On Mon, October 12, 2009 11:46, ADavidhazy wrote: > > I'm amused at the use of quotes around "grading" :-). > > Yup ... I've "developed" this strategy for a number of reasons. Most too > obscure and without pedagogical (!!!) merit. OTOH I have been "grading" > my classes in a similar way for many years and I probably am not going to > change to a more conventional "point" system as most of my fellow > intructors use. My grading is more psychological than numerical. Looks like I'm teaching my second course at a local community college this spring, so "exercises" and "tests" and "grading" are on my mind even more than usual right now. > > Was the Lartigue reference to his photo of car No. 6 in a race? That's > > what I think of as the most famous photo "exploiting focal-plane > shutter > > distortion", and it's by him, but I don't know if that's what you were > > thinking of. > > Yes. When the "lecture" about FP shutters was given the Lartigue > photogrpah > was mentioned. It was not shown though. Will there be initiative on > student's part? Who knows. I had to look it up to be sure it really was him; I remembered the photo as being the canonical example, though, so searching on his name and scanning for the photo I remembered worked pretty quickly. The Internet makes me smarter! :-) (I've never actually taken a course on photography; I was a math major, and my career has been in computers, which I started 3 years before I went to college.) > > I'm not at all clear what's going on in #27, either. > > The highlights of the bullet make a "blur" on the "wrong" side of the > bullet. > "Speed lines" as drummed into our heads by illustrators should trail a > moving > subject and not lead it. But as the flash falls off in output the > highlights of > the bullet reflect useful light for a longer time than the shadows and as > the > light level is dropping the bullet is moving forward and so one ends up > with blur on the wrong side. Thanks, much clearer. Part of the problem was just that I don't have much familiarity with high-speed photos below the "art" level of clarity, so I was having some trouble being sure I even knew what bits were what in that photo (though I did in fact identify the bullet correctly, as it turns out). No doubt having actually taken your course would have made this test considerably easier :-). > > Another question brings up a question I've had for years about sound > > triggers: Where can one buy one? I've never seen anything closer than > a > > kit. I might still be able to put an electronic kit together and make > it > > work. > > Well, I usually use a tape recorder that on detecting sound triggers a > sensitive gate SCR which fires the flash. I've also recently built one > based on an integrated circuit audio amplifier but when I made a second > one > patterend after the first one it failed to perform - frustrating. > > http://people.rit.edu/andpph/text-cheap-sync.html > http://people.rit.edu/andpph/text-audio-sync-circuit.html > http://people.rit.edu/andpph/text-PC-flash-sync-socket.html The perversity of inanimate objects continues to reign, yes! > I can sugggest two commercial sources you may want to look into. > > www.quaketronics.com sells a nice unit for about $100 > www.hiviz.com (associated with Lauren Winters of NC High School of Science > I > believe) sells kits at quite reasonable proces. Thanks. Those look potentially very useful. And the electronics are at the level where I actually understand everything he's saying, though I couldn't have designed them myself. Theory is actually of some use sometimes! The Quaketronics looks particularly useful, because for lots of people I know, their hobby is photography and not electronics; especially people who started in the digital era, lots of them just aren't into hardware tinkering. Being able to buy something assembled in a decent case is highly desirable. I'm still interested in making it trigger the shutter instead of a flash (for slower things -- one of them is catching empty brass in flight from guns, for example; a friend does commercial work in this area and currently is getting his flying brass by random luck with the modestly high frame-rates of modern cameras). But an SCR might well be something that could be wired into a Nikon 10-pin cable? One of these years I'm not going to be able to resist this anymore. Pellet guns make a lot of the classic bullet pictures doable in convenient settings at home. -- David Dyer-Bennet, dd-b@xxxxxxxx; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info
