Return of Interesting article on DxO about 5D III and D800...

Started Apr 10, 2013 | Discussions
John Sheehy
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Return of Interesting article on DxO about 5D III and D800...
Apr 10, 2013

When the original thread hit 150, what was being debated seemed to be what about what resolution is a measure of.  I don't think that there is a single meaning of resolution at all.  There are different kinds of resolution, one relevant more for one need than another.

Many people tend to shoot at medium and wide FOVs, and to those people, the resolution potential of the entire sensor and/or the system resolution with a lens is important.  Other people are almost always working with lenses that have too little magnification for their needs.  For example, only dead birds let you fill the frame the way you want all the time, and a photographer in the stands can't get the kinds of shots that they could get standing in the field, interfering with the game.  Jupiter only gets infinitesimally larger on the sensor if you drive towards it.  For such needs, higher pixel density is worth more, most of the time, than full sensor performance.

Both types of resolution should be measured.  For a regular array of photosites, however, in columns and rows, a single metric, either in the form of DxOMark's "Perceptual Megapixels", or a resolution at a single contrast level, tell a very fractional story, and can often imply quality when, in fact, the result is actually aliasing.  The problem is that we have inherited methods of measuring resolution from film, which has an irregular placement of grains, and has the ability to properly center a point, or edge, on average.  A simple array of rows and columns of pixels can not do that, unless the transient takes about three pixels inclusive to occur, due to either an anti-aliasing filter, or a lack of high resolution content due to the lens.

Because pixel count or density puts a brick-wall limit on resolution at any contrast level, and AA filters drop the contrast approaching that resolution abruptly, one can not tell if the single contrast criterion used to measure monolithic resolution occurs in the natural contrast falloff part of the curve, or in the zone affected by the AA filter, or near the brick wall posed by the discrete pixels.  So, a monolithic measurement leaves the rest of the contrast vs frequency curve undefined.  The real curve is actually not a single curve, as it should split at the frequency where aliasing starts to take effect, with a higher trend for maximum contrast due to ideal pixel-to-subject alignment, and the lower trend for unlucky alignment (a transient right in the middle of a pixel).

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Mako2011
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not sharpness
In reply to John Sheehy, Apr 10, 2013

You seem to be mixing terms and describing sharpness but calling it resolution.  Resolution only describes how much detail a camera/lens is capable of capturing — and not necessarily the quality of the detail that is captured. The problem, in these types of discussions, is that folks keep mixing related terms an using them to describe inaccurately a concept

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qianp2k
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Re: not sharpness
In reply to Mako2011, Apr 10, 2013

Mako2011 wrote:

You seem to be mixing terms and describing sharpness but calling it resolution.  Resolution only describes how much detail a camera/lens is capable of capturing — and not necessarily the quality of the detail that is captured. The problem, in these types of discussions, is that folks keep mixing related terms an using them to describe inaccurately a concept

Your understanding of resolution that purely based on the amount of pixels is very wrong. I know on your logic 41mp Nokia 808 has double "resolution" than 21mp 5D2. The only problem is that when you see such 41mp photos from Nokia 808, you hardly can figure out much detail, or maybe your eyes are different from all others?

DXOMark correctly test the real resolution (P-MPix) that in my words “Fine Detail” that human eyes can resolve that only matters.  Otherwise your paper resolution is just an Utopia that you can feel but you really cannot see

It's not regular sharpness or acutance on your understanding because latter supposedly can be enhanced in software processing. However the fine details only can obtained thru sensor-lens system captured.

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In reply to qianp2k, Apr 10, 2013

qianp2k wrote:

Mako2011 wrote:

You seem to be mixing terms and describing sharpness but calling it resolution.  Resolution only describes how much detail a camera/lens is capable of capturing — and not necessarily the quality of the detail that is captured. The problem, in these types of discussions, is that folks keep mixing related terms an using them to describe inaccurately a concept

Your understanding of resolution that purely based on the amount of pixels is very wrong. I know on your logic 41mp Nokia 808 has double "resolution" than 21mp 5D2. The only problem is that when you see such 41mp photos from Nokia 808, you hardly can figure out much detail, or maybe your eyes are different from all others?

DXOMark correctly test the real resolution (P-MPix) that in my words “Fine Detail” that human eyes can resolve that only matters.  Otherwise your paper resolution is just an Utopia that you can feel but you really cannot see

It's not regular sharpness or acutance on your understanding because latter supposedly can be enhanced in software processing. However the fine details only can obtained thru sensor-lens system captured.

Once again you have interjected unrelated terms. Not being able to understand the difference between the term "resolution" and other concepts/terms is the source of your misconceptions. A common theme. You simply can not define or conceptualize the term "resolution" . A barrier too communication you may never be able to overcome.

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Re: unable
In reply to Mako2011, Apr 10, 2013

Mako2011 wrote:

qianp2k wrote:

Mako2011 wrote:

You seem to be mixing terms and describing sharpness but calling it resolution.  Resolution only describes how much detail a camera/lens is capable of capturing — and not necessarily the quality of the detail that is captured. The problem, in these types of discussions, is that folks keep mixing related terms an using them to describe inaccurately a concept

Your understanding of resolution that purely based on the amount of pixels is very wrong. I know on your logic 41mp Nokia 808 has double "resolution" than 21mp 5D2. The only problem is that when you see such 41mp photos from Nokia 808, you hardly can figure out much detail, or maybe your eyes are different from all others?

DXOMark correctly test the real resolution (P-MPix) that in my words “Fine Detail” that human eyes can resolve that only matters.  Otherwise your paper resolution is just an Utopia that you can feel but you really cannot see

It's not regular sharpness or acutance on your understanding because latter supposedly can be enhanced in software processing. However the fine details only can obtained thru sensor-lens system captured.

Once again you have interjected unrelated terms. Not being able to understand the difference between the term "resolution" and other concepts/terms is the source of your misconceptions. A common theme. You simply can not define or conceptualize the term "resolution" . A barrier too communication you may never be able to overcome.

Terms are not really that important in this discussion. I just want to point out that your interpretation and understanding of DXOMark P-MPix test is very wrong. DXOMark uses terms sharpness and resolution interchangeably but they are not regular sharpness/acutance that you could enhance in LR for example. It's the resolution that human eyes can actually resolve that makes very sense.

I know I keep using Nokia 808 as an example and you don't want to address but that's exact the case to show your understanding is wrong. There is simply no such sensor resolution but only a system (sensor+lens) resolution  that is actual fine detail that system can resolve and present to human eyes can actually see.

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cpkuntz
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Re: Return of Interesting article on DxO about 5D III and D800...
In reply to John Sheehy, Apr 10, 2013

This isn't a half-bad introduction to the concept.

From Wikipedia:

http://en.wikipedia.org/wiki/Optical_resolution

Some optical sensors are designed to detect spatial differences in electromagnetic energy. These include photographic film, solid-state devices (CCD, CMOS detectors, and infrared detectors like PtSi and InSb), tube detectors (vidicon, plumbicon, and photomultiplier tubes used in night-vision devices), scanning detectors (mainly used for IR), pyroelectric detectors, and microbolometer detectors. The ability of such a detector to resolve those differences depends mostly on the size of the detecting elements.

Spatial resolution is typically expressed in line pairs per millimeter (lppmm), lines (of resolution, mostly for analog video), contrast vs. cycles/mm, or MTF (the modulus of OTF)). The MTF may be found by taking the two-dimensional Fourier transform of the spatial sampling function. Smaller pixels result in wider MTF curves and thus better detection of higher frequency energy.

This is analogous to taking the Fourier transform of a signal sampling function; as in that case, the dominant factor is the sampling period, which is analogous to the size of the picture element (pixel).

Other factors include pixel noise, pixel cross-talk, substrate penetration, and fill factor.

A common problem among non-technicians is the use of the number of pixels on the detector to describe the resolution. If all sensors were the same size, this would be acceptable. Since they are not, the use of the number of pixels can be misleading. For example, a 2 megapixel camera of 20 micrometre square pixels will have worse resolution than a 1 megapixel camera with 8 micrometre pixels, all else being equal.

For resolution measurement, film manufacturers typically publish a plot of Response (%) vs. Spatial Frequency (cycles per millimeter). The plot is derived experimentally. Solid state sensor and camera manufacturers normally publish specifications from which the user may derive a theoretical MTF according to the procedure outlined below. A few may also publish MTF curves, while others (especially intensifier manufacturers) will publish the response (%) at the Nyquist frequency, or, alternatively, publish the frequency at which the response is 50%.

To find a theoretical MTF curve for a sensor, it is necessary to know three characteristics of the sensor: the active sensing area, the area comprising the sensing area and the interconnection and support structures ("real estate"), and the total number of those areas (the pixel count). The total pixel count is almost always given. Sometimes the overall sensor dimensions are given, from which the real estate area can be calculated. Whether the real estate area is given or derived, if the active pixel area is not given, it may be derived from the real estate area and thefill factor, where fill factor is the ratio of the active area to the dedicated real estate area."

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cpkuntz
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Re: Return of Interesting article on DxO about 5D III and D800...
In reply to cpkuntz, Apr 10, 2013
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Erik Magnuson
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Perceptual....
In reply to John Sheehy, Apr 10, 2013

John Sheehy wrote:

For a regular array of photosites, however, in columns and rows, a single metric, either in the form of DxOMark's "Perceptual Megapixels", or a resolution at a single contrast level, tell a very fractional story, and can often imply quality when, in fact, the result is actually aliasing.

It should be obvious that any single figure of merit can tell only a fractional story.  The more important question is does a story involving "Perceptual Megapixels"  correlate well with the perception of detail in real world usage?  In this case, aliasing or not is mostly irrelevant because it contributes to the "perception" of detail.   Certainly when comparing lenses with the same sensor, aliasing is important as it can only occur when the lens images enough detail to alias.

The problem is that we have inherited methods of measuring resolution from film,

Lens resolution has been measured without using film.

So, a monolithic measurement leaves the rest of the contrast vs frequency curve undefined.  The real curve is actually not a single curve, as it should split at the frequency where aliasing starts to take effect, with a higher trend for maximum contrast due to ideal pixel-to-subject alignment, and the lower trend for unlucky alignment (a transient right in the middle of a pixel).

Other than for bragging rights, how much does this matter?  In the real world there is also copy variation, field curvature, and even rounding error (P-Mpix is only reported to at most two digits: is 16 vs. 17 really 16.4 vs. 16.5?)

Of your points, the fact that P-Mpix is computed over the entire frame while most subjects are not is probably the most perception relevant.

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Mako2011
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exactly
In reply to qianp2k, Apr 10, 2013

qianp2k wrote:

Terms are not really that important in this discussion.

That commentary is exactly why you so often go off topic. You don't understand the importance of a common reference point and reply in another off topic manner to a post by me while not being able relate to the discussion raised by the OP. Predictable. Good luck

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Re: exactly
In reply to Mako2011, Apr 10, 2013

Just a curiosity that why you keep changing subject line (in your posts' titles) if you really want to stay in topic?

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John Sheehy
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Re: not sharpness
In reply to Mako2011, Apr 11, 2013

Mako2011 wrote:

You seem to be mixing terms and describing sharpness but calling it resolution.  Resolution only describes how much detail a camera/lens is capable of capturing — and not necessarily the quality of the detail that is captured. The problem, in these types of discussions, is that folks keep mixing related terms an using them to describe inaccurately a concept

Did you actually read my post?  It seems very unlikely, given your response.

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qianp2k
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Re: not sharpness
In reply to John Sheehy, Apr 11, 2013

John Sheehy wrote:

Mako2011 wrote:

You seem to be mixing terms and describing sharpness but calling it resolution.  Resolution only describes how much detail a camera/lens is capable of capturing — and not necessarily the quality of the detail that is captured. The problem, in these types of discussions, is that folks keep mixing related terms an using them to describe inaccurately a concept

Did you actually read my post?  It seems very unlikely, given your response.

He doesn't care the quality of pixels (or detail) that's why I keep using 41mp Nokia 808 to remind him  For him, 41mp is 41mp regardless of the huge loss thru imperfect lens and loss in crop enlargement, regardless if his eyes actually can resolve details or not.  He denies crop penalty in other posts in other threads before (but all these concepts are related to each other)  that's why I also keep using another vivid case that nobody should buy 600mm lens that all PJs should use 300mm on 2.0x crop or even better 30mm on 20x crop, LOL.  I know he will again suggest me off-topic  But if he cannot address these two vivid cases (Nokia 808 and 600mm lens), he doesn't understand resolution or perceptual sharpness (resolution or fine details as I prefer to call)

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Mako2011
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I did
In reply to John Sheehy, Apr 11, 2013

John Sheehy wrote:

Mako2011 wrote:

You seem to be mixing terms and describing sharpness but calling it resolution.  Resolution only describes how much detail a camera/lens is capable of capturing — and not necessarily the quality of the detail that is captured. The problem, in these types of discussions, is that folks keep mixing related terms an using them to describe inaccurately a concept

Did you actually read my post?  It seems very unlikely, given your response.

I read it all many times. You said "... I don't think that there is a single meaning of resolution at all".

In fact,  Resolution only describes how much detail a camera/lens is capable of capturing. Mft is how that is measured. The other things you discussed being measured relate more to sharpness. Sharpness is not resolution. 

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aftab
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Re: Return of Interesting article on DxO about 5D III and D800...
In reply to John Sheehy, Apr 11, 2013

Strictly speaking, this is not a reply to your OP only, it is more like a response to everything posted so far.

I see lots of accusations here, people don't understand the terms resolution and sharpness clearly etc. And to support this assumption there are lots of articles in the web too. Funny, really!

Scenario A

One doesn't need to be a rocket scientist to know that A is sharper than B. We often get lost in definitions and numbers and frequencies etc. But one can easily see sharpness. In this case it is about more contrast and more well defined edges (abrupt and clear transition of information from black to white or Actuance). So, if we really insist on defining sharpness we can say Sharpness = Clarity.

How about resolution?

Scenario B

Does anyone really think that some people don't know that A has more resolution than B? Yeah, it shows so many line pairs/so much area.. yaada yaada and one can talk about how Fourier transform or that nyquist frequency can explain them. But everybody knows what they see, Resolution = Detail.

Now, we must talk about real world, because that is the norm in this forum (as if we can ever capture something that doesn't belong to this world:P).

Scenario C

A has more resolution than B, because we can count 1753 hair in A vs 1248 hair in B.

Now, let us look at scenario B and scenario C again. In both cases A looks sharper than B. What does that mean? More resolution = more sharpness. That is resolution = sharpness in this two scenarios. And almost all scenarios are like this. So, we can actually use the terms resolution and sharpness interchangeably.

At this point if you have this intense desire to shout at me and say, you don't understand nothing, please look at at scenario A again. We all understand sharpness when we see it. But some of us will hang on to the definitions forever and will deny that fact that sharpness (sharper edge transition) and resolution (detail) are the same for all practical purposes (display size, viewing distance, visual acuity etc). When you have better details in an image it is because the edges of those details are clearly defined. The portrait that shows more hair and skin pores will appears sharper than the one that shows less hair and no skin pores.

Things get a bit complicated if we try to understand how pixel count of a sensor translates into image resolution and as such image sharpness. But we know that law of diminishing return works here and better lens with higher actuance capability combined with higher MP sensor will give the sharper perceptible image than lesser lens with same sensor.

Anyways, another picture

We can say A has higher resolution. Or we can say A is sharper. Same thing.

Disclaimer: I may change my mind tomorrow morning, I am drinking wine at the moment. Australian Penfolds red wines are really nice.

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Re: Return of Interesting article on DxO about 5D III and D800...
In reply to aftab, Apr 11, 2013

Very interesting to read and excellent writing

http://www.dxomark.com/index.php/Publications/DxOMark-Reviews/Looking-for-new-photo-gear-DxOMark-s-Perceptual-Megapixel-can-help-you

DXOMark indeed uses words sharpness and resolution interchangeably as you can see in its above explanation of Perceptual Megapixel. It uses the word "sharpness" but then it explains the reasons to change to P-MPix unit,

This measurement bypasses the problems inherent to MTF:

  • Describes resolution with a single number,
  • Correlates with the way the human vision perceives resolution
  • Uses a unit that is well-known to photographers — the megapixel.

Anyway DXOMark's sharpness is not regular sharpness you can enhance in software but a resolution that human eyes can perceive - perceptural sharpness expressed in MP unit.

aftab wrote:

Strictly speaking, this is not a reply to your OP only, it is more like a response to everything posted so far.

I see lots of accusations here, people don't understand the terms resolution and sharpness clearly etc. And to support this assumption there are lots of articles in the web too. Funny, really!

Scenario A

One doesn't need to be a rocket scientist to know that A is sharper than B. We often get lost in definitions and numbers and frequencies etc. But one can easily see sharpness. In this case it is about more contrast and more well defined edges (abrupt and clear transition of information from black to white or Actuance). So, if we really insist on defining sharpness we can say Sharpness = Clarity.

How about resolution?

Scenario B

Does anyone really think that some people don't know that A has more resolution than B? Yeah, it shows so many line pairs/so much area.. yaada yaada and one can talk about how Fourier transform or that nyquist frequency can explain them. But everybody knows what they see, Resolution = Detail.

Now, we must talk about real world, because that is the norm in this forum (as if we can ever capture something that doesn't belong to this world:P).

Scenario C

A has more resolution than B, because we can count 1753 hair in A vs 1248 hair in B.

Now, let us look at scenario B and scenario C again. In both cases A looks sharper than B. What does that mean? More resolution = more sharpness. That is resolution = sharpness in this two scenarios. And almost all scenarios are like this. So, we can actually use the terms resolution and sharpness interchangeably.

At this point if you have this intense desire to shout at me and say, you don't understand nothing, please look at at scenario A again. We all understand sharpness when we see it. But some of us will hang on to the definitions forever and will deny that fact that sharpness (sharper edge transition) and resolution (detail) are the same for all practical purposes (display size, viewing distance, visual acuity etc). When you have better details in an image it is because the edges of those details are clearly defined. The portrait that shows more hair and skin pores will appears sharper than the one that shows less hair and no skin pores.

Things get a bit complicated if we try to understand how pixel count of a sensor translates into image resolution and as such image sharpness. But we know that law of diminishing return works here and better lens with higher actuance capability combined with higher MP sensor will give the sharper perceptible image than lesser lens with same sensor.

Anyways, another picture

We can say A has higher resolution. Or we can say A is sharper. Same thing.

Disclaimer: I may change my mind tomorrow morning, I am drinking wine at the moment. Australian Penfolds red wines are really nice.

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Re: Return of Interesting article on DxO about 5D III and D800...
In reply to aftab, Apr 11, 2013

aftab wrote:

......... We can say A has higher resolution. Or we can say A is sharper. Same thing.

If you wish to change the definition of resolution to merely mean how sharp something appears, then I'd agree with everything you've said here.

Otherwise - no - not the same thing.

Disclaimer: I may change my mind tomorrow morning, I am drinking wine at the moment. Australian Penfolds red wines are really nice.

My experience is that a good red will make things appear much simpler than they might actually be.

PS - I'm having a red too at the moment.

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Re: Return of Interesting article on DxO about 5D III and D800...
In reply to schmegg, Apr 11, 2013

schmegg wrote:

aftab wrote:

......... We can say A has higher resolution. Or we can say A is sharper. Same thing.

If you wish to change the definition of resolution to merely mean how sharp something appears, then I'd agree with everything you've said here.

Otherwise - no - not the same thing.

Disclaimer: I may change my mind tomorrow morning, I am drinking wine at the moment. Australian Penfolds red wines are really nice.

My experience is that a good red will make things appear much simpler than they might actually be.

PS - I'm having a red too at the moment.

I am not under influence of red at the moment but my eyes still see all A samples in aftab's post not only sharper but resolve more fine details

Yes sharpness and resolution are not the same but related just as noise and detail are related that you cannot separate them.  Nevertheless DXOMark's term sharpness is not the same one you might think about that can be processed in software.

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Re: Return of Interesting article on DxO about 5D III and D800...
In reply to qianp2k, Apr 11, 2013

qianp2k wrote:

schmegg wrote:

aftab wrote:

......... We can say A has higher resolution. Or we can say A is sharper. Same thing.

If you wish to change the definition of resolution to merely mean how sharp something appears, then I'd agree with everything you've said here.

Otherwise - no - not the same thing.

Disclaimer: I may change my mind tomorrow morning, I am drinking wine at the moment. Australian Penfolds red wines are really nice.

My experience is that a good red will make things appear much simpler than they might actually be.

PS - I'm having a red too at the moment.

I am not under influence of red at the moment but my eyes still see all A samples in aftab's post not only sharper but resolve more fine details

With respect - your eyes are well known around here for seeing things that don't actually exist. So I'm not surprised.

Given that each photographic comparison contains two versions of exactly the same image, the amount of detail resolved would be the same. In both photographic examples, sample A is simply sample B that has been sharpened in post. Hehe.

What you are seeing is simply sharper images, not images that have more detail.

And these examples actually demonstrate that very well.

Yes sharpness and resolution are not the same but related just as noise and detail are related that you cannot separate them.

Correct - they are not the same.

Nevertheless DXOMark's term sharpness is not the same one you might think about that can be processed in software.

Go ahead and tell me how it's different.

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aftab
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Re: Return of Interesting article on DxO about 5D III and D800...
In reply to schmegg, Apr 11, 2013

schmegg wrote:

aftab wrote:

......... We can say A has higher resolution. Or we can say A is sharper. Same thing.

If you wish to change the definition of resolution to merely mean how sharp something appears, then I'd agree with everything you've said here.

Otherwise - no - not the same thing.

Disclaimer: I may change my mind tomorrow morning, I am drinking wine at the moment. Australian Penfolds red wines are really nice.

My experience is that a good red will make things appear much simpler than they might actually be.

PS - I'm having a red too at the moment.

Red is gold.

Einstein said, we should make things simple, but not simpler. Maybe I did make it simpler. Yeah, when I said, it is the same thing, it is not true for scenario A. Definitions or concepts that these two entities are different work for scenario A. But scenario A is totally theoretical. It helps us to understand the concept, but that's not how we take pictures or process them. Our pictures are more like scenario B or C and that's where two concepts overlap and become indistinguishable.

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John Sheehy
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Re: not sharpness
In reply to qianp2k, Apr 11, 2013

qianp2k wrote:

John Sheehy wrote:

Mako2011 wrote:

You seem to be mixing terms and describing sharpness but calling it resolution.  Resolution only describes how much detail a camera/lens is capable of capturing — and not necessarily the quality of the detail that is captured. The problem, in these types of discussions, is that folks keep mixing related terms an using them to describe inaccurately a concept

Did you actually read my post?  It seems very unlikely, given your response.

He doesn't care the quality of pixels (or detail) that's why I keep using 41mp Nokia 808 to remind him  For him, 41mp is 41mp regardless of the huge loss thru imperfect lens and loss in crop enlargement, regardless if his eyes actually can resolve details or not.

40MP pixels is and always is, 40MP.  "MPs" is the maximum number of sampling elements, regardless of potential contrast.  Sampling should, ideally, be soft, at the pixel level.  Not by having too strong an AA filter, or by having a soft lens, but by having enough pixels that pixel softness is the result.  You can not record an image without spatial distortion, if you have high contrast in the RAW capture at the pixel level.  It is impossible.  A 40MP sensor will always be able to record alternating darker and lighter lines on alternating lines of pixels, at some level of contrast, unless the AA filter or diffraction is ridiculous, in which case the noise will be much stronger than the signal.

In the case of the Nokia, it doesn't seem that the system is getting much, if any, undersampling, which means that the 40MP is a good thing.  It will downsample to a much better 12MP image than a 12MP sensor, and it will be much better printed large at 40MP than it would be from a 12MP sensor.  The only downside to having 40MP is speed and storage.

He denies crop penalty in other posts in other threads before (but all these concepts are related to each other)  that's why I also keep using another vivid case that nobody should buy 600mm lens that all PJs should use 300mm on 2.0x crop or even better 30mm on 20x crop, LOL.  I know he will again suggest me off-topic  But if he cannot address these two vivid cases (Nokia 808 and 600mm lens), he doesn't understand resolution or perceptual sharpness (resolution or fine details as I prefer to call)

We haven't seen the Nokia's sensor with a lens that isn't designed to sit very close to the sensor, which is probably a major reason why the 40MP images aren't as sharp at the pixel level as many other cameras.  Regardless, the 40MP still gets 40 million samples; none of them redundant.

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