forum/index.php?topic=13512.0


*update. Sorry, didn,t notice you were looking for a windows solution.

[mothaibaphoto]

Thank you all.
Apologies I didn't find this was explained in details before.
@Danne: Use the /D switch to change current drive in addition to changing current
directory for a drive :
cd /D [drag your external drive folder here]

[ganselm]

I'm using Dual ISO on my EOS M quite successfully for a while and  *really* like it. However, during some shots over the weekend I encountered a banding artifact after using cr2hdr.exe and cr2hdr20bit.exe (used several different versions, the result always was the same)

Here's a crop of the image:

https://www.dropbox.com/s/6rfiwz5gcawgcua/banding.jpg

and here's the according debug black frame I saved.

https://www.dropbox.com/s/7edcyuc0yawq0wc/black.jpg

There's a --no-stripe-fix option which sounds like maybe this is already known? But unfortunately it seems as if it doesn't work.

Could someone give me a hint where to find the source code of cr2hdr?? Is this one the newest one? (bitbucket is not working right now, so I cannot open the link):

https://bitbucket.org/hudson/magic-lantern/branch/cr2hdr-20bit

I've some background in that field and would like to contribute if I'm able to get the stuff compiled.

Any suggestions? I actually traveled to the Anza Borrego desert staying in the desert during the night listening to coyotes and rattlesnakes to capture some night shots and would really like to rescue those pictures....

[a1ex]

Can you upload the CR2?

[ganselm]

Thanks for the quick reply a1ex. This one:

https://www.dropbox.com/s/yqpstzr1k30kxoh/_MG_2113.CR2?dl=0

is a similar shot with the same behavior after converting to DNG

[Randallsart]

New to ML. I have a question. After I export from LR, then what?

[Audionut]

Post process.

[Randallsart]

okay I figured it out. I could not find the dng file. I was thinking it would automatically re import into LR.

[a1ex]

[...] I encountered a banding artifact after using cr2hdr.exe and cr2hdr20bit.exe [...]

As you have guessed, the issue appears during the black level correction step (black_subtract, most likely the first half). It has nothing to do with --no-stripe-fix.

The OB areas appear correct though, so I'm not yet sure what causes it.

Edit: found the problem - a hot pixel in the top optical black area! Solution: use median instead of averaging.

The source code link from your post is correct.

[ganselm]

Wow a1ex, thanks for your quick fixing.

I'm currently travelling and will try to build the stuff when I'm back. Would you be able to build a Windows executable for me beforehand or do you know someone who has the stuff ready for compilation on a windows machine?

Thanks again!

[a1ex]

I didn't fix it yet, only found the problem and suggested a fix.

[ganselm]

a1ex committed d397c38 5 hours ago

but now you did =)