## Diff of /src/hugin1/hugin/xrc/data/help_en_EN/Diffraction.html[9e26cc] .. [832b36] Maximize Restore

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<a name="What_it_is" id="What_it_is"></a><h2> <span class="mw-headline">What it is</span></h2>
-<p>Diffraction in general is the bending of waves around an obstacle. In photography the light waves are bent around the edges of the aperture, causing f.e. the well known star like pattern around the sun if shot stopped down. Since diffraction affects any point of the image (not only very bright sources) it reduces general sharpness and limits effective resolution. Diffraction blurs any point to a pattern called "w:Airy disk".
+<p>Diffraction in general is the bending of waves around an obstacle. In photography the light waves are bent around the edges of the aperture, causing f.e. the well known star like pattern around the sun if shot stopped down. Since diffraction affects any point of the image (not only very bright sources) it reduces general sharpness and limits effective resolution. Diffraction blurs any point to a pattern called "w:Airy disk<a class="external" href="http://www.wikipedia.org/wiki/Airy_disk">[*]</a>".
</p>
<p>Diffraction is one of four lens based factors limiting the image sharpness. Second is aberration (f.e. <a href="Chromatic_aberration.html" title="Chromatic aberration">chromatic aberration</a>) which is determined by lens build quality. Third is de-focus or <a href="Depth_of_Field.html" title="Depth of Field">Depth of Field</a>. Fourth is motion blur due to lens shake.
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</p><p>You can balance <a href="Depth_of_Field.html" title="Depth of Field">Depth of Field</a> against diffraction. An approach is the sharpest aperture. <a href="Diffraction.html#External_links" title="Diffraction">See link at the bottom</a>.
</p>
-<p>The maximum obtainable resolution is limited by diffraction according to the Rayleigh criterion. We can safely assume the equivalent of one pixel distance as the minimum resolvable distance required by the Rayleigh criterion. Since this criterion defines the angular resolution it can be directly used for zoomable panoramas neglecting sensor sizes etc. By simply dividing the panorama <a href="Field_of_View.html" title="Field of View">Field of View</a> (FoV) by the angular resolution we get the maximum possible pixel resolution.
+<p>The maximum obtainable resolution is limited by diffraction according to the Rayleigh criterion<a class="external" href="http://www.wikipedia.org/wiki/angular_resolution">[*]</a>. We can safely assume the equivalent of one pixel distance as the minimum resolvable distance required by the Rayleigh criterion. Since this criterion defines the angular resolution it can be directly used for zoomable panoramas neglecting sensor sizes etc. By simply dividing the panorama <a href="Field_of_View.html" title="Field of View">Field of View</a> (FoV) by the angular resolution we get the maximum possible pixel resolution.
</p><p>For an average value we take the wavelength of light <i>��</i> = 550nm = 5.5*10<sup>-4</sup>mm which is in the middle of the spectrum and a color where our eyes are most sensitive. The resulting formula is:
</p>
<pre><img class="tex" alt=" pixel resolution = \frac{FoV}{asin\left(\frac{1}{1490*D}\right)}" src="5a12c95d04637539015c2d09b5002204.png" />
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</li><li>You will use an APS-C format sensor in portrait orientation for this panorama. A 800mm lens has a FoV of 1.1�� in that case, which at f/11 gives 2080 pixels or app. 6 megapixels. Applying the 70% rule to compensate for bayer interpolation blur indicates that 12 megapixels per image are enough.
</li></ul>
<a name="Wide_angle" id="Wide_angle"></a><h3> <span class="mw-headline">Wide angle</span></h3>
-<p>Although the above formula is applicable to wide angle and fisheye lenses as well it is harder to give correct values. Most DSLR wide angle and fisheye lenses change the entrance pupil diameter depending from the angle of incidence. This is intended and serves as a mechanism to compensate for natural <a href="Vignetting.html" title="Vignetting">vignetting</a>.
+<p>Although the above formula is applicable to wide angle and fisheye<a class="external" href="http://wiki.panotools.org/Fisheye">[*]</a> lenses as well it is harder to give correct values. Most DSLR wide angle and fisheye lenses change the entrance pupil diameter depending from the angle of incidence. This is intended and serves as a mechanism to compensate for natural <a href="Vignetting.html" title="Vignetting">vignetting</a>.
</p><p>However, diffraction is an issue for those lenses, too. For a comparison of two widely used fisheyes see <a href="Diffraction.html#External_links" title="Diffraction">link at the bottom</a>.
</p>
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</p><p>Other factors (lens shake, atmospheric scintillation, sensor noise, haze etc.) reduce resolution and sharpness even further, hence the above values will seldom be reached.
</p>
-<ul><li>wikipedia on Diffraction
-</li><li>wikipedia on Angular resolution
-</li><li>Ken Rockwell's page on Selecting the Sharpest Aperture
-</li><li>Ken Rockwell's page with a sharpness comparison of the Zenitar 16mm and Nikkor 10.5mm fisheye lenses at different aperture.
-</li><li>A very extensive article about resolution limits on Luminous Landscape containing many valuable links.
+<ul><li>wikipedia on Diffraction<a class="external" href="http://www.wikipedia.org/wiki/Diffraction">[*]</a>
+</li><li>wikipedia on Angular resolution<a class="external" href="http://www.wikipedia.org/wiki/Angular_resolution">[*]</a>
+</li><li>Ken Rockwell's page<a class="external" href="http://www.kenrockwell.com/tech/focus.htm">[*]</a> on Selecting the Sharpest Aperture
+</li><li>Ken Rockwell's page<a class="external" href="http://www.kenrockwell.com/zenit/zenitar-16mm.htm#sharp">[*]</a> with a sharpness comparison of the Zenitar 16mm and Nikkor 10.5mm fisheye lenses at different aperture.
+</li><li>A very extensive article about resolution limits on Luminous Landscape<a class="external" href="http://www.luminous-landscape.com/tutorials/resolution.shtml">[*]</a> containing many valuable links.
</li></ul>