On Dec 23, 2010, at 11:49 PM, paul stenquist wrote: > Too small an image to see what you're referring to -- at least for my old > yes. Let's see a wheel at 100%.
That would be for my ole eyes. > Paul > On Dec 23, 2010, at 10:39 PM, Doug Franklin wrote: > >> OK, I know there are some folks around the list that know a lot more about >> the physics, optics, and other science surrounding our hobby than I do. And >> I'm asking their help in understanding something. >> >> In the following photo, take a specific look at the way that the wheels and >> in particular the spokes are rendered. It's a digital capture, but I've >> seen the same effect in film captures. >> >> http://www.facebook.com/photo.php?fbid=119672688098162&set=a.114665221932242.11964.100001662949948 >> >> Specifically, notice that the spokes, especially on the rear wheel, appear >> mostly as blurs of grey. But also notice that there are specific highlights >> that look like slightly blurry spokes themselves. The number of these >> artifacts in the photo is identical to the actual number of spokes on each >> wheel. I specifically checked after having noticed this effect in previous >> shots. >> >> But I don't understand how they get there. I'm suspecting is some sort of >> "temporal moire" thing going on, but I can't envision the mechanism. And >> that's the help I'm asking. I'm hoping one of you can explain the physical >> mechanism that's leading to those blurry spokes in the wheel instead of just >> showing a less "peaked", more uniform grey blur. >> >> The shutter speed was 1/250, which is intentionally slow enough to give the >> wheels and background a blur while giving me a chance to get a sharp shot of >> the body while panning (I shoot almost all of the moving car shots on the >> track at 1/250, if you can see the wheels in the shot; 1/125 if it's a slow >> corner). The car was going about 100 miles an hour and accelerating as the >> shot was taken. >> >> -- >> Thanks, >> DougF (KG4LMZ) >> >> -- >> PDML Pentax-Discuss Mail List >> [email protected] >> http://pdml.net/mailman/listinfo/pdml_pdml.net >> to UNSUBSCRIBE from the PDML, please visit the link directly above and >> follow the directions. > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
