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Messages - sarangiman

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1
LTRLI:

Do you use Windows or Mac? If the latter - how do you even profile the wide-gamut Dell displays? My understanding was that their internal LUTs are only addressable by the included software, which only runs on Windows.

Any other third-part software (like the excellent dispcalGUI/Argyll) would, AFAIK, not have access to the internal LUTs, which means it'll be making corrections to the 8-bit data, which is, of course, not so desirable (not when you have internal LUTs anyway).

I wish more displays would have user-addressable LUTs - please correct me if I'm wrong though re: 3rd party software accessing the LUTs of the Dell displays.

Also - has anyone *confirmed* that the Retina iMac is *not* wide-gamut? If they're using similar panels to the Dell 5K monitor, how is there a difference in gamut? Is it perhaps the same hardware but with a forced, limited gamut mode?

To be honest, I'm not that surprised Apple generally chooses to go for more standard gamut monitors, although I'm a big fan of wide gamut. The problem of the wide gamut displays is that a lot of times you end up editing in colors that aren't in sRGB (especially when working from Raw), that don't then convert well to sRGB for web output. So you get this massive color change to oranges/reds especially sometimes when you convert to sRGB for web.

Also, profiling wide-gamut displays isn't so easy - if you use standard colorimeters, they need to have color correction matrices generated by a spectrophotometer to deal with the primaries of wide gamut displays (standard colorimeters expect different RGB primaries, and so can create very inaccurate profiles when profiling a wide gamut monitor). Or you *have* to use a spectrophotometer for profiling, which to me is not so ideal since they don't 'see' darks very well (unless the software is intelligent enough to increase the integration time during profiling for dark colors).

In fact, I've found that to make the best profiles for my Dell U2711, I've had to use a ColorMunki to create a color correction matrix for my i1 colorimeter, which I then use to actually profile (dispcalGUI lets you do all this). Otherwise, upping the integration times when profiling w/ the ColorMunki means it takes *forever* to make a profile. Whereas w/ the correction matrix, you just do that once, then every future profile generation step is quick w/ the i1 colorimeter.

I've verified that the results from ColorMunki+long integration times ends up creating roughly the same profile as the i1 colorimeter + the ColorMunki generated correction matrix.

How have others gotten around this profiling issue?

Apologies if I went a bit OT there...

2
Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 10:17:36 PM »
Yes, you guys call 'useable toanlity' 'sensor DR', I have never understood that to be a way of stating 'photographic DR', I only know and understand the difference in recordable luminosity values.

Again, I think this is an area where the technologists have confounded and annoyed the photographers. When I, and millions of others, think of photographic DR we are thinking about the difference in scene luminosity we can actually record, not the point at which the dark tones become noisy. Replicating that capability on devices with a much smaller luminosity range is not and never has been the question.

So who has some RAW step wedge files to upload?

But 'the difference in scene luminosity we can actually record' is exactly what DxO is measuring. Because their DR is defined as the brightest bright vs. the darkest dark that is not lost in noise. 'Not lost in noise' is where SNR = 1, according to DxO. This is known as 'engineering dynamic range'.

Would you like DxO's lower cutoff to be higher, since you can't use SNR = 1 (where tones are completely lost to noise)?

SNR = 1 is used as the lower cutoff b/c different folks could argue till the cows come home what SNR is usable.

If that's what bugs you, then use Bill Claff's excellent analyses, where he defines a 'photographic DR' using a higher SNR cutoff:

http://cl.ly/Y2gu/D810_vs_A7S-PixelLevel.png

The differences between cameras are still fairly similar to DxO's findings, but the absolute numbers are different. Higher SNR cutoffs on the low end tend to shrink the differences between cameras of the same sensor size. After a certain point, a higher SNR cutoff won't even distinguish between cameras of similar sensor sizes, b/c the lower SNR cutoff will be dominated by the effects of shot noise (which'll be similar between cameras of similar sensor sizes), so that's not helpful either.

But Bill Claff's results vs. DxO's normalized results is just half a stop different (2.5 EV vs 3 EV) for the D810 vs. 5D3 for example. Not exactly earth shattering.

Is that what this entire debate, and all this arguing, is actually about in the end?

3
Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 10:04:21 PM »
actually, I think I can see PBD's point of view on this - you can't average a bunch of zeros and get a lower zero.
but you can average  bunch of slightly above zero shades+noise which has the effect of increasing effective DR because now there's more useable tonality.

I think the difference in arguments is the threshold chosen for the base
 numerical 0 = black vs SNR=1 = black.

Yes, 'black' is defined by your cutoff. For a more reasonable SNR threshold of 2 or 3 (or corrected for COC as Bill Claff does), 'black' is actually a significantly higher number than 0 or 1. And that's where it's conceptually easier to see what downsampling can do.

So maybe the breakdown in understanding occurs b/c DxO keeps quoting numbers in and around the bit-depth of the ADC.

The principle of downsampling helping tones become usable is not hard to see. Check out the pixel-level noise of the D810 vs the A7s in DPR's studio scene here at ISO 12.8k:

http://www.dpreview.com/reviews/image-comparison/fullscreen?attr18=lowlight&attr13_0=nikon_d810&attr13_1=sony_a7s&attr13_2=sony_a7r&attr13_3=sony_a7s&attr15_0=raw&attr15_1=raw&attr15_2=raw&attr15_3=raw&attr16_0=12800&attr16_1=12800&attr16_2=12800&attr16_3=12800&normalization=full&widget=1&x=-0.33073366646429747&y=0.23770150083379657

Not very usable, right?

Now look at it normalized:

http://www.dpreview.com/reviews/image-comparison/fullscreen?attr18=lowlight&attr13_0=nikon_d810&attr13_1=sony_a7s&attr13_2=sony_a7r&attr13_3=sony_a7s&attr15_0=raw&attr15_1=raw&attr15_2=raw&attr15_3=raw&attr16_0=12800&attr16_1=12800&attr16_2=12800&attr16_3=12800&normalization=full&widget=1&x=-0.33073366646429747&y=0.23770150083379657

Look at the stripes in the black jacket? Suddenly you can see them, b/c they're not swamped in noise. Suddenly the become more usable. Those were dark tones not very usable at 36MP, but now usable at 8MP. B/c after pixel averaging, the SNR of those tones went up, above the arbitrary threshold I selected when I said that that jacket was 'not usable' at the pixel-level.

Here it is again as screenshots:

Pixel-level (not how you can't even make out the vertical stripes in the black jacket on the rightmost Beatle, b/c they're lost in noise):


Normalized (you can now make out the stripes, just like you can on the A7S):

4
Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 09:53:21 PM »
actually, I think I can see PBD's point of view on this - you can't average a bunch of zeros and get a lower zero.
but you can average  bunch of slightly above zero shades+noise which has the effect of increasing effective DR because now there's more useable tonality.

I think the difference in arguments is the threshold chosen for the base
 numerical 0 = black vs SNR=1 = black.

Yes, PBD's question is very valid, and interesting, and I can totally see his confusion. The problems comes in the actual numbers. I'm not absolutely certain I believe the absolute DxO numbers - as in what's actually usable by a photographer. SNR=1 data is not usable by a photographer.

But, I couldn't say it better Aglet - exactly, it's that other (e.g. single digit) tones become more usable upon downsampling.

5
Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 09:44:38 PM »
What it won't do is have a brighter bright or darker dark, and surely that is the measure of DR, not how many divisions that same range is divided into?

actually, it may be an oversimplification but yes, downsampling will give you darker dark tones as the noise (which lightens them) is averaged out.
Therefor, greater effective DR, when measured as the ratio of light/dark at some SNR limit.

Daniel already covered that point, and we all agree, some dark tones are liberated by noise mitigation, but that doesn't alter the fact that black and white still have the same luminance values.

Going back to my initial question, if a single pixel has a well capacity of 14 stops of DR recording capacity how can downsampling that give me a brighter or darker luminescence? If 0 equals black and white is 16,384 where is the extra capacity? What is being said is that a 'noisy' sensor can't record detail below 0-1,000 (for example) by comparison a 'clean' sensor can record greys in the 500-1000 range 'so it has more DR', I say not, I say the total range from black to white is still the same, the clean sensor has more tonality between black and white, but it doesn't have more luminosity range between black and white.

Maybe that is where the difference is, I and everybody since, ever, has equated photographic DR to the range of luminosity values and the sensor geeks insist on referring to it as levels of tonality.

I've already explained it, but it probably got lost in all the noise.

You've got it, pvd: "some dark tones are liberated by noise mitigation" --> exactly!

But then you said "but that doesn't alter the fact that black and white still have the same luminance values." That's where things are falling apart.

What is 'black'? There is no definition of 'black' other than 'signal at the noise floor'. Well if you've just brought signal above the noise floor by 'liberating them by noise mitigation', then they've just become usable tones. To see them, though, you need your output device to bring them up to a usable level. Today's monitors and prints don't generally do that, which is why we push shadows --> essentially tone-mapping.

And I don't know how clearer I could make it than when I showed the D800 vs D600 Screen vs Print DR curves. No sensible person testing the two cameras would give the D600 more DR, which is what the 'screen', pixel-level analysis indicates. The normalized analysis indicates they're pretty much the same - which is exactly what you'll find in the real-world if you try and shoot high DR landscapes or try to do shadow pushing from equally exposed files.

Please tell me it makes sense now?

6
Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 09:40:00 PM »
Quote
Quote
In all examples to date the actual total DR difference is very small. Noise is very different which of course affects latitude and what is acceptable when exercising said latitude on the shadow side.

Very small?

Yes. Canon sensors are not blocking up a lot sooner then an Exmor sensor (though they do block up a little sooner). But the noise makes detail in the lowest tones unacceptable, when pushed higher on the scale, for most photographic purposes.

So you'd prefer words like 'little' or 'very small' compared to quantitative numbers like 2.5 EV difference, etc.

Ok, now that was totally worth having a conversation about. I'm glad I now know that when one says that you can pull tones that received 10x less exposure (an 'order of magnitude' to 'scientists', but who understands them anyway), you consider that 'small' or 'little'. That was so worth arguing over.

Quote
Yes, let's refer to Ansel Adams to talk about sensor DR. Because sensors totally existed back then.

They did. They were called "film."

... which required a slightly different method to analyze DR back then than the best method to measure DR of sensors now. You measured film densities, when and where film could no longer distinguish tones. And that's exactly what SNR analyses do now, even more rigorously. But the techniques are subtly different. As they should be, separated decades apart.

What's your point?

Quote
But the reality of it is that you measure dynamic range of sensors in a different way.

The definition and model of photographic dynamic range does not change based on capture medium.

I agree with your statement here. I also agree with my previous statement you quoted. They're not mutually exclusive. You're still not getting it.

I give up; this is like knocking one's head against the wall. I'm not continuing a conversation with someone who finds it fun to knock science, even though science was used to make his camera, and evaluate it as well.

There are those here actually making valid points and asking valid questions; all you do is derail and misinform.

7
Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 07:37:53 PM »
Perhaps a good exercise would be for you to actually measure DR by doing some SNR analyses from wedge shots yourself before you so confidently talk about this stuff? I'm being serious, not trying to be rude. You seem to almost have a grasp of this stuff, and feel you would finally 'get it' if you did some analyses yourself.

I'm being serious when I say that every single person at DxO needs to shoot a transmission step wedge and then print it at different sizes and observe (as opposed to running it through a black box algorithm they designed before trying this test).

It would clarify some things for them, and we might end up with a usable model of DR from their existing database of measurements.

Wait, what? How do you print it? How do you process the Raw? What's your methodology? How do you fit the enormous capture DR of a modern sensor into the tiny DR of current output media to then get an idea of the capture device's DR?

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Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 07:32:03 PM »
Quote
You're not even looking at the darker patches of the wedge, are you?

Of course I have.

How? How are you looking at patch 41?

In all examples to date the actual total DR difference is very small. Noise is very different which of course affects latitude and what is acceptable when exercising said latitude on the shadow side.

Very small? Do some digging. Seriously. This is no longer up for debate. Noise is different? You do know that noise is intimately linked to sensor dynamic range...?

Quote
How, prey, do photographers measure it, then? Please, enlighten us.

http://www.amazon.com/Negative-Ansel-Adams-Photography-Book/dp/0821221868

Yes, let's refer to Ansel Adams to talk about sensor DR. Because sensors totally existed back then. And by the way, Ansel Adams was a smart dude who did a lot of experimenting ("science") to figure out how to get the most out of his medium. But the reality of it is that you measure dynamic range of sensors in a different way.

Quoting Ansel Adams is particularly ironic, given how scientific and quantitative he was.

I think I understand what the actual problem is. You're not actually talking about camera DR. You're talking about output DR - what you finally see on your print or monitor. Which is entirely different.

Until you understand even the basics of what we're talking about though, there's no point in continuing this conversation.

One thing's clear: it seems you don't understand what sensor dynamic range is, and sensor dynamic range is what dictates how much real world dynamic range a camera can capture.

Please stop knocking what you clearly don't understand.

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Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 07:15:06 PM »
And there it is...an appeal to authority. If you can't grasp logic 101 how can you grasp the difference I am trying to point out to you?

Oh, I see. I suppose we should appeal to... you?

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Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 07:14:22 PM »
What's grey? You know it depends on your monitor, right? Or your processing?

In this context? Recordable tones, which does not depend on a monitor.


How are you judging recordable tones?

Since you're not doing a statistical analysis, you must be using *something* to judge what you consider 'recordable tones'. How are you doing it?

Are you using your monitor? In which case it does depend on the monitor. And what you're doing to the Raw file.

Are you using a print? In which case it depends on your entire workflow and a whole bunch of other stuff.

This is why there's an actual, objective way of measuring DR. And you're totally ignoring and knocking it.

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Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 07:08:28 PM »
K, I'm with msm. I just give up. It's not about black squares turning grey. DR is measured from statistical analysis.

Photographers do not measure it this way. And it's not a simple matter of semantics because your "engineering DR" model fails to predict what photographers observe the field.

DxO's definition of DR is correct.

Observation trumps theory. Every. Time.

Not when you're observing completely wrong.

You're not even looking at the darker patches of the wedge, are you? This is getting comical. What are you looking at? The JPEGs on your monitor? The Raw conversion? Just a straight linear output to your monitor or print? No pushing the shadows? No statistical analyses? And you think this is a measure of DR??

Don't bring Ansel Adams into this. Yes, how you measure DR has changed since the days of film, imagine that!

Many photographers have already observed the stops upon stops of difference in DR.

How, prey, do photographers measure it, then? Please, enlighten us. Like I said, it's *you* who has something to prove, not the image scientists at DxO, and not the countless photographers who've themselves showed (via actual pictures) the drastic differences in DR - exactly as DxO data predicts.

I showed this years ago; some people just didn't want to accept it. I believe you were one of them.

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Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 06:35:09 PM »
dtaylor: Also, by calling DxO wrong consistently, you're arguing that you're more right than a bunch of image scientists. You have a lot to prove there, my friend.

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Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 06:32:29 PM »
Note: noise can be so severe that it obscures the last patch or two of gray in such a test, whereby downsampling would reveal them. But there's not any where near that much noise at base ISO on any of these cameras.

What's grey? You know it depends on your monitor, right? Or your processing?

If you've actually shot a 42 step 13 stop Stouffer wedge, you'd know that patches 32 - 41 are swamped in noise with a Canon DSLR at base ISO.

So what do you mean there's not much noise at base ISO?

You do realize you have to push the exposure to 'see' those higher number patches, right? That with your limited output device (your monitor), you can't see them until you push them?

Are you not even looking at them pushed? Is that why you think there's no noise?

Are you doing any statistical analyses? If you're not, you're not actually measuring DR. Period.

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Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 06:28:17 PM »

Quote
Clearly you've never shot an actual 13 stop wedge with a Canon DSLR,

Clearly you never have if you think black squares turn gray with downsampling.

Quote
Clearly you've never shot an actual 13 stop wedge with a Canon DSLR, if you haven't seen any unusable patches with so much noise that SNR drops below 1 or 2.

LOL! The patches are patches for a reason, and the test is not subject to your opinion of "pixel level" usability.

K, I'm with msm. I just give up. It's not about black squares turning grey. DR is measured from statistical analysis.

DxO's definition of DR is correct. Whether or not you agree with their SNR cutoff is a different story.

Your talk of black vs. grey is completely irrelevant.

Don't confuse sensor DR with the combined DR of your input + output devices.

Just stop. Stop completely misinforming people.

As long as your sensor has a linear response, DR is the ratio of the brightest tone to the darkest tone above SNR = your cutoff threshold.

That's it. That simple.

15
Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 05:14:33 PM »
You are confusing signal (tone variations across 2D space) with dynamic range (the brightest and darkest tones that can be recorded). So is DxO.

Down sampling lets you confidently say that yes, in this tiny region of 2D space we really did detect a tone variation and not just noise fluctuations. It does not mean you recorded a lower min tone.

No, again, the definition of engineering DR is the range of tones between clipping and where signal is swamped in noise (SNR = 1).

Downsampling increases SNR, which makes darker tones more usable.

Whether or the sensor accurately recorded the tone or not - that's a measure of sensor linearity, which you can also measure in SNR analyses. I do, and so does DxO actually.

If there's enough noise at the lower end, it'll raise your average signal, and your sensor will deviate from linearity. This happens pretty early on (on the low end) for Canon. It's another way you can get an idea of DR, but I haven't found it an acceptable standard for DR measurement yet (i.e. 'where does it deviate from linearity?' as the lower cutoff, as opposed to SNR = 1 as the lower cutoff).

In the transmission step wedge example I always throw out the signal...the squares in the wedge...is so large to begin with that only extreme noise could obscure it. Therefore you get a true idea of the range of tones that can be recorded.

Wait, what? How do you do a SNR analysis - which is the proper way to measure DR quantitatively - if you throw away the signal??

What are you doing?

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