Author Topic: 6D Dual Iso and more DR hack?  (Read 18790 times)

1%

  • Developer
  • Hero Member
  • *****
  • Posts: 5936
  • 600D/6D/50D/EOSM/7D
Re: 6D Dual Iso and more DR hack?
« Reply #50 on: January 20, 2014, 09:03:37 PM »
This kinda proves further the iso 128k is fake. Its Iso 6400 - another EV of gain.

Marsu42

  • Contributor
  • Hero Member
  • *****
  • Posts: 1557
  • 66d + flashes
Re: 6D Dual Iso and more DR hack?
« Reply #51 on: January 20, 2014, 09:15:31 PM »
This kinda proves further the iso 128k is fake. Its Iso 6400 - another EV of gain.

Right, after thinking about it again that would be it - Canon really simply clips 1ev by digital gain. Strange it seems to be different on 5d3, isn't it - Canon graced the big model with a "real" 12800 while the 6d is maxed out @6400?

a1ex

  • Administrator
  • Hero Member
  • *****
  • Posts: 12564
Re: 6D Dual Iso and more DR hack?
« Reply #52 on: January 20, 2014, 09:18:27 PM »
Yeah, it's pushed via ADTG gain. Override it in ADTG GUI to around 5x the original value and compare the noise stdev values from raw_diag; I got no real improvement in noise, so this gain seems to be very similar to a digital multiplication (without the roundoff errors).

Marsu42

  • Contributor
  • Hero Member
  • *****
  • Posts: 1557
  • 66d + flashes
Re: 6D Dual Iso and more DR hack?
« Reply #53 on: January 20, 2014, 09:25:57 PM »
I got no real improvement in noise, so this gain seems to be very similar to a digital multiplication (without the roundoff errors).

That's on 5d3 or 6d? Meaning both cameras don't have a real 12800 mode, or only the 6d is lacking it?

a1ex

  • Administrator
  • Hero Member
  • *****
  • Posts: 12564
Re: 6D Dual Iso and more DR hack?
« Reply #54 on: January 20, 2014, 09:36:15 PM »
5D3 and 60D. But I guess ADTG gain behaves in the same way everywhere.

Marsu42

  • Contributor
  • Hero Member
  • *****
  • Posts: 1557
  • 66d + flashes
Re: 6D Dual Iso and more DR hack?
« Reply #55 on: January 20, 2014, 09:42:58 PM »
5D3 and 60D. But I guess ADTG gain behaves in the same way everywhere.

Weeeelll, but why is the 5d3 12800 calibration smaller than 6400-1ev like it is on 6d? Sorry to be inquisitive, but this still troubles me.

a1ex

  • Administrator
  • Hero Member
  • *****
  • Posts: 12564
Re: 6D Dual Iso and more DR hack?
« Reply #56 on: January 20, 2014, 09:58:21 PM »
Because the rest is done with CMOS gain (an earlier amplifier stage).

ISO 6400 on 6D is cleaner than 5D3's 12800 (and with a lot more DR too), so there's no reason to get troubled.

http://www.clarkvision.com/articles/evaluation-canon-6d/index.html vs http://www.clarkvision.com/articles/evaluation-canon-5diii/index.html

Also, this DR trick is not going to make the 5D3 as good as unmodified 6D, because it can't reduce shadow noise. Both cameras will get a little more highlight details, but shadow noise will stay the same.

(Of course, you'll be able to ETTR a little more, and this will reduce the noise. But if you don't ETTR, you won't get any less noise.)

Audionut

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 3657
  • Blunt and to the point
Re: 6D Dual Iso and more DR hack?
« Reply #57 on: January 20, 2014, 10:09:11 PM »
(Of course, you'll be able to ETTR a little more, and this will reduce the noise. But if you don't ETTR, you won't get any less noise.)

+0.3EC will fix it!

In my ML vs Canon ISO tests, I always +0.3EC.  If Canon clips the highlight data and ML doesn't, that's Canons problem!  ML fixes it by allowing you to expose 0.3EV higher, and gain all the benefits that come with it.

I realise the scientific standpoint of understanding the effects of the gain alone.  But as a photographer, ML ISO allows me to expose 0.3EV higher.  I think it's important to point out that you do gain an increase in SNR through the entire exposure, you just need to learn to expose for ML, ie:  +0.3EC.

a1ex

  • Administrator
  • Hero Member
  • *****
  • Posts: 12564
Re: 6D Dual Iso and more DR hack?
« Reply #58 on: January 20, 2014, 10:12:03 PM »
Yes, this counts as ETTR'ing a little more.

Levas

  • Contributor
  • Hero Member
  • *****
  • Posts: 1741
  • 6d - Nightly build user
Re: 6D Dual Iso and more DR hack?
« Reply #59 on: January 21, 2014, 09:33:37 AM »
I'm confused about the 12800 iso if it's real or not on the 6d.
We're talking about the canon 6d right ? (cause I'm also seeing people talking about 60d).

I always assumed that only the high (H1 and H2) and low (L1) where fakes(fake meaning digital corrected in camera, after the data leaves the cmos).
Does this mean that when I need iso 12800 or 25600 I get just as good results in using iso 6400 and do a exposure correction in a raw editor  :o?

a1ex

  • Administrator
  • Hero Member
  • *****
  • Posts: 12564
Re: 6D Dual Iso and more DR hack?
« Reply #60 on: January 21, 2014, 09:46:09 AM »
According to the data from Roger Clark, yes.

My current theory says these ISOs are pushed analogically, not digitally. Audionut is challenging it, so we don't have a final word on this. Either way, if it's pushed analogically without any noise improvement, it's just as useless as a digital push.

You need to confirm the theory experimentally and see for yourself. Don't just believe us blindly ;)

Levas

  • Contributor
  • Hero Member
  • *****
  • Posts: 1741
  • 6d - Nightly build user
Re: 6D Dual Iso and more DR hack?
« Reply #61 on: January 21, 2014, 11:06:07 AM »
According to the data from Roger Clark, yes.

My current theory says these ISOs are pushed analogically, not digitally. Audionut is challenging it, so we don't have a final word on this. Either way, if it's pushed analogically without any noise improvement, it's just as useless as a digital push.

You need to confirm the theory experimentally and see for yourself. Don't just believe us blindly ;)

Did a not so scientific test.
Took 3 pictures in a row(didn't change focus), shutter time and f stop 3 times the same (1/4000th and f8.0), only changed the iso from 25600 down to 6400.
Openend the raw's in canon's digital photo professional (which seems more logic to me for this test then using lightroom) and bumped the exposure for the iso 6400 and 12800.
Then opened the raw's side to side to compare at 100% (6400 VS 25600) the bumped 6400 looks more harsh/crude to me. The picture loses fine detail when bumping up the iso.
Did the same again with iso 1600 VS 6400, again the bumped 1600 looks more harsh/crude, and had less fine detail.

So for now, I'm using 25600 when I need it...

Hmm should do this test again with 25600 compared to 102400...

a1ex

  • Administrator
  • Hero Member
  • *****
  • Posts: 12564
Re: 6D Dual Iso and more DR hack?
« Reply #62 on: January 21, 2014, 11:09:50 AM »
Post the raw files.

Levas

  • Contributor
  • Hero Member
  • *****
  • Posts: 1741
  • 6d - Nightly build user
Re: 6D Dual Iso and more DR hack?
« Reply #63 on: January 21, 2014, 11:25:05 AM »
How do I post them, Is it possible to upload them somewhere on the forum or do I have to put them somewhere on the internet and post some links ?

Levas

  • Contributor
  • Hero Member
  • *****
  • Posts: 1741
  • 6d - Nightly build user
Re: 6D Dual Iso and more DR hack?
« Reply #64 on: January 21, 2014, 11:38:21 AM »
Did the test with 102400 VS 25600 bumped 2 stops.

Detail level looks the same to me (although it is difficult to compare if your'e looking at 100% level of pictures taken at ISO 102400 and one at 25600 bumped 2 stops...)
BUT the 102400 has definitely less chroma noise, is it possible for canon to do some chrome noise reduction BEFORE the raw files are saved ?
How raw is raw ?


Marsu42

  • Contributor
  • Hero Member
  • *****
  • Posts: 1557
  • 66d + flashes
Re: 6D Dual Iso and more DR hack?
« Reply #65 on: January 21, 2014, 11:47:29 AM »
is it possible for canon to do some chrome noise reduction BEFORE the raw files are saved

I'm rather positive they do, you see that when comparing 5d3 & 6d samples - at most iso settings, the 6d files magically have less chroma noise than 5d3, but about the same luma noise. Some test also indicate that the 6d files are a bit less sharp than 5d3 w/o nr, so 1+1 = forced noise reduction in raw.

ilguercio

  • Hero Member
  • *****
  • Posts: 845
Re: 6D Dual Iso and more DR hack?
« Reply #66 on: January 21, 2014, 12:10:38 PM »
No raw file is REALLY raw.
Canon EOS 6D, 60D, 50D.
Sigma 70-200 EX OS HSM, Sigma 70-200 Apo EX HSM, Samyang 14 2.8, Samyang 35 1.4, Samyang 85 1.4.
Proud supporter of Magic Lantern.

Levas

  • Contributor
  • Hero Member
  • *****
  • Posts: 1741
  • 6d - Nightly build user

a1ex

  • Administrator
  • Hero Member
  • *****
  • Posts: 12564
Re: 6D Dual Iso and more DR hack?
« Reply #68 on: January 21, 2014, 03:30:41 PM »
Blind test (though it's really easy to cheat). Which is which?


Code: [Select]
ufraw-batch --exposure=4 6400.CR2
ufraw-batch --exposure=3 12800.CR2
ufraw-batch --exposure=2 25600.CR2

My .ufrawrc (so you can check the other settings and reproduce the results).

In real shooting, also consider how many highlights you have to throw away.

Audionut

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 3657
  • Blunt and to the point
Re: 6D Dual Iso and more DR hack?
« Reply #69 on: January 21, 2014, 04:07:04 PM »
Audionut is challenging it, so we don't have a final word on this.

I am?  I corrected myself in the ADTG thread.  On the 5D3, ISO 3200 is probably the last useful ISO.  I've posted a few examples now that show this. 

If you mean that last data sample of mine on saturate offset, I'm not confident either way, just that the data was showing strange results.

---------------------------------------------------------------------

If that last 0.1-0.2 EV of shadow detail is more important then 1EV of highlight detail, you may benefit from ISO 6400 vs ISO 3200.  And while the data suggests that ML ISO 6400 can give 9.1-9.2 EV of dynamic range, it does not consider the other sources of noise inherent in digital photography.  Bear in mind that the dynamic range data provided by most sources (including ML displays), is basing this figure on the difference between the maximum saturation level (white level) of the signal being captured and the noise floor.  It doesn't care how noisy the signal is between these 2 points.  This is where SNR curves are useful, as they display the SNR (image quality) through the entire exposure.  A general assumption for usable dynamic range, where the shadows aren't concealed by an excessive amount of noise, is to subtract 2EV from rated values (and this is subject to processing techniques and viewer tolerance on image noise).  If we apply this to the data we have for ISO 6400 on the 5D3, we are now left with around 7EV of useful data.  Suddenly that 1EV of highlight data that is getting thrown out when boosting ISO another stop (ISO 3200 vs ISO 6400 in this example), might actually be useful.  We've got 8EV of usable dynamic range with ISO 3200 vs 7.1EV of useful dynamic range with ISO 6400, and we haven't even considered the noisiest source in the signal yet, the shot noise.

At these low light levels (where ISO 3200/6400 is exposed correctly), the dominant noise source is the light itself (shot noise).  This noise in our images is controlled entirely on the number of photons (the amount of light) hitting the sensor.  As I like to point out at every opportunity, exposure (light hitting the sensor) is only controlled by lens diameter, shutter and aperture.  ISO does not control the light hitting the sensor.  Bumping ISO does not effect the shot noise of the image, period.

Analog ISO (voltage gain) is useful for boosting the the signal from the sensor.  The voltage gain is applied at the sensor.  So all those little bits of electronics further down the chain (ADC, DAC, etc), that have their own inherent Signal to Noise ratio, receive a full signal (from the sensor), and retain their full SNR capability.

Analog ISO actually reduces the noise from the camera electronics by boosting the signal through all of the remaining electronics and increasing the sensitivity of the amplifier*.  Random noise and Fixed Pattern Noise (banding noise), are reduced with increasing ISO.  The apparent noise increase with increasing ISO is that pesky shot noise that ISO does not control.

edit:  Readout noise is also increased with gain, but is also dominated by shot noise at low exposures.

The reason why we gain any improvement at all right near the noise floor for increasing ISO, where our images are shot noise limited, is because the camera electronics are still dominating the total noise near the noise floor.

*Note:  Rodger Clark specifically states that ISO does not increase the sensitivity.  He is referring to the sensitivity of the sensor.

-------------------------------------------------------


If you want to conduct your own testing, I would suggest that you expose your minimum test ISO at maximum saturation.  This ensures that the base line exposure contains the lowest amount of shot noise.  In this way, your testing procedure contains controlled shot noise for the tests. *see notes below

Remember, if you have to reduce exposure when increasing ISO (because you're tossing away 1EV of highlight data with every stop), you increase the shot noise with the exposure adjustment, and ISO does not reduce it.

Throw in tonal range with exposed bit depth, and you're on your own!

*Note:  You should not change exposure settings with increasing ISO.  We know the highlights will get clipped by 1EV, it's the shadow detail that important in this test.

Levas

  • Contributor
  • Hero Member
  • *****
  • Posts: 1741
  • 6d - Nightly build user
Re: 6D Dual Iso and more DR hack?
« Reply #70 on: January 21, 2014, 04:13:35 PM »
Blind test (though it's really easy to cheat). Which is which?

ooh, challenging.
After ten minutes of pixel peeping to the three 100% crops...
The first one is the most corrected with exposure (it looks more greenish then the other ones) so iso 6400
The middle one has the most evenly blue and red chroma in it, I would say untouched exposure, iso 25600
The last one is a little more greenish and has less red chroma, iso 12800.

BUT I wouldn't even bet 10 dollar on it  ;D
These differences are hardly noticeable at all...

a1ex

  • Administrator
  • Hero Member
  • *****
  • Posts: 12564
Re: 6D Dual Iso and more DR hack?
« Reply #71 on: January 21, 2014, 04:37:35 PM »
Left 12800, middle 6400, right 25600. You can check it by matching the alignment between images with the raw filenames.

I've posted it on Twitter too, and one guy got it right: https://twitter.com/autoexec_bin/status/425639803510484993

Now draw your own conclusions. If both 6400 and 25600 are nearly the same in shadows, and one of them has a 2-stop advantage in highlights, which one would you choose?

Levas

  • Contributor
  • Hero Member
  • *****
  • Posts: 1741
  • 6d - Nightly build user
Re: 6D Dual Iso and more DR hack?
« Reply #72 on: January 21, 2014, 05:48:20 PM »
I'm convinced.

Foolish me, buying a 6d thinking that I could take pictures at a "real" iso of 25600 and make incredible time lapses of stars in the sky.
Guess we won't go higher then 6400 anymore...

And probably the same for raw video, better to go 6400 at max ?

The twitter reactions are fun, you didn't tell them you pushed the 6400 iso 2 stops and 12800 iso 1 stop, they have no clue why iso 6400 looks that terrible  ;D

a1ex

  • Administrator
  • Hero Member
  • *****
  • Posts: 12564
Re: 6D Dual Iso and more DR hack?
« Reply #73 on: January 21, 2014, 05:51:57 PM »
and make incredible time lapses of stars in the sky.

Well, just look at what dmilligan is doing with a 1100D: www.magiclantern.fm/forum/index.php?topic=9860

Levas

  • Contributor
  • Hero Member
  • *****
  • Posts: 1741
  • 6d - Nightly build user
Re: 6D Dual Iso and more DR hack?
« Reply #74 on: January 21, 2014, 07:32:32 PM »
Well, just look at what dmilligan is doing with a 1100D: www.magiclantern.fm/forum/index.php?topic=9860

Says in his description that he uses a 60Da, but nonetheless, I know what the small body's are capable off.
Had a 1000d for years. Made many time lapses with it, wasn't afraid to use his highest iso (an incredible 1600 8)).
Cropping the images 3840 by 2160 pixels and then downscale to 1920 by 1080, little frame blending with the resulting videoclips and most of the noise was gone.
But couldn't live with the fact that the 1000d did not have magic lantern support... ::)
And of course I always dreamed off Full frame and there was the canon 6d!

Silly enough I've shot more raw video with it, then taking pictures  ::)

But if the iso's above 6400 are indeed fake (which seems to be the case), I'd rather liked it if canon called them H1, H2, H3 and H4. Just so we know there's some image trickery going on.