 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
| PhotoKB HomeDiscussion Groups Digital Photography Digital PhotoDSLR CamerasZLR CamerasPoint & Shoot CamerasFilm Photography 35 mmLarge FormatMedium formatDarkroomFilm and LabsOther EquipmentPhoto Technique Nature PhotographyPeople PhotographyTechnique GeneralGeneral Photo Topics General TopicsAustralian PhotographyUK PhotographyDirectoryPhoto Clubs |
Photo Forum / Digital Photography / DSLR Cameras / March 2006Calculating subject distance
Just a note to my fellow photographers. If you're ever taking a photograph of a helicopter and it comes so close you could almost touch it, cover up the camera and run! Don't do what I did yesterday and, like a total idiot, keep snapping the damn thing as it gets lower and lower, and drifts nearer and nearer to the car park. What was the reason I didn't even consider the down-wash until the thing was right over my head? It wasn't fun being directly beneath some large rotors that were that close. Luckily my lovely D70s didn't get injured, it was only my pride as I tried to shield myself, probably looking pretty stupid. Anyway, does anyone know of a technique to calculate how far the subject is away? I'd like to do this because I don't believe the helicopter should have been that low over a car park. I had my 300mm zoom set to maximum (don't ask why I did when the thing was so close - I think I was just panicking a bit so wasn't thinking straight! I have a nice shot of the rear seat passenger with his mouth open as if to say, "Oh my God there's someone there, get out the way!"). I guess maybe if I knew the size of the helicopter (I could guesstimate that) then I could look at the part of the helicopter in the frame, then aim the camera at something the same size on full zoom at a similar angle from me, then measure it's distance away? Is there a more scientific approach? I guess I could Google this one but I kinda wanted to mention what happened to you all so you can have a good laugh at my stupidity. :) Geoff. > Just a note to my fellow photographers. If you're ever taking a > photograph of a helicopter and it comes so close you could almost [quoted text clipped - 21 lines] > wanted to mention what happened to you all so you can have a good > laugh at my stupidity. :) Get your head out of the viewfinder. Helicopters can be very dangerous to people on the ground, and getting grit blown at you is only part of it. http://www.photo.net/photodb/folder?folder_id=230415 Cheers, Alan.  Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. > Get your head out of the viewfinder. Helicopters can be very dangerous > to people on the ground, and getting grit blown at you is only part of it. > > http://www.photo.net/photodb/folder?folder_id=230415 Nice photos Alan, particularly the red helicopter. I would never have stood under the helicopter intentionally but it did fairly quickly drift over towards me. Once I've got my nerve up to go back, I certainly won't be parking in that spot again. :) Geoff. >Get your head out of the viewfinder. Helicopters can be very dangerous >to people on the ground, and getting grit blown at you is only part of it. Particularly when they open up with the 20mm chain gun or shoot off a couple of Hellfires. ********************************************************** "A combat photographer should be able to make you see the color of blood in black and white" David Douglas Duncan Speaking on why in Vietnam he worked only in black and white http://www.hrc.utexas.edu/exhibitions/online/ddd/ SNIP > I guess maybe if I knew the size of the helicopter (I could > guesstimate that) then I could look at the part of the helicopter in [quoted text clipped - 3 lines] > but I kinda wanted to mention what happened to you all so you can > have a good laugh at my stupidity. :) It's not too hard to calculate. All you need is a known size of an object and the size of its image projected on the sensor (no.of pixels times sensel pitch). Multiply the Object/Image ratio (is the reciprocal of the magnification factor) with the focal length, and that's the distance. Assuming you don't need accuracy down to the inch, but rather to plus or minus a foot, you'll be close enough. Bart > I guess maybe if I knew the size of the helicopter (I could guesstimate > that) then I could look at the part of the helicopter in the frame, then > aim the camera at something the same size on full zoom at a similar angle > from me, then measure it's distance away? Is there a more scientific > approach? When trying to think of ways to answer the question "How far away from me is that helicopter?" is this really the first thing that comes to mind? Can you really not just look at the thing and know how far away it is? I guess I'm just a little confused as to how this could be difficult. SignatureJeremy | jeremy@exit109.com >> I guess maybe if I knew the size of the helicopter (I could guesstimate >> that) then I could look at the part of the helicopter in the frame, then [quoted text clipped - 6 lines] > Can you really not just look at the thing and know how far away it is? > I guess I'm just a little confused as to how this could be difficult. When there is a noisy helicopter right above your head, with incredible wind being generated by the rotors which is about to hit you, it's not too easy to think about how far away it is. It just happened once and caught me off-guard and scared the cr*p out of me, and at the time the last thought I had was how far away it was. I just knew it was damn close. lol. >> I guess maybe if I knew the size of the helicopter (I could guesstimate >> that) then I could look at the part of the helicopter in the frame, then [quoted text clipped - 6 lines] > Can you really not just look at the thing and know how far away it is? > I guess I'm just a little confused as to how this could be difficult. i hope he does not drive a car... >>> I guess maybe if I knew the size of the helicopter (I could guesstimate >>> that) then I could look at the part of the helicopter in the frame, then [quoted text clipped - 9 lines] > > i hope he does not drive a car... Hmmm....He does drive a car. See my previous post. Now I understand the fools who must drive at 70-80 mph only one car length behind a car (or worse, semi tractor-trailer) on the highway! They are not fools, they must be depth perception challenged! >Now I understand the fools who must drive at 70-80 mph only one car >length behind a car (or worse, semi tractor-trailer) on the highway! >They are not fools, they must be depth perception challenged! Well, they did it once before, and nothing happened, so obviously it is not dangerous! Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< >>>> I guess maybe if I knew the size of the helicopter (I could guesstimate >>>> that) then I could look at the part of the helicopter in the frame, [quoted text clipped - 13 lines] > > Hmmm....He does drive a car. See my previous post. has someone taught him to tell how far away the other cars are? |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.