Is the E-M5 sensor response nonlinear?

[Iliah Borg]

But if looking at the 'SNR' ( or 'G2dev') values in column 2, then I don't see any tendency to a lower increase in the highlights than in the midtones.

You can see it does not fit the model. Please re-read on photon noise, its dominance in midtones and highlights, Poisson distribution, and, say, methods used to determine unity gain, as those methods explain the ratio of the signal to sigma^2.

Yes, I misunderstood.

My attempt to make it more clear was at http://forums.dpreview.com/forums/read.asp?forum=1041&message=42031320

I assumed (reasonably, I think) that the "SNR values" you were referring to actually were in the chart.

I referred to the fact that the last column (sigma^2) shows that the previous one (sigma) does not fit the model, and thus SNR does not fit the model.

We have nearly linear output with only SNR at highlights being lower (worse) than expected; and the un-fitness progresses from midtones up.

--
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http://www.RawDigger.com/

 

[Iliah Borg]

I just caught you with your pants down again.

Look into the mirror

--
http://www.libraw.org/
http://www.RawDigger.com/

 

[Anders W]

I just caught you with your pants down again.

Look into the mirror

In case you didn't know, this is a mirrorless forum.

 

[Iliah Borg]

I just caught you with your pants down again.

Look into the mirror

In case you didn't know, this is a mirrorless forum.

That explains it all. You are a joke.

--
http://www.libraw.org/
http://www.RawDigger.com/

 

[Anders W]

But if looking at the 'SNR' ( or 'G2dev') values in column 2, then I don't see any tendency to a lower increase in the highlights than in the midtones.

You can see it does not fit the model. Please re-read on photon noise, its dominance in midtones and highlights, Poisson distribution, and, say, methods used to determine unity gain, as those methods explain the ratio of the signal to sigma^2.

Yes, I misunderstood.

My attempt to make it more clear was at http://forums.dpreview.com/forums/read.asp?forum=1041&message=42031320

I assumed (reasonably, I think) that the "SNR values" you were referring to actually were in the chart.

I referred to the fact that the last column (sigma^2) shows that the previous one (sigma) does not fit the model, and thus SNR does not fit the model.

We have nearly linear output with only SNR at highlights being lower (worse) than expected; and the un-fitness progresses from midtones up.

This claim about nonlinearity is based on assumptions that are unlikely to be perfectly met and likely to bias the results in favor of your own hypothesis. Further, and more importantly, the SNR increases monotonically all the way up to the brightest patch, which is what we need to know in order to take proper advantage of the sensor.

 

[Anders W]

I just caught you with your pants down again.

Look into the mirror

In case you didn't know, this is a mirrorless forum.

That explains it all. You are a joke.

Never confuse the producer with the product.

 

[Great Bustard]

I just caught you with your pants down again.

Look into the mirror

In case you didn't know, this is a mirrorless forum.

That explains it all. You are a joke.

I've only followed the "discussion" in bits and pieces, but that (and other posts like it) are rather out-of-line. Anders' response was pretty funny (really funny, actually), and your retort is really quite boorish.

I consider you, Anders, and Bob to be among the most knowledgable people on DPR. Surely, disagreements can happen, and most certainly misinterpretations, but even so, the most knowledgable can be wrong on occasion.

So, please, either be informative or be civil -- I look to other posters for "entertainment".

 

[Anders W]

basically nobody knows whether Iliah is really smart or just really arrogant.

That is not an exclusive disjunction.

In my experience, it is. None of the really smart people I have encountered are arrogant. They don't need to.

 

[Iliah Borg]

disagreements can happen,

When the tread starts with distorting my words right to the point when the meaning is the contrary it is not a disagreement. It is a joke.

--
http://www.libraw.org/
http://www.RawDigger.com/

 

[Great Bustard]

disagreements can happen,

When the tread starts with distorting my words right to the point when the meaning is the contrary it is not a disagreement. It is a joke.

OK, like I said, I haven't followed it all except in bits and pieces. But I rather think that what you call "distortion" is more likely a matter of "misinterpretation". Anders, like I said, is a stand-up guy from all I've seen from him (and, yes, he and I have had disagreements, but I still have nothing but the highest respect for him).

 

[Iliah Borg]

But if looking at the 'SNR' ( or 'G2dev') values in column 2, then I don't see any tendency to a lower increase in the highlights than in the midtones.

You can see it does not fit the model. Please re-read on photon noise, its dominance in midtones and highlights, Poisson distribution, and, say, methods used to determine unity gain, as those methods explain the ratio of the signal to sigma^2.

Yes, I misunderstood.

My attempt to make it more clear was at http://forums.dpreview.com/forums/read.asp?forum=1041&message=42031320

I assumed (reasonably, I think) that the "SNR values" you were referring to actually were in the chart.

I referred to the fact that the last column (sigma^2) shows that the previous one (sigma) does not fit the model, and thus SNR does not fit the model.

We have nearly linear output with only SNR at highlights being lower (worse) than expected; and the un-fitness progresses from midtones up.

This claim about nonlinearity is based on assumptions that are unlikely to be perfectly met and likely to bias the results in favor of your own hypothesis. Further, and more importantly, the SNR increases monotonically all the way up to the brightest patch, which is what we need to know in order to take proper advantage of the sensor.

Somebody who did not know a day ago that all sensors are non-linear; and somebody who does not see the difference between non-linear encoding and natural non-linearity of response is talking

--
http://www.libraw.org/
http://www.RawDigger.com/

 

[Anders W]

On a side note, fools are not qualified to make judgements on the foolishness of others.

Correct. But some fools are not capable of fully appreciating their own foolishness, which presumably explains why you keep making this mistake.

Of course I do not expect you to understand that, but maybe you can at least practice that simple rule?

Unlike you, I accept the conclusion only when the premise is valid.

Anders, you are generally a sensible fellow. Just don't let the adrenalin of 'entertainment' lead you into making a fool of yourself.

I am actually moderately entertained by the "exchange" (if you can call it that) with Iliah.

If entertainment is what you are after, there are more productive sources. With Iliah you end up with the bruises to show for it.

And in precisely what sense do you think I am making a fool of myself?

By engaging in 'entertainment' when there is knowledge to be gained. It's easy to do. You're convinced you're right, haven't quite got the supporting evidence or argument, come across someone who disagrees in a supercilious way that dents your ego a bit, and you end up taking wrong turnings in your riposte. Done it myself, many times. Here's a recent example:
http://forums.dpreview.com/forums/read.asp?forum=1018&message=41982258

I was right in this case, but went down a great big blind alley before I took the trouble to sit down, work it out and get to the heart of why he was wrong.

You won't beat Iliah in one of these exchanges even in one of the rare cases where he is wrong - let alone in this case, when he is right.

In precisely what way do you think he is right?

He is right about non-linearity of the sensor (including the pixel SF) close to saturation. He's right that raw 'saturation' is commonly well short of pixel 'saturation'. He's also very probably right (though I don't have any information of my own) that manufacturers are using non-linear coding to re-linearise sensor response (he gave the example of the D4).

AFAIK, I haven't made any claim to the contrary.

I can't remember that there were any other substantive issues, though once you get into 'entertainment' those issues start to get lost.

Look at my posts towards the end of this thread for further information on what I have in mind.

Iliah made a claim which I proved wrong.

Just backtracked through the thread. Can't see it. Once you get into 'entertainment' self perception of proof starts to get lost. Proof gives way to 'that showed him'.

See previous comment.

I have invited him to perform a better experiment and a better analysis that proves me wrong. He hasn't been able or willing to do that. End of story.

And yet, he is right, and you know that he does have the experiment and analysis to back up what he says. He's just going to make you get there for yourself. Frustrating, isn't it?

I suggest you take a deep breath, forget the entertainment for a while, and try to reason out what he's saying.

As I said, this thread is not particularly "entertaining" to me in the sense you have in mind.

If he has something to say beyond semi-comprehensible one-liners, I'd be happy to listen.

Iliah's pedagogic style. Doesn't lecture, just drops you cryptic one liners that you need to follow and dig under to do the learning for yourself.

I'd call it Iliah's inability to communicate a defect rather than a style.

Since my pedagogic style is more of the lecturing variety, and that upsets people too, I wouldn't be one to say which causes more resentment. But the underlying point is the same, people who resent being taught don't learn.

As I have demonstrated on many occasions, I have nothing against learning from you or other knowledgeable people on this forum.

I have never found reason to place much confidence in people who are unable or unwilling to develop their thought in a paragraph or two of ordinary text meant to convince the other party rather than FUD him/her into silence by vague references to this or that technicality without even bothering to spell out their relevance.

And generally that test will separate out the BS merchants from the real deal, but in this case, it hasn't.

Not so sure about that.