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Messages - a1ex

#8276
Tragic Lantern / Re: Raw video on 50d and 40d
July 19, 2013, 08:58:18 AM
Quote from: mjstudio on July 19, 2013, 02:55:10 AM
Every overexposed element gets stripes.

Can you upload a DNG converted with raw2dng from the horse video, and one second (or less) of a raw test shot (the RAW file) showing the same problem?
#8277
It took 3 months from the point I knew how to compile ML until I had courage to run it on my camera ;)
#8278
Raw Video / Re: raw2dng changes
July 19, 2013, 08:38:40 AM
Only for dual ISO.
#8279
@dubzeebass: can you upload a sample? (less than 1 second of video, if possible).

Did it work better with a previous version?
#8280
Raw Video / Re: Help finding Framing Options
July 18, 2013, 10:46:18 PM
The guides are not always up to date; all this is bleeding edge and changes often.
#8281
I can alternate the exposures, but the postprocessing will be a lot more complex. It should help with highlight aliasing (because the shadow one is pretty much solved).

In some videos, the exposure pattern is moving, and in others it's fixed. I don't know yet why this happens.

I don't know how to alternate ISO for every single line - if you look in the paper, all I do is changing a register to low-high or high-low. The ADTG chip does the rest.
#8282
Raw Video / Re: Help finding Framing Options
July 18, 2013, 10:29:21 PM
Why do you need it? just press the zoom button...
#8283
Looks quite nice.

Did you use ML post deflicker? do you still have the sidecar files for these two shots?
#8284
To choose other options, just flip the conditional defines from the source code (INTERP_*). For shadow aliasing, adjust f_shadow.
#8285
Nice, which one do you like from Driftwood's test?

Another tip: in crop video mode, it will skip only 2 lines at a time (instead of 6). Therefore, you can expect a lot less aliasing.

You can also record at higher vertical resolution (1320) and then resize it to something lower. It should hide some artifacts.
#8286
Figure 8 shows where you get full resolution.

With my latest modifications, you also get almost full resolution in deep shadows, but with more noise (see my previous post).
#8287
Here's how I've got the 3 pictures:

a) should have no shadow aliasing (shadows were handled as if they were midones). To get similar results, use this raw2dng: http://acoutts.com/a1ex/raw2dng_shadow100.exe

b) is a 50% blend between a) and the high ISO image. Less noise, a little aliasing. http://acoutts.com/a1ex/raw2dng_shadow050.exe

c) is 25% a) and 75% high-iso. Therefore, even less noise, but a little more aliasing. http://acoutts.com/a1ex/raw2dng_shadow025.exe

By default, shadows used data from high ISO only. This gets minimal noise, but it seems to have serious problems with aliasing.

Of course, now the formula from Horshack's friend should be valid for case a).

@MA Visuals: can you repeat your test with these 3 raw2dng's? Just post-process the same video with them.

Latest cr2hdr uses 50% blend (link in first post).

@ajay and @audionut: can you develop your test shots (the same pictures that you posted earlier) with latest cr2hdr?
#8288
Regarding shadow aliasing: which of these 3 pics would you choose, and why?

http://acoutts.com/a1ex/shadow/a.jpg
http://acoutts.com/a1ex/shadow/b.jpg
http://acoutts.com/a1ex/shadow/c.jpg

Just for your reference, to get an idea of the noise levels:
ISO 100 half: http://acoutts.com/a1ex/shadow/iso100.jpg
ISO 1600 half: http://acoutts.com/a1ex/shadow/iso1600.jpg
#8289
Raw Video / Re: Raw2dng disapeared from Bitbucket !
July 18, 2013, 10:35:24 AM
In the sticky topic where it was from the beginning...

http://www.magiclantern.fm/forum/index.php?topic=5404.0
#8290
@driftwood,

Can you upload 1 second (or less) of raw video (the RAW file, not the DNGs), where mean23 gives better results than the default median?

In all my tests, median was a lot better on edges (see my bugfix above - that's an interpolated image, 2 lines from the sensor, 2 interpolated). I did not shoot power lines, I don't like them :P
#8291
No need to use memcheck, it's only for developers.
#8292
Just found a bug in the interpolation code near clipped highlights. Updated converters in first post.

Before (half-res ISO 1600 interpolated):


After (half-res ISO 1600 interpolated):


Please remember that in video mode it's skipping 6 lines at a time, and in photo mode it's skipping only 2 at a time. So my suggestion is to try to post photo samples too; videos are not the strong point for this method.

#8293
@horshack,

I don't know who theSuede is (he seems to know some stuff though), but please ask him to read the PDF. I'm pretty sure he didn't.

In deep shadows I only use data from the higher ISO, therefore his averaging formula does not apply here.

@ajay,

Of course I need the original files. Use some file sharing service.

@all,

For aliasing, there's nothing you can do to remove it completely; but you can reduce the artifacts by using a better interpolation algorithm. Even the debayering method you use in your raw software matters, so try to fiddle with it.

Or, use less aggressive settings (e.g. ISO 100/400) to minimize the areas where aliasing may appear.

Here's an alternate cr2hdr/raw2dng, with the mean23 interpolation algorithm (see the source code for details). It has more jagged edges in the Batman shot and my other test shots, but should handle trees and power lines a bit better.

cr2hdr_mean23.exe
raw2dng_mean23.exe

You can further reduce shadow aliasing by increasing the overlap amount (you'll get more noise). See the paper and the source code for details.
#8294
Yes, some samples will be useful.
#8295
Here, a different interpolation method may give different results. Try choosing another one (in cr2hdr.c, there are some defines at the top).

I guess plain averaging will handle this one a bit better than medians.
#8296
Updated cr2hdr.exe, works for me under Wine. The dependencies (dcraw and exiftool) are included in the zip file.
#8298
Time for the first real image quality improvement in ML history :)

Here's a trick that samples half of the sensor at ISO 100 and the other half at ISO 1600, for example. If you mix these two, you can get almost the entire dynamic range the sensor is capable of (around 14 stops). 5D3/7D only. Now it works on most cameras!

There are no motion artifacts; not even a difference in motion blur for the two exposures. So, it works well for fast moving subjects.



Please post your samples here -> Thread photos dual ISO

More samples on Flickr (tag: Dual-ISO)
Tutorial - Guide to using Dual ISO Mode on your Canon 5D Mark III
Open Source Brings High-End Canon 5D MK III Dynamic Range Closer to Nikon D800
Dual ISO vs Exmor: on CanonRumors, reddit, POTN and FredMiranda.

Code
- dual_iso module
- recent nightly builds should have this working on most cameras

Technical doc
- dual_iso.pdf (in-depth description of how it works)
- See also: ADTG and CMOS discussion

Warning
This code changes low-level sensor parameters. In the technical doc you can see how this method messes with the feedback loop for optical black, for example. Since the original implementation, many people have tried it (including timelapse), with very few side effects reported (e.g. more hot pixels than usual on long exposures). However, that's not a guarantee.

We don't pay for repairs. Use it at your own risk.


Usage
- Select one ISO from Canon menu, the other from Dual ISO submenu.
- Expose to the right for the lower ISO (usually ISO 100). Maybe darken 1 stop from there.
- Start at ISO 100/800.
- Try a larger gap for really extreme situations, or a smaller gap for better midtone detail (less aliasing).

Histograms, ETTR, playback tricks

- ETTR integrates with dual ISO (just enable both). It will use dual ISO only in high dynamic range scenes. Adjust the SNR limits to let the algorithm know what exactly is a "high dynamic range scene" and to fine-tune the balance between midtone/shadow noise and highlight aliasing.

- Raw zebras: weak markers appear where only one of the two ISOs is overexposed (likely to get aliasing), strong markers appear where both ISOs are overexposed (there's no more detail in these areas).  See here for examples.

- Raw histogram will use the darker exposure. Consider the brighter one as some sort of shadow recovery.
- JPEG zebras/histogram are totally unreliable.
- In photo LiveView you will see the ISO from Canon menu. In movie mode, you will see horizontal lines.
- Playback in 1x will show some sort of HDR preview. At certain zoom levels, you'll be able to see only one of the two exposures, at very low resolution.
- The dynamic range indicator from the histogram is not accurate. (solved!)

Postprocessing

- Reference converter: cr2hdr.c (Windows: cr2hdr.exe). It requires dcraw and (optional) exiftool in your executable path (they are in the zip). Drag and drop the CR2 files over cr2hdr.exe.

- For RAW video files, use the following commands in a terminal:

mlv_dump clip.mlv --dng --no-fixcp --no-stripes
cr2hdr --same-levels *.DNG


- GUI frontends:
   - Lightroom plugin (WIN/MAC)
   - BarracudaGUI (WIN)
   - Script for multiple instances of cr2hdr (WIN, VBScript)
   - Mac GUI for cr2hdr: OSX_cr2hdr_app.zip and OSX_cr2hdr.zip
   - MLV to DNG Batch Converter (WIN, video only)
   - MLP (MAC)

- To get a natural HDR look: try my automatic color grading script.

Price to pay
- Half resolution in highlights and shadows
- Aliasing and moire - of course, in highlights and shadows
- You can no longer check critical focus when zooming in

Samples

This is actually a video frame from 5D Mark III. Here's the DNG.
Bottom-left: ISO 100. Top-right: ISO 100/1600.
Credits: Luke Neumann.



The next one is a still photo from 5D Mark III. Here's the DNG and the original CR2. ISO 100/1600.






Questions? Read the pdf first. The mystery should clear up, I hope.

That's it. Looking forward to your samples.
#8299
It should be quite obvious that you should not use auto bracketing for timelapse. Use full manual settings.
#8300
Wait a minute, you don't have DNG silent pics in 6D?