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Diffraction limited pixels... Really?
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<blockquote data-quote="dslater" data-source="post: 363300" data-attributes="member: 32537"><p>Shame on you for bringing the practical realities of real world photography to a theoretical discussion of DOF <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" />. You are of course correct, there are many more variables than DOF & aperture. Your previous post is also correct about the difficulties of making this calculation for a real lens without the manufacturers data. However, in that case, you have a much easier option - namely testing. All you need is a good tripod, good technique, and a convenient brick wall. Put the lens on you interested in. Set up you camera on the tripod, making sure the sensor plane is exactly parallel to the wall, and make test shots at various F-stop values. ( don't forget to use your mirror lockup and electronic first curtain if available to remove camera shake. ) <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p><p></p><p> You can vary the distance to the wall, but I think that usually, with the exception of special lenses like macro lenses, the optimum f-stop will not change much with distance to the subject. On the other hand, if you have a zoom lens, you will need to test at a variety of focal lengths as the optimum f-stop does tend to change with focal length on a zoom lens.</p><p></p><p>For anyone who's interested, this site lets you see how the airy disk of a perfect lens compares to pixel size for a number of cameras. </p><p></p><p><a href="http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm" target="_blank">Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks</a></p></blockquote><p></p>
[QUOTE="dslater, post: 363300, member: 32537"] Shame on you for bringing the practical realities of real world photography to a theoretical discussion of DOF :). You are of course correct, there are many more variables than DOF & aperture. Your previous post is also correct about the difficulties of making this calculation for a real lens without the manufacturers data. However, in that case, you have a much easier option - namely testing. All you need is a good tripod, good technique, and a convenient brick wall. Put the lens on you interested in. Set up you camera on the tripod, making sure the sensor plane is exactly parallel to the wall, and make test shots at various F-stop values. ( don't forget to use your mirror lockup and electronic first curtain if available to remove camera shake. ) :) You can vary the distance to the wall, but I think that usually, with the exception of special lenses like macro lenses, the optimum f-stop will not change much with distance to the subject. On the other hand, if you have a zoom lens, you will need to test at a variety of focal lengths as the optimum f-stop does tend to change with focal length on a zoom lens. For anyone who's interested, this site lets you see how the airy disk of a perfect lens compares to pixel size for a number of cameras. [url=http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm]Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks[/url] [/QUOTE]
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