Nature Science+Photography Volume 3: Visual Sharpness
Volume 3 of the Nature Science+Photography series is dedicated to the subject of visual sharpness:
What is visual sharpness?
Why are resolving power and edge sharpness decisive for our perception of sharpness?
On which factors does the resolving power of the visual system depend?
Which optical principles determine image sharpness?
What is depth of field, and how does it relate to the various photographic parameters?
How is the resolving power of photographic components—and of the image itself—quantified?
How can we enhance the edge sharpness of our photographs?
The first chapter begins by establishing that visual sharpness constitutes our sensation of the distinctness of object edges: the more clearly we perceive these edges, the greater our impression of sharpness. Since this clarity corresponds directly to the difference in brightness at the edge, the impression of visual sharpness is essentially a byproduct of our perception of contrast. In addition to contrast—which we also refer to as edge sharpness—resolving power plays a significant role in the perception of sharpness; this first section explains in detail the specific characteristics of the visual system in this regard.
The second chapter introduces the optical and geometric principles underlying the concept of sharpness. Based on these principles, it becomes evident that while true geometric sharpness exists only within a single plane, perceived sharpness can extend beyond that single plane. We refer to this perceived image sharpness as depth of field; the majority of this chapter examines how depth of field relates to key photographic parameters: aperture, shooting distance, focal length, focus point, and image format.
The third chapter addresses the resolving power of various photographic components—specifically optics, image sensors/media, and output devices—and explains how their combined resolving power is calculated.
The fourth chapter offers practical guidance on how to enhance the edge sharpness of photographic images, covering both analog and digital workflows.
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Content
Introduction 5
1. Visual sharpness
Positioning: What is visual sharpness 8
The resolving power of the visual system 10
Diffraction as a physical limitation 11
The arrangement of the photoreceptors on the retina 14
The neuronal circuitry of the photoreceptors 16
The quality of ophthalmic optics 17
The brightness 18
The contrast 19
The color 23
The total resolving power of the visual system 24
Contour sharpness 27
2. Image sharpness I: Optics, geometric sharpness and depth of field
The focus: True geometric sharpness only exitsts in one plane 32
Circle of confusion and depth of field: Perceived sharpness extends over more than one plane 34
Geometry and calculation of the depth of field 37
Depth of field and aperture 42
Depth of field and subject distance 45
Depth of field and focal length 48
Depth of field and focus point 53
Depth of field and image format 57
Estimating depth of field when taking a picture 61
Between aberration and diffraction: Not every aperture is a good aperture 65
Interjection: The mathematical short path to a sharp image 73
3. Image sharpness II: The photographic resolving power
The Modulation Transfer Function 78
The resolving power of optics 81
The resolving power of analog image carriers 83
The resolving power of digital image carriers
Information Theory: The fundamental limitation 85
The Kell Factor and the theoretical maximum resolution 87
The resolution behavior of colored structures 88
Smaller pixels = higher resolution? 92
The resolving power of digital output devices
Inkjet printer 92
Laser imagesetter 95
Dye-sublimation printer 95
The overall resolution of an imaging system 95
Resolving power, viewing distance and print size 97
Practical evaluation of the recording systems 102
4. Image sharpness III: Edge sharpness
Methods of edge sharpening 106
Greater edge sharpness by better shooting technique 106
Greater edge sharpness by active image composition 107
Greater edge sharpness by „sharp development“ 109
Greater edge sharpness by analog unsharp masking 111
Greater edge sharpness by digital unsharp masking 112
5. Appendix 120
Jörg Sczepek
Nature Science+Photography
Volume 3: Visual Sharpness
6.69x9.61" / 17x24.5 cm
65 color images, 125 pages, 12.99 $
ISBN 9798248956739
Independently published
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