diffraction
in [Digital Cameras]
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From: bugbear on 22 Dec 2009 04:23 egbert_no_bacon wrote: > On Dec 22, 1:11 am, "Charles" <charlesschu...(a)comcast.net> wrote: >> start here:http://www.luminous-landscape.com/tutorials/understanding-series/u-di... > > i would have said 'soft' after f8 > > so 'looking soft and lacking' is diffraction > And so are many other things. BugBear
From: Alex Monro on 22 Dec 2009 06:01 egbert_no_bacon wrote: > On Dec 22, 1:11 am, "Charles" <charlesschu...(a)comcast.net> wrote: >> start >> here:http://www.luminous-landscape.com/tutorials/understanding-series/u-di... > > i would have said 'soft' after f8 > > so 'looking soft and lacking' is diffraction Another detailed tutorial article, with on-line calculator: http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm
From: Martin Brown on 22 Dec 2009 06:29 egbert_no_bacon wrote: > On Dec 22, 12:26 am, "Jeff R." <cont...(a)this.ng> wrote: >> "egbert_no_bacon" <egbert_no_ba...(a)hotmail.co.uk> wrote in message >> >> news:59ce6c6d-8b34-48f3-aaea-04e69a04302a(a)v30g2000yqm.googlegroups.com... >> >>> what is diffraction, and do you have an example or know where an image >>> of such is posted for me to see please >> Here is one of mine from a few years ago:http://www.mendosus.com/armidale/uralla.jpg >> >> Nikon D50, f/22, 8 seconds, 24-120 zoom set at 24mm. >> Two frames poorly merged (but that doesn't matter). > > am i looking for here, what i would call 'air dust bubbles' in > daylight shots but 'light refection' as if a mirage, is this > diffraction The diffraction in that scene is the radial lines coming away from the bright streetlamps. The number and shape of the blades of the aperture mask determine the pattern. And the little spectra here and there are probably due to an internal reflection inside the lens. The air dust bubbles you describe are due to dust in the air being illuminated by the on camera flash. They are effectively point sources and very close to the lens and so out of focus. What the camera records is a disk with size roughly determined by geometrical optics with patterns inside it determined by the wave nature of light. > > i thank you To see diffraction for yourself stop down a lens way to a much smaller aperture with an aperture mask placed over the front of the lens. Nothing beats doing the experiment for yourself. The tradeoff is that at a smaller aperture you have greater depth of field, so you have to decide which matters most to you. You can also try a square or triangular hole too which will give bright rays off any strong point source or specular highlights in the field. Regards, Martin Brown
From: Ofnuts on 22 Dec 2009 07:18 On 22/12/2009 13:02, Better Info wrote: > > If the glass isn't diffraction limited at its largest aperture, then that > means it's not diffraction limited at ANY aperture. For some value of "largest". Are we taking about the "f-number" or about the actual aperture dimensions? -- Bertrand
From: Paul Ciszek on 22 Dec 2009 10:01
In article <hgpafg$gdv$1(a)news.acm.uiuc.edu>, Doug McDonald <mcdonald(a)scs.jllinois.edu> wrote: > >The diameter of a diffraction blur spot at f/x is about x/2 microns FWHM. I only know undergraduate physics type optics; is it possible to arrange a photograph with an "ordinary" camera that shows diffraction ripples as seen in physics textbooks? Or does diffraction in photography just take the form of a generic limit on sharpness? -- Please reply to: | "Any sufficiently advanced incompetence is pciszek at panix dot com | indistinguishable from malice." Autoreply is disabled | |