Nerd Wars...Part 1

[chuxter]

Maybe because chuckup considers himself to be a pro.

Semi-pro would be accurate...or a pro-wannabe? ;-)

You should worry, from the title, he clearly intends there to be a part 2, maybe even 3, 4, 5....

Nah. There already was a part 2...it was my second post in this thread. I got carried away and wrote too many words and had to split it into 2 parts.

To answer the Q: It's here because 2am_strobist asked a question here and his thread was hijacked by Thomas (and others). It quickly maxed out. I started this thread here for exactly the reason that the original post had confused several Pros. I wanted to get some closure for them.

It really is the type of subject matter that should be on the Open Talk Forum.

--
Charlie Davis
Nikon 5700, Sony R1, Nikon D50, Nikon D300
HomePage: http://www.1derful.info
“...photography for and of itself – photographs taken
from the world as it is – are misunderstood as a
collection of random observations and lucky moments...
Paul Graham

 

[thomasnb]

It took some shots of some blossom in my garden to illustrate the point. Procedure:

1. Set the maximum exposure I could, which was f/8 (the max aperture of the lens), 1/250 (to avoid shake handheld at 175mm - just to note, the EXIF shown is wrong due to the 1.4x TC fitted).
2. Adjust the ISO until the meter is centred - e.g 'correct' exposure according to the camera, which turned out to be 400 ISO
3. Take two further shots at 800 and 1600 ISO without adjusting the exposure .

Here's the results. First ex-camera jpegs, without alteration.













Now the raws processed for the same output tonal range













Lastly 100% crops to judge the noise













Let you draw you own conclusions (made a bit more difficult as I didn't nail focus in the 800 ISO shot).

--
thomas

 

[thomasnb]

decide beforehand how big an exposure you can tolerate

I swear....... none of this makes much sense if any.

What is hard about the statement above? Please tell me what it is you're having difficulty with, and I'll try to reword it.

It seems as though you are trying to sell this as like you have reinvented the wheel. Expose to the right of the histogram and recover the highlights in PP at the lowest possible ISO. Hasn't this been always been the way ?

But that isn't what I'm saying. I'm saying decide beforehand how big an exposure you can tolerate then use that, and process for it.

And the samples you show won't convince anyone of the correctness of your technique is this is the best result you can show.

Those examples weren't intended to be the 'best result I can show'. All they were intended to show were that the effect of low lighting can be as easily achieved in processing without prejudicing the noise as would happen if you reduce the exposure to achieve it. I found the first shot I had suitable to illustrate that particular point and just processed it to suit very quickly as needed for the illustration. There's a limit to the time I'll spend preparing examples just for this forum.

--
thomas

 

[thomasnb]

Maybe because chuckup considers himself to be a pro.

Semi-pro would be accurate...or a pro-wannabe? ;-)

I'll remember that next time you go on one of your little tirades about what pro's want.

To answer the Q: It's here because 2am_strobist asked a question here and his thread was hijacked by Thomas (and others).

mainly hijacked by you (and others). I made a single clear post answering 2am_strobist's OP directly. That would have been it if you and your friends hadn't decided to pick apart every last thing I wrote, when they do that, I kind of have a right to respond, and I do.

It quickly maxed out. I started this thread here for exactly the reason that the original post had confused several Pros. I wanted to get some closure for them.

There you go, the wannabe talking for the pro's again. In any case, if you want 'closure' best not to engage in the tendentious flow of lies and misrepresentation that you have. It doesn't help clarify the issue, because when you lie about what I said, then I feel I have a right of response, so I do. Moreover, the lies just cloud the issue.

It really is the type of subject matter that should be on the Open Talk Forum.

I guess if the mods felt that way they would have moved it.
--
thomas

 

[Nick in Shanghai]

decide beforehand how big an exposure you can tolerate

What is hard about the statement above? Please tell me what it is you're having difficulty with, and I'll try to reword it.

Do these big exposures come in little or medium.........can I super size my big exposure ?

WTF is a big exposure ? In thirty plus years in photography I have never heard the term.

So Ms Leibovitz what kind of exposure did you shoot your iconic Rolling Stone cover of John and Yoko ?.............Oh, I used a big one. We thought about using a little one, but you know John's an ex Beatle and all, plus this was for a cover so we went with the big one.

 

[Nick in Shanghai]

Let you draw you own conclusions

Looking at the images labeled RAW and not the crops, you have a problem with the colour rendition and contrast at 800 and 1600 compared to the 400. When you correct those, then what happens to the test ?

--
Nick in Shanghai.

 

[thomasnb]

decide beforehand how big an exposure you can tolerate

What is hard about the statement above? Please tell me what it is you're having difficulty with, and I'll try to reword it.

Do these big exposures come in little or medium.........can I super size my big exposure ?

WTF is a big exposure ? In thirty plus years in photography I have never heard the term.

Exposure is the amount of light at the sensor, so a big exposure is one with a lot of light, either by dint of bright incident light, large aperture or long shutter speed. If you can think of a better term, I'd be grateful. The reason that people have difficulty with it is possibly because, like you, big (or large) exposure is a term they can't grasp.

So Ms Leibovitz what kind of exposure did you shoot your iconic Rolling Stone cover of John and Yoko ?.............Oh, I used a big one. We thought about using a little one, but you know John's an ex Beatle and all, plus this was for a cover so we went with the big one.

The technique doesn't apply really to film, because it doesn't have a linear characteristic to light.

--
thomas

 

[thomasnb]

Let you draw you own conclusions

Looking at the images labeled RAW and not the crops, you have a problem with the colour rendition and contrast at 800 and 1600 compared to the 400. When you correct those, then what happens to the test ?

I just did a straight forward conversion, scaled for the theoretical difference between ISO 400, 800 and 1600. Obvuiously, in real use you'd want to tweak colour and contrast for your needs. As you point out, in this conversion the contrast is higher than one would want in all of them, but I just went for a default tone map in each case. In any case, tweaking the colour and contrast isn't going to make a major difference to the noise.

--
thomas

 

[ejmartin]

On the DxO graphs (both the print and screen versions), the 800 ISO points are slightly below the "line". This indicates lower DR, which seems counter to the vast number of subjective opinions. Any thoughts?

The deviation is within the margin of error of the measurements. I would not give it significance in the absence of other evidence of something going on.

I noticed that you used a different expression, above. In the past, you confused Harry and others when you said the D300 wasn't "useful" above 800 ISO. Now you have a different way of expressing that...you said, 400 ISO was " the point of diminishing returns " for the D300. Hmmm...

I said ISO's above a certain point weren't "useful" because they didn't improve the S/N. We were talking about noise, weren't we? They might be useful for ancillary reasons, as DSPographer mentioned (not-too-dark review image in-camera, live view, etc; though all these could be fixed with better firmware); but not for improving noise performance.

And as I replied in another post, this does not mean the camera should not be used for low light photography or other situations where the exposure is low. It just means that the noise in the images obtained will be rather insensitive to which ISO was used to take them, so long as that ISO is above a certain point.

BP: " Image noise is constant above some ISO gain value "...

But don't we also need to say that this is only true if the "exposure" is "fixed" in PP?

No, it's only true if the exposure is held fixed (ie constant) at the time the image is recorded. And by image noise I mean noise/signal; of course, when the exposure is held fixed, the recorded light signal is held fixed.

--
emil
--



http://theory.uchicago.edu/~ejm/pix/20d/

 

[thomasnb]

No, it's only true if the exposure is held fixed (ie constant) at the time the image is recorded.

and, if Joofa is right, during the time the image is recorded. Why do I suspect one of those moments is coming on again?

--
thomas

 

[thomasnb]

is this is the best result you can show.

I'd do it more like this.





still not great, the problem with that image was the small exposure and mixing three different colour temperature light sources. Tricky.
--
thomas

 

[chuxter]

BP: " Image noise is constant above some ISO gain value "...

But don't we also need to say that this is only true if the "exposure" is "fixed" in PP?

No, it's only true if the exposure is held fixed (ie constant) at the time the image is recorded. And by image noise I mean noise/signal; of course, when the exposure is held fixed, the recorded light signal is held fixed.

It seems there are two uses of "fixed" in use here. One is to "hold constant"...that I'm sure is the way you were using it. The other is to "repair" or to "adjust"...that is the way I was using it. Allow me to substitute these better terms in our above discussion and edit stuff a bit...

BP: " Image noise is constant above some ISO gain value "...

But don't we also need to say that this is only true if the "exposure" is "adjusted" in PP, not "adjusted" by changing ISO gain?

No, it's only true if the exposure is held constant at the time the image is recorded. And by image noise I mean noise/signal; of course; when the exposure is held constant, the recorded light signal is held constant.

Is your comment still correct and relevant with these changes?
--
Charlie Davis
Nikon 5700, Sony R1, Nikon D50, Nikon D300
HomePage: http://www.1derful.info
“...photography for and of itself – photographs taken
from the world as it is – are misunderstood as a
collection of random observations and lucky moments...
Paul Graham

 

[ejmartin]

BP: " Image noise is constant above some ISO gain value "...

But don't we also need to say that this is only true if the "exposure" is "fixed" in PP?

No, it's only true if the exposure is held fixed (ie constant) at the time the image is recorded. And by image noise I mean noise/signal; of course, when the exposure is held fixed, the recorded light signal is held fixed.

It seems there are two uses of "fixed" in use here. One is to "hold constant"...that I'm sure is the way you were using it. The other is to "repair" or to "adjust"...that is the way I was using it. Allow me to substitute these better terms in our above discussion and edit stuff a bit...

BP: " Image noise is constant above some ISO gain value "...

But don't we also need to say that this is only true if the "exposure" is "adjusted" in PP, not "adjusted" by changing ISO gain?

No, it's only true if the exposure is held constant at the time the image is recorded. And by image noise I mean noise/signal; of course; when the exposure is held constant, the recorded light signal is held constant.

Is your comment still correct and relevant with these changes?
--

Since by image noise I stated that I meant noise/signal, my statement is true regardless of what you do in post wrt software signal amplification. Noise and signal are amplified in the same proportion, and noise/signal stays fixed. In the ISO regime under discussion, the same is true of analog amplification by dialing the ISO in camera.

--
emil
--



http://theory.uchicago.edu/~ejm/pix/20d/

 

[DSPographer]

[snip]

The camera calls the base sensitivity setting 200 ISO, but the data from DxO (and others) indicates that when set to 200 ISO, the D300's sensitivity is actually more like 150 ISO.

There is a good reason that the DXOmark ISO is not the same as the manufacturer's ISO for most D-SLR cameras. The manufacturer's ISO is the recommended exposure index (REI) which is what is used to set the camera exposure and the brightness of the raw conversion. The DXOmark value is the saturation ISO which is the ISO value determined by where the sensor saturates then calculating middle gray using an 18% gray point down from that. In a camera with more raw dynamic range than will fit in a standard jpeg without tone mapping or looking extremely flat, the manufacturer has a choice of where to recommend the exposure be set: in other words where the extra dynamic range in the raw data should be allocated. It is normal to assign some of the extra raw dynamic range to highlight preservation which results in the saturation ISO being lower than the REI ISO. In cameras with small sensors there is not much extra raw dynamic range than what will fit in the jpeg so for them the REI ISO and saturation ISO tend to be about the same.

 

[Nick in Shanghai]

The reason that people have difficulty with it is possibly because, like you, big (or large) exposure is a term they can't grasp.

The reason is because they are not photographic terms and never have been.
What you are doing is over exposing. Or at least that's what it sounds like.

The technique doesn't apply really to film, because it doesn't have a linear characteristic to light.

I's not the technique, it's the term. I've never heard a professional utter 'big exposure in my life' and I hope I never will. It's meaningless and completely unspecific.

If you want to be taken seriously or more seriously a grasp of the correct terms might help.

I'm not an electrical engineer but I'm sure 'big volts' is not a recognized term in that field either.

--
Nick in Shanghai.

 

[chuxter]

BP: " Image noise is constant above some ISO gain value "...

But don't we also need to say that this is only true if the "exposure" is "fixed" in PP?

No, it's only true if the exposure is held fixed (ie constant) at the time the image is recorded. And by image noise I mean noise/signal; of course, when the exposure is held fixed, the recorded light signal is held fixed.

It seems there are two uses of "fixed" in use here. One is to "hold constant"...that I'm sure is the way you were using it. The other is to "repair" or to "adjust"...that is the way I was using it. Allow me to substitute these better terms in our above discussion and edit stuff a bit...

BP: " Image noise is constant above some ISO gain value "...

But don't we also need to say that this is only true if the "exposure" is "adjusted" in PP, not "adjusted" by changing ISO gain?

No, it's only true if the exposure is held constant at the time the image is recorded. And by image noise I mean noise/signal; of course; when the exposure is held constant, the recorded light signal is held constant.

Is your comment still correct and relevant with these changes?
--

Since by image noise I stated that I meant noise/signal, my statement is true regardless of what you do in post wrt software signal amplification. Noise and signal are amplified in the same proportion, and noise/signal stays fixed. In the ISO regime under discussion, the same is true of analog amplification by dialing the ISO in camera.

Can I put that down as a "Yes"? ;-)

--
Charlie Davis
Nikon 5700, Sony R1, Nikon D50, Nikon D300
HomePage: http://www.1derful.info
“...photography for and of itself – photographs taken
from the world as it is – are misunderstood as a
collection of random observations and lucky moments...
Paul Graham

 

[Iron_Mike]

• Usually, when people talk about "noise", they mean the apparent noise , which is the NSR (noise-to-signal ratio): http://www.josephjamesphotography.com/equivalence/#noise

• That said, most people don't really know what "noise" is. They think it's just something the sensor unwittingly "adds" to the image.

• When people finally do understand what noise is (standard deviation from the mean signal for a given frequency -- see the above link), then progess can be made.

• The primary source of apparent noise in an image is the light itself. High ISO images are more noisy not because the ISO is higher, but because the shutter speed is higher, which means less light falls on the sensor.

• The sensor and supporting software do contribute to the apparent noise. However, their contribution is usually less at higher ISOs than at lower ISOs. But since the apparent noise at higher ISOs is intrinsically higher since less light is reaching the sensor, people incorrectly believe that the sensor "adds" more noise to the image at higher ISO settings, and fail to make the connection that it is instead the lesser amount of light getting to the sensor that causes the increase in apparent noise.

• Thus, if you could take an image of a scene at a given f-ratio and shutter speed, the higher ISO setting would usually result in less apparent noise, but the higher the ISO, the more of the image would be in danger of oversaturation (blown highlights).

• Hence, the "correct exposure" simply means achieving the best balance of maximizing the total amount of light that falls on the sensor vs how much of the image is oversaturated (blown) vs the necessary shutter speed to minimize motion blur and/or camera shake vs the aperture required for the desired DOF / image sharpness. In other words, purely subjective.

Is that "crackpotish" enough?

Oh dear, more incorrect "science". As usual, some truth thrown in to make the assertion seem reasonable. When it comes to sensor noise we are talking quantum physics, not the easiest topic to explain on a forum...

 

[thomasnb]

The reason that people have difficulty with it is possibly because, like you, big (or large) exposure is a term they can't grasp.

The reason is because they are not photographic terms and never have been.

Which is not a photographic term? 'Exposure' or 'big'? Would you have objected if I'd said 'big aperture'?

What you are doing is over exposing. Or at least that's what it sounds like.

Perhaps you could explain to me what you mean by 'over exposing'.

The technique doesn't apply really to film, because it doesn't have a linear characteristic to light.

I's not the technique, it's the term. I've never heard a professional utter 'big exposure in my life' and I hope I never will. It's meaningless and completely unspecific.

I explained the meaning, and it is entirely specific. Since the unit of exposure is lux seconds, it means use as big an exposure (in lux seconds) as you can. If you don't like the term, I asked you for a more acceptable alternative. Presumably we have to stick with 'exposure' since it does have a well defined meaning, so as an alternative we could have:
large exposure (I've used that too)
high exposure (more misleading than 'big or large')
I think I'm about out there, waiting for your idea.

If you want to be taken seriously or more seriously a grasp of the correct terms might help.

I've asked you what the correct term might be. Care to be a little more expansive with your expertise.

I'm not an electrical engineer but I'm sure 'big volts' is not a recognized term in that field either.

Well, it's a colloquialism, like big exposure. Not quite comparable, 'big lux seconds' would be closer to it. However, I'm not sure the unit 'lux seconds' has entered the vernacular in the same way as the Volt. However, if you said to any electrical engineer 'don't touch that wire, it's got big volts on it', I think they might take the message.

--
thomas

 

[thomasnb]

• Usually, when people talk about "noise", they mean the apparent noise , which is the NSR (noise-to-signal ratio): http://www.josephjamesphotography.com/equivalence/#noise

• That said, most people don't really know what "noise" is. They think it's just something the sensor unwittingly "adds" to the image.

• When people finally do understand what noise is (standard deviation from the mean signal for a given frequency -- see the above link), then progess can be made.

• The primary source of apparent noise in an image is the light itself. High ISO images are more noisy not because the ISO is higher, but because the shutter speed is higher, which means less light falls on the sensor.

• The sensor and supporting software do contribute to the apparent noise. However, their contribution is usually less at higher ISOs than at lower ISOs. But since the apparent noise at higher ISOs is intrinsically higher since less light is reaching the sensor, people incorrectly believe that the sensor "adds" more noise to the image at higher ISO settings, and fail to make the connection that it is instead the lesser amount of light getting to the sensor that causes the increase in apparent noise.

• Thus, if you could take an image of a scene at a given f-ratio and shutter speed, the higher ISO setting would usually result in less apparent noise, but the higher the ISO, the more of the image would be in danger of oversaturation (blown highlights).

• Hence, the "correct exposure" simply means achieving the best balance of maximizing the total amount of light that falls on the sensor vs how much of the image is oversaturated (blown) vs the necessary shutter speed to minimize motion blur and/or camera shake vs the aperture required for the desired DOF / image sharpness. In other words, purely subjective.

Is that "crackpotish" enough?

Oh dear, more incorrect "science".

Which bit, in particular, are you taking issue with.

As usual, some truth thrown in to make the assertion seem reasonable. When it comes to sensor noise we are talking quantum physics, not the easiest topic to explain on a forum...

Well, we have at least one participant in this discussion who understands quantum physics rather well, and he hasn't objected yet.
--
thomas

 

[arachnophilia]

and that's what the demonstration in the OP shows -- although it's not clear from the picture alone that exposure is different.

Your last line is the crux of the problem...there were not proper explanations of what the pictures really showed.

perhaps not. i dunno. i figured it out pretty quick from your analysis. i'd have to go look at the original posts, but that's neither here nor there.

I agree completely that Thomas is trying ... ;-)

perhaps not in the sense that you mean "trying."

Lately, he seems to have gotten the message that he needs to use fewer, better constructed sentences if he wants to be a part of the solution.

it's not really his fault. i've been in several discussion, on other matters, on these here interwebs, where the person i was debating with wanted whole fields of scientific study that you could devote your entire academic life to studying one small aspect thereof... all condensed down to a few sentances and in small enough words that a four year old could understand it. and it just doesn't work that way. it can be extremely frustrating trying to relay a sophisticated and technical understanding in a way that actually betrays the amount of study you've had to put into it yourself. if one could do such a thing, what's the purpose of studying in the first place?

trust me, the communication issue is not just here. it's anything to do with anything scientific, or mathematical. you have to take a few years of class just to know what half the words mean.