tag:blogger.com,1999:blog-22301740.post2125917893802189066..comments2024-03-18T06:17:20.604-07:00Comments on The Scratching Post: What Can You See In The Waters Of Lake Murray?K T Cathttp://www.blogger.com/profile/10259428595745509790noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-22301740.post-21211981078526386732012-03-23T14:29:43.573-07:002012-03-23T14:29:43.573-07:00Yeah, it's not the focal length that's the...Yeah, it's not the focal length that's the issue, it's the suspended particles in the water.K T Cathttps://www.blogger.com/profile/10259428595745509790noreply@blogger.comtag:blogger.com,1999:blog-22301740.post-50540501330141590852012-03-23T11:17:44.271-07:002012-03-23T11:17:44.271-07:00OK, not as bad as it might be, but the manual says...OK, not as bad as it might be, but <a href="http://resources.kodak.com/support/pdf/en/manuals/urg01105/PLAYSPORT_Zx3_xUG_GLB_en.pdf" rel="nofollow">the manual</a> says that the minimum focus distance underwater is 4.4 feet, as compared to 3.3 feet in air.tim eiselehttp://somethingscrawlinginmyhair.comnoreply@blogger.comtag:blogger.com,1999:blog-22301740.post-40300435621304672142012-03-23T10:24:08.213-07:002012-03-23T10:24:08.213-07:00Then again, that depends on whether the lens is ac...Then again, that depends on whether the lens is actually in contact with the water, or whether there is a flat piece of protective glass in front of the lens. If there's a flat glass window, with air between it and the lens, then it should have the same focal length underwater as in air.tim eiselehttp://somethingscrawlinginmyhair.comnoreply@blogger.comtag:blogger.com,1999:blog-22301740.post-55009981723306767032012-03-23T10:19:35.291-07:002012-03-23T10:19:35.291-07:00Something that just occurred to me about the focal...Something that just occurred to me about the focal length: lenses depend on the difference in refractive index between the lens and the medium - and water's refractive index is a lot closer to that of glass than air's is. There's still air behind the lens, so it will half-work, but in water the lens is going to have a significantly longer focal length because the light won't be bent as much as it should coming into the lens[1].<br /><br />So if the camera can normally focus on stuff 3 feet away, under water its closest focus might be increased to as much as 6-8 feet. So five feet away wouldn't be far enough, and in that case your camera was just too close to the reeds to focus!<br /><br />[1] My brother is crazily nearsighted (20/200 vision), but he says that when he's swimming and opens his eyes underwater, his vision is almost 20/20.tim eiselehttp://somethingscrawlinginmyhair.comnoreply@blogger.comtag:blogger.com,1999:blog-22301740.post-45473421443094333302012-03-23T09:43:00.633-07:002012-03-23T09:43:00.633-07:00Tim, I thought the same thing. The sediment is coa...Tim, I thought the same thing. The sediment is coarse sand, save for the floating particulates, apparently. The sand just sat there when I placed the camera. My next experiment will be to place it in a running stream. At least the water motion will be interesting.<br /><br />As for the microphone, it does fine. There just no noise in the lake.K T Cathttps://www.blogger.com/profile/10259428595745509790noreply@blogger.comtag:blogger.com,1999:blog-22301740.post-52871053335447422102012-03-23T07:03:07.882-07:002012-03-23T07:03:07.882-07:00Huh. The water didn't look that muddy until af...Huh. The water didn't look that muddy until after it went under. Was there just enough mud to mess with the autofocus, so that when there were actual objects present it couldn't focus on them? Maybe it would be possible to lock the focus at a particular distance to cure that.<br /><br />I thought at first that it was going to be a good hydrophone, at least, but then the sound cut out. Does the microphone stop working when it completely fills with water?tim eiselehttp://somethingscrawlinginmyhair.comnoreply@blogger.com