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Author Topic: Dynamic range limitations due to glare and flare  (Read 18646 times)

Guillermo Luijk

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Re: Dynamic range limitations due to glare and flare
« Reply #20 on: July 21, 2015, 11:20:33 am »

No, it does not contain details. Those are some crude changes in brightness, nothing natural, and the overall contrast is not of a photographic image. Even on your "12 stops: indoor scene" the view from the window in not even close to a natural view. Such HDR is in the forensic processing domain. And again, I would be very interested to see the scene measurements because I think only such measurements may really put a number onto the scenes you are shooting.

You again focus on the applied tone mapping Iliah, but my lack of skills in HDR processing is irrelevant for what I'm demonstrating: capturing more than 11 stops is nothing veiling glare will prevent as a general rule. Tons of real world scenes with higher DR can be properly captured with just a couple of shots, and glare is not an issue on them.

You can download the RAW file and see for yourself. There is nothing unexpected or unnatural when you process it linearly with 0 adjustments, just the usual dull image one gets before saturation and tone curve are applied:




Regards


« Last Edit: July 21, 2015, 11:25:31 am by Guillermo Luijk »
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Iliah

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Re: Dynamic range limitations due to glare and flare
« Reply #21 on: July 21, 2015, 11:37:31 am »

Sorry, but it is the wrong contrast on the crop. It is washed out.
Now, the things start with metering. You suggest the scene is 12 stops wide, based on the raw data. My question is how wide it is based on direct measurements. Clear sky through a window is 14 EV, office is about 8 EV with artificial light only. Question is - how wide is the given scene?
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Guillermo Luijk

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Re: Dynamic range limitations due to glare and flare
« Reply #22 on: July 21, 2015, 12:07:50 pm »

At least 12 stops, i.e. larger than your 11 stops figure. Veiling glare is not an issue here, full stop. Photographers take pictures, they are not forensic analyzers.

Iliah

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Re: Dynamic range limitations due to glare and flare
« Reply #23 on: July 21, 2015, 12:18:40 pm »

At least 12 stops, i.e. larger than your 11 stops figure. Veiling glare is not an issue here, full stop. Photographers take pictures, they are not forensic analyzers.

I do not see 12 stops here, and I see an issue with haze and lost contrast. This is going nowhere unless you have an accurate set of measurements, but the raw histogram shows nothing in the green channel past -8EV, and pretty much nothing past -7 2/3 EV where the noise bell dominates.
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EricV

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Re: Dynamic range limitations due to glare and flare
« Reply #24 on: July 21, 2015, 12:31:19 pm »

I asked you, "how did you determine the original scene had 16 EV of range?" - that is, what is the map of the spotmeter readings?
The raw histogram from the actual photograph(s) is absolute proof that the original scene had at least as much dynamic range as claimed.  A meter reading could show that the true dynamic range was even greater.  But the dynamic range was certainly not less than what was actually recorded by the camera.
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AlterEgo

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Re: Dynamic range limitations due to glare and flare
« Reply #25 on: July 21, 2015, 12:39:44 pm »

Such HDR is in the forensic processing domain.
even so it still means that Guillermo managed to have greater DR captured w/ whatever glare/flare happened... just like a difference between "PDR" and "engineering DR" from DxO... DxO still makes their numbers from some raw data, even in some artificial lab conditions... not from some math model of the sensor, no ?
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AlterEgo

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Re: Dynamic range limitations due to glare and flare
« Reply #26 on: July 21, 2015, 12:41:17 pm »

The raw histogram from the actual photograph(s)
the only posted raw was a synthetic one, was it not ? I am not saying that it was made from blended original raws in some creative manner though.
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Iliah

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Re: Dynamic range limitations due to glare and flare
« Reply #27 on: July 21, 2015, 12:46:26 pm »

The raw histogram from the actual photograph(s) is absolute proof that the original scene had at least as much dynamic range as claimed.  A meter reading could show that the true dynamic range was even greater.  But the dynamic range was certainly not less than what was actually recorded by the camera.

> the dynamic range was certainly not less than what was actually recorded by the camera.
There are several reasons why one can't decide on the dynamic range of the scene based on raw files, and one of those is noise, the other is veiling glare. In a word, no measurements from scene taken and mapped over the shot - no way to know the dynamic range of the scene.

If  the HDR raw is a linear superimpose the total DR in HDR file it is an accurate measure of the sum of the dynamic ranges of the source raw files. That means the recording contains less than 12 stops; and if you insist the recording is the accurate representation of the luminocities in the scene, so is the scene - less than 12 stops.

Put a Q13 in the scene, and we will see how the contrast is changed.

Kodak Q13 target, semi-gloss, shot with Df at ISO 100 with -1 2/3 EV, which means the black is 8 stops down from clipping, normal diffused studio light setup, even light from high-grade sources.

First column is the data for Y on Q13, measured with Spectrolino, range 0..100, and normalized to exposure difference (before normalization the brightest patch was 91.26); second column indicates the number of stops down from clipping; third column is shot data normalized to 100 (so it essentially also contains percent of gray); and the last column contains the deviation from linearity, also in stops.

Spectrolino_Y EV_down_from_clipping AsShot_Y Non-linearity(EV)

29.961 -1.739 29.990 0.00

22.903 -2.126 23.712 -0.05

18.090 -2.467 18.778 -0.05

14.331 -2.803 14.978 -0.06

11.307 -3.145 12.035 -0.09

8.969 -3.479 9.322 -0.06

7.180 -3.800 7.591 -0.08

5.647 -4.146 6.050 -0.10

4.495 -4.476 4.848 -0.11

3.641 -4.780 3.868 -0.09

2.886 -5.115 3.130 -0.12

2.311 -5.435 2.525 -0.13

1.839 -5.765 2.042 -0.15

1.468 -6.090 1.673 -0.19

1.202 -6.379 1.349 -0.17

0.965 -6.695 1.166 -0.27

0.798 -6.970 0.986 -0.31

0.607 -7.363 0.841 -0.47

0.545 -7.520 0.793 -0.54

0.417 -7.906 0.712 -0.77
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AlterEgo

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Re: Dynamic range limitations due to glare and flare
« Reply #28 on: July 21, 2015, 12:46:47 pm »

but the raw histogram shows nothing in the green channel past -8EV, and pretty much nothing past -7 2/3 EV where the noise bell dominates.

I used FRV and added 8 EV simulated exposure



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Iliah

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Re: Dynamic range limitations due to glare and flare
« Reply #29 on: July 21, 2015, 12:50:15 pm »

> Guillermo managed to have greater DR captured w/ whatever glare/flare happened

Well, when one starts to look at an image with the eyes of a photographer (or a demanding customer not interested in "modern art") he may want to reconsider "managed". The indoors scene is on the edge, while the toilet is well past usable.
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AlterEgo

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Re: Dynamic range limitations due to glare and flare
« Reply #30 on: July 21, 2015, 12:51:30 pm »

> Guillermo managed to have greater DR captured w/ whatever glare/flare happened
Well, when one starts to look at an image with the eyes of a photographer

that's not fair ! again - PhDR vs EnDR ... so fine print shall be added to any statements

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Iliah

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Re: Dynamic range limitations due to glare and flare
« Reply #31 on: July 21, 2015, 12:51:46 pm »

I used FRV and added 8 EV simulated exposure





And is it a photographic image? Does it contain something that can't be simply clipped?
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AlterEgo

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Re: Dynamic range limitations due to glare and flare
« Reply #32 on: July 21, 2015, 12:53:45 pm »

And is it a photographic image? Does it contain something that can't be simply clipped?
in the eye(s) of beholder... forensic/pixelpeeping folks are as good clientelle as anything else !
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Iliah

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Re: Dynamic range limitations due to glare and flare
« Reply #33 on: July 21, 2015, 12:58:34 pm »

that's not fair ! again - PhDR vs EnDR ... so fine print shall be added to any statements



2008 GoogleTech video of a talk by John McCann

https://youtu.be/ALfiTDYLtAQ

1 log unit is 3.3 EV.

and

http://mccannimaging.com/HDR/HDR_Papers.html
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BJL

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Dynamic range limitations due to glare and flare -- in a single exposure?
« Reply #34 on: July 21, 2015, 01:10:37 pm »

Guillermo and Illiah,

    if I undersigned the glare/flare/DR issue correctly, this DR limitation arises in a single capture, but can be overcome by taking several shots at different exposure levels and blending them.  Have I got that right?


P. S. No, I didn't!   I see now that once flare/glare from the brightest part of a scene is at a level of, say, 11 or 12 stops below, it will be so in all of the multiple frames used in HDR, all al will have equally veiled deep shadows.  Unless one does something extra like blocking out the brightest part of the scene (ND grad?) in some exposures used to blend.
« Last Edit: July 21, 2015, 04:07:38 pm by BJL »
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Iliah

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Guillermo and Illiah,

    if I undersigned the glare/flare/DR issue correctly, this DR limitation arises in a single capture, but can be overcome by taking several shots at different exposure levels and blending them.  Have I got that right?

Absolutely not. The limitation is with the system, before the image is captured, and the nature of that limitation comes from the dynamic range of the scene and the performance of the optical system. Increasing exposure, one gets to optical artifacts being more visible, that's all.
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AlterEgo

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    if I undersigned the glare/flare/DR issue correctly, this DR limitation arises in a single capture,
define single capture... what if I have a sensor with sensels individually controlled for exposure time and/or how translucent is the topping  on top of them ?
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EricV

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Re: Dynamic range limitations due to glare and flare
« Reply #37 on: July 21, 2015, 03:07:34 pm »

> the dynamic range was certainly not less than what was actually recorded by the camera.
There are several reasons why one can't decide on the dynamic range of the scene based on raw files, and one of those is noise, the other is veiling glare. In a word, no measurements from scene taken and mapped over the shot - no way to know the dynamic range of the scene.
Are you agreeing or disagreeing with the quoted statement?  I agree with you that one cannot determine the dynamic range of the scene from the raw files.  I assert that one can however set a lower limit on the dynamic range of the scene from the raw files.
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Iliah

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Re: Dynamic range limitations due to glare and flare
« Reply #38 on: July 21, 2015, 03:33:49 pm »

Are you agreeing or disagreeing with the quoted statement?  I agree with you that one cannot determine the dynamic range of the scene from the raw files.  I assert that one can however set a lower limit on the dynamic range of the scene from the raw files.
I disagree with your "certainly", because where there is noise, there is uncertainty.
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AlterEgo

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Re: Dynamic range limitations due to glare and flare
« Reply #39 on: July 21, 2015, 03:42:07 pm »

I disagree with your "certainly", because where there is noise, there is uncertainty.
the DR can be either greater or equal or smaller... noise can only reduce DR as recorded in raw data vs the original scene, no ? is there a situation when noise can increase the DR ?
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