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 ISOMore samples on Flickr (tag: Dual-ISO)Tutorial - Guide to using Dual ISO Mode on your Canon 5D Mark IIIOpen Source Brings High-End Canon 5D MK III Dynamic Range Closer to Nikon D800Dual 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 discussionWarning
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
SamplesThis 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.
