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Thread started 01 Oct 2013 (Tuesday) 11:06
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Magic Lantern - Dual ISO readout

 
kirkt
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Oct 21, 2013 22:58 |  #31

And a blend of the two...

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tzalman
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Oct 22, 2013 04:02 |  #32

Kirk, are you keeping abreast of the work a1ex is doing on CR2hdr? The latest version available through the link in the first post of the DualISO thread is from Oct. 15, but towards the end he links to a version from a couple days ago that uses the Amaze demosaicing and seems to have less aliasing in the first few shots I have tried on it. It is also a smoother rendering, less contrast. I haven't decided yet what that means regarding detail.


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kirkt
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Oct 22, 2013 07:17 |  #33

I'll check. I am on a Mac. I usually go to the bitbucket repository and grab the Mac cr2hdr (v 1.5 beta at this point, 11 Oct 2013).

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kirkt
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Oct 22, 2013 08:45 |  #34

It looks like the AMAZE implementation:

http://www.magiclanter​n.fm …ic=7139.msg8406​8#msg84068 (external link)

is A1ex's experimentation in the PC version only. I imagine it will finds its way to the mac version.

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kirkt
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Nov 11, 2013 19:31 |  #35

AMAZE is now utilized in the latest Mac cr2hdr.

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MedicineMan4040
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Nov 12, 2013 01:32 |  #36

Fascinating....but overwhelming for someone (like me) who has just installed ML on a 6D and so far only used the intervalometer! The pic processed via Photomatix looks incredible.
But how/where to even begin this process?
I'm using ML 2.3, is this duo-iso capability already there?
I need a step by step!
and THANKS for bringing this to our attention. first thing I thought of was the how wrong the canon sensor dynamic range bashers really are!


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tzalman
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Nov 12, 2013 05:25 |  #37

I'm using ML 2.3, is this duo-iso capability already there?

No, because it is still in development. To get it you need to download a nightly build and enable it in the Modules menu. Read the first post here:
http://www.magiclanter​n.fm/forum/index.php?t​opic=7139.0 (external link)
The Dual ISO shots need to be run through the cr2hd.exe converter. You do this by having the converter, dcraw.exe, exiftool.exe and the photo files all in the same folder and then dragging the photos onto the cr2hd icon. There are also later versions of cr2hd that A1ex posted up in the thread as he created them, I am currently using the one called cr2hd-hot which is here: http://acoutts.com/a1e​x/cr2hdr-hot.exe (external link)

first thing I thought of was the how wrong the canon sensor dynamic range bashers really are!

Well, the extra DR is obtained only by forcing the camera to do things that Canon never intended and the sensor still doesn't have the range and low noise of the Sony/Nikon sensors.


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Nov 12, 2013 05:41 |  #38

OK roger all of that :) and thanks.
In theory though....Canon didn't intend yet the sensor is capable, agreed?
the ML team still fascinates me....as does the Canon team who considers them vapor.

Did read this though 'Therefore, it's safe to assume it can fry the sensor or do other nasty things'....
hmmmm


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kirkt
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Nov 12, 2013 08:36 |  #39

If you are already using ML for the intervalometer, you are risking the camera's being fried and other nasty things.

Learn to remove the battery if the system locks up or, if you turn the camera on and nothing powers up. Removing the battery stops the infinite loop that can heat up the camera, and resets the camera - after that you are usually good to go.

As Elie said, the Dual ISO concept is that, through the magic of firmware, the sensor can acquire a single shutter release of data at two ISOs simultaneously. So, you expose for one ISO such that the alternate ISO provides extra data - for example, if I set the camera at ISO 100 and expose for highlights at ISO 100, I can set the alternate ISO for 800 and get 3 stops of shadow detail simultaneously. How can this be? Well, ISO is really more of an electronic amplification than anything else, so if you know how to modify the way the camera reads data off of the sensor, you can make it read two lines of sensor sites at ISO 100 and then the next two lines of sensor sites at ISO 800 ... and repeat.

Because you have monkeyed with the data, you have alternating stripes of two exposures in a single raw ".CR2" file. So, you need to convert this striped raw file into a single, continuous file. In the Dual ISO workflow, this is accomplished by using the "cr2hdr" application. It will demosaic the raw file and do some magic to deal with inherent issues associated with the striping of the two exposures. It combines the exposures so that the dynamic range of the data is increased according to the noise in the shadows. It will output a DNG file whose appearance is that of the lower ISO exposure (darker) that is now ready for standard raw workflow processing. However, when you boost the mid tones and shadows to tone map the data, the shadows are blissfully noise free (at least as if you shot them at the higher ISO) and you can manipulate the data with almost reckless abandon. This concept is similar in theory to the "Zero Noise" approach to raw exposure combination, as authored by forum member _GUI_ (Guillermo Luijk). See his excellent website on the topic here - "Zero Noise - Virtual Raw":

http://www.guillermolu​ijk.com …e/virtualraw/in​dex_en.htm (external link)

There is very little difference between using the Dual ISO approach to shooting and regular raw shooting, in terms of exposure and camera settings. Add to this the fact that ML gives you a raw histogram and auto ETTR, and the ability to specify a true UniWB if you want to, and raw shooting is even more powerful and precise than ever before.

Very clever.


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tzalman
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Nov 12, 2013 15:32 |  #40

MedicineMan4040 wrote in post #16444739 (external link)
OK roger all of that :) and thanks.
In theory though....Canon didn't intend yet the sensor is capable, agreed?

Nope, not agreed. As Kirk explained, the sensor remains the same and continues to function just as it did before. The Dual ISO adaption is performed downstream during the analog amplification of the signal. IOW, it would be possible, at least in theory, to do a similar hack to a Nikon D800 and get 17 stops of DR instead of its normal 14 stops.


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kirkt
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Nov 12, 2013 18:08 |  #41

Here is a 200% crop of a Dual ISO raw file prior to converting it to DNG with the cr2hdr application. In this image, the data are linear, with a UniWB and untagged color space. You can see the striped pixel pattern pretty clearly in the alternating ISO data.

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Nov 12, 2013 18:57 |  #42

And here is the image processed in cr2hdr and a simple default raw conversion in RPP. Pretty impressive magic, eh?

kirk


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kirkt
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Nov 12, 2013 22:05 |  #43

Here's a previous example, tone mapped in Photomatix 5 beta.

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Nov 12, 2013 22:32 |  #44

Indeed very impressive magic, and the ML team will not stop conjuring!
And honestly no real world worries about bricking/frying my 6D, insured against loss :) Plus it's running the intervalometer quite smoothly.


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Nov 14, 2013 21:23 |  #45

tzalman wrote in post #16446168 (external link)
IOW, it would be possible, at least in theory, to do a similar hack to a Nikon D800 and get 17 stops of DR instead of its normal 14 stops.

I don't think this is true. DualISO works because the read noise at high iso is much, much lower than at low ISO. For Sony sensors this is not the case, which is why DR drops almost linearly with ISO.

So at low ISO Canon read noise is much higher than the D800 - thus limiting the DR. At high ISO it is lower, hence the better S/N of the Canons at high ISO.

The ratio of the decrease of read noise and ISO is what also determines the maximum useful ISO to use with DualISO (~800 for a 7D and ~1600 for a 5DII). Using ISO's above that doesn't help because the decrease in read noise isn't enough to offset the ISO increase.

I know that wasn't the best explanation, but should give you the idea for searching (or Kirk can explain better with numbers no doubt).


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Magic Lantern - Dual ISO readout
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