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

Started Apr 10, 2013 | Discussions thread
schmegg MOD
Senior MemberPosts: 4,978
Re: Same
In reply to aftab, Apr 12, 2013

aftab wrote:

Mako2011 wrote:

aftab wrote:

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. A and B above you can count and discern the same number of lines. The resolution of A and B is the same.

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.

Not the case at all. In scenario B...the resolution of the two images is equal. Sharpness though differs.

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My opinions are my own and not those of DPR or its administration. They carry no 'special' value (except to me and Lacie of course)

I don't know if my line of thinking is right, but I invite you (and others) to it and give your opinion.

There is definition of sharpness and resolution and there is perception of them when we view a picture.

When we perceive a picture being sharp two conditions are fulfilled.

A. The picture has the details that we expect to see, either because of our past experience with the subject or because we are comparing more than one picture of the same subject side by side.

B. The details are seen clearly.

By definition these two conditions are separate entities. One is quantity. One is quality. One is resolution. One is sharpness.

Let's take a hypothetical but real world scenario. Two pictures of a piece of fabric. One taken with a FF 24 MP camera. The other with a FF 12 MP camera. Everything else including the lens used is same. 24 MP camera captured all the threads of the fabric distinctly. 12 MP camera captured 70% of the threads distinctly, rest 30% is not distinct or blurred. Now if we view these two pictures from same distance in same display size, the picture that shows 100% of the fabric threads distinctly will appears sharper than the one that shows 70% of the threads. You can extend this scenario to almost any other real life scenario, a face, a cat, a flower... almost anything that has any detail of significance. So, a picture with higher detail that matches our expectations/knowledge or better detail than another picture of the same subject in comparison will appear sharper. Simply put, we perceive higher resolution pictures as sharper than lower resolution pictures of the same subject when viewed in the same size to show the difference in detail and from the same distance. This is 'A' and this probably accounts for more than 90% of our perception of sharpness when we view see an image.

The contribution of 'B' to our perception of sharpness is minuscule compared to 'A'. After all, an information can't be seen clearly (or sharpened) if it can't be seen at all in the first place.

The condition 'A' can be emulated in many other ways we shoot. Using best aperture vs other apertures, using better lens vs poor lens etc.

I think in real life scenarios, 'detail' is the most important contributor to our perception of sharpness irrespective of how we achieve it. Yeah, we can manipulate an image and make clearer distinction between two adjacent threads, but detail remains at the heart of out perception of sharpness, the quality of detail contributing just a little.

So, from the perspective of our perception, resolution = sharpness.

So far we have looked at resolution from the perspective of sharpness. We can also do the opposite. Look at sharpness from the perspective of resolution. Any detail will be perceived as detail by a viewer if they are clear (or sharp) enough. So, if we look at the scenario A of my original post, by definition we will say A and B has the same resolution. But for a viewer B shows no detail at all (and hence no resolution), it is just a combination blurry stuffs. So, for a line pair to be a line pair (or detail to be a detail) some critical sharpness is essential. Sharpness contributes to our perception of of detail which in turn contributes to our perception of sharpness. They are inseparable.

Does my thinking make any sense, or it is all Penfold's fault?

I appreciate your posts - and I don't really disagree with most of what you say from a pragmatic standpoint.

However - I'm really not sure that it is helpful, conceptually, to attempt to espouse that resolution and sharpness are the same thing.

They are not.

Sharpness is the combination of resolution and acutance. Sharpness can vary independently of resolution. An image can be quite sharp but have low resolution (and high acutance). An image can also be soft but have high resolution (and low acutance). The best looking images have high resolution and high acutance - they appear sharp and detailed.

My personal opinion on this (as you've probably gathered as I've been pretty vocal on it - sorry) is that mixing these terms only leads to confusion down the track. You see comments like "a 5Dc out-resolves an 18MP crop" etc. These comments are made by people who are confused about these different imaging parameters - and probably because they simply have not conceptually separated and identified each for what it is (and what it is not).

I really think it's moreĀ usefulĀ to think of sharpness as what it is. And likewise resolution and acutance.

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