Too small an image to see what you're referring to -- at least for my old yes. Let's see a wheel at 100%. 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.
