Max theoretical resolution of scanned images.

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Discussion Overview

The discussion revolves around the maximum theoretical resolution of scanned images, specifically focusing on A4 paper and the implications of using different wavelengths of light for scanning. Participants explore concepts related to optical resolution, microscopy techniques, and the physical properties of materials being scanned.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant calculates the maximum resolution of a scanned A4 image to be approximately 1.56 terapixels based on the dimensions of the paper and the average resolution of light at 200nm.
  • Another participant notes that visible light has wavelengths ranging from 400 to 700nm and mentions microscopy techniques that can resolve features smaller than the wavelength of light.
  • It is suggested that the maximum resolution of a simple optical scanner is half the wavelength of light, leading to a theoretical maximum resolution of around 200nm.
  • Some participants question the assumption that the scanned image possesses high resolution, indicating that the actual resolution may depend on the characteristics of the material being scanned, such as a graphite drawing.
  • There is a discussion about the limitations of resolution based on the size of the graphite molecules and the physical properties of the canvas or paper pulp particles.
  • One participant emphasizes that the determination of maximum resolution for a graphite drawing may not align with traditional definitions of an image, suggesting it is more of a physical object.

Areas of Agreement / Disagreement

Participants express differing views on the maximum resolution achievable with scanned images, particularly regarding the implications of using different wavelengths of light and the nature of the materials being scanned. There is no consensus on the exact maximum resolution or the factors influencing it.

Contextual Notes

Participants acknowledge that the resolution may be limited by various factors, including the physical properties of the scanned materials and the assumptions made about the image quality. The discussion reflects uncertainty regarding the definitions and measurements of resolution in different contexts.

Energize
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May seem like a bizarre question but I was wondering what the maximum possible resolution of a scanned A4 image would be.

A4 paper is 0.297m x 0.21m, average resolution of light is 200nm.

So I get,

(0.297m / 200x10^-9m) x (0.21m / 200x10^-9m) = 1.56 terapixels

Is this about right? Would we be able to use violet light for a greyscale image to achieve a higher resolution, and would we have to stick to the resolution of red light to get an accurate scan with a colour image?
 
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Energize said:
average resolution of light is 200nm.
Visible light has a wavelength of around 400 to 700nm
There are microscopy techniques that will give you position of an edge that is smaller than wavelength and you can detect the position of small high contrast objects that are smaller than a wavelength

And of course some non-light microscopes can resolve individual atoms
 
This all assumes that the image being scanned is that high of a resolution.
 
mgb_phys said:
Visible light has a wavelength of around 400 to 700nm
There are microscopy techniques that will give you position of an edge that is smaller than wavelength and you can detect the position of small high contrast objects that are smaller than a wavelength

And of course some non-light microscopes can resolve individual atoms

The max resolution of a simple optical scanner is half the wavelength though is it not? Giving a max resolution of 200nm and average of 275nm?

russ_watters said:
This all assumes that the image being scanned is that high of a resolution.

How does one determine the max resolution of say a graphite drawing, I assume it is related the size of the graphite molecules?
 
Energize said:
How does one determine the max resolution of say a graphite drawing, I assume it is related the size of the graphite molecules?
I'm not sure you can really say a graphite drawing is an "image" - it is more of a physical object.

The useful resolution is probably limited to the size of the fabric of the canvas or paper pulp particles.
 
Energize said:
The max resolution of a simple optical scanner is half the wavelength though is it not? Giving a max resolution of 200nm and average of 275nm?
The diffraction limit of a NA \approx 1 objective is about 0.5wavelengths
But this is a very simplistic picture of resolution
 

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