<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>_paulc</author><text>Long time since I did any optics but this basically just convolution. The impact at the output plane of dust&amp;#x2F;imperfections on the lens is (approximately) a 2D fourier transform of the dust&amp;#x2F;imperfections. If you have a single dust particle (essentially an impulse) on the lens this will be convolved into a dc response at the focal plane.&lt;p&gt;[1] &lt;a href=&quot;http://en.wikipedia.org/wiki/Fourier_optics#Fourier_transforming_property_of_lenses&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Fourier_optics#Fourier_transfor...&lt;/a&gt;</text><parent_chain></parent_chain></comment><story><title>Dirty lens article</title><url>http://kurtmunger.com/dirty_lens_articleid35.html</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>nakedrobot2</author><text>The wider the lens, the more dust on the front element affects the picture. Especially specular light (bright light sources, especially the sun).&lt;p&gt;If you have a very wide-angle or fisheye lens (e.g. gopro) then you will most certainly have lots of nastiness in your photo from having a dirty lens.&lt;p&gt;You&amp;#x27;ll notice that in this person&amp;#x27;s test shots, he has no specular light or sunlight in the images. If he did, the test would have had completely different results.&lt;p&gt;If you have a gopro, try it yourself. Have a dusty or greasy lens and take a picture with&amp;#x2F;without the sun in it and the photo will certainly be worse.&lt;p&gt;Same with my mobile phone - if the front glass is greasy, well, of course the photo looks much, much worse.&lt;p&gt;I&amp;#x27;m a professional photographer specializing in 360º imagery shot with fisheye lenses, so I know this stuff very well from experience.</text><parent_chain></parent_chain></comment><story><title>Dirty lens article</title><url>http://kurtmunger.com/dirty_lens_articleid35.html</url></story>