How can I have a 3-4 sec exposure in the daytime (raining)?

Discussion in 'Beyond the Basics' started by Treymac, Oct 12, 2009.

  1. Treymac

    Treymac TPF Noob!

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    Hey Rondal. Ya, I was thinking about it, and it makes sense. But my idea of 3-4 seconds is way off. The amount of time it takes a person to travel from one side of the frame to the other will be very short, maybe a second. So I'll have to trigger the flash at about half a second after the shutter. But the timing also changes according to proximity to me. Although if they are too far, and it takes 3-4 seconds to cross the frame, I won't see ghosting, since the shutter will be open for so long, the ghosting will pretty much disappear, and the only time the person will show up in the frame is when the flash hits them, in the middle of the frame.

    So my goal to get all this straight it to practice fully tomorrow with my digital camera and get things worked out, then on wednesday I'm going to take the actual shots on film.

    Also, would using a circular polarizer filter be enough to cut out light? If it does cut out enogh light, I think i'd like to use that instead to get an interesting look.


     
  2. Treymac

    Treymac TPF Noob!

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    I do have an external flash to mount in the hot shoe, it's a Vivitar 730AFC. I don't have a rear curtain flash, although I could probably borrow one from the class. Is your idea to shoot the external flash at the curtain?

    I don't know how receptive people would be to having a whole flash set up go off on them when they walk by though.
     
  3. Garbz

    Garbz No longer a newbie, moving up!

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    Crap I make this mistake all the time. In optics research we used filters which have either the stops or the dB but not the factor written on them. :(
     
  4. Actor

    Actor TPF Noob!

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    Assuming that the OP means "0.4 ND" when he writes "ND 4" then the attenuation is 1 1/3 stops. Perhaps the OP could clear that up.

    However, I get a feeling of deja vu here, as though sometime in the past I was told that 0.4 ND and ND 4 have different meanings. However, in my meager photography library (including catalogs) I find no mention of any other notation than that of preceding the "ND" with the "0.4" with the meaning given by Schaefer.
     
  5. FrankLamont

    FrankLamont TPF Noob!

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    ND filters are numbered by their attenuation factor... an ND 4 has 2 stops. Actor, you're probably referring to something else, yes.
     
  6. FrankLamont

    FrankLamont TPF Noob!

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    Ah, I see what you're trying to say. The filter optical density of a ND 2 is 0.3 -- but in terms of f-stops, it is one, whole stop.

    Even that, though, you're still wrong... he refers to 0.3, not 0.4.

    And even so... hmm, that's odd, it's either measured in stops of optical density... never knew you added it. Maybe that's just another way of titling it, still, never heard of it before.
     
  7. Treymac

    Treymac TPF Noob!

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    Hey guys. I have a ND4 filter, 0.6 density.

    I've found information on it at wikipedia: Neutral density filter - Wikipedia, the free encyclopedia
     
  8. FrankLamont

    FrankLamont TPF Noob!

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    Precisely, though a ND2 has 0.3 density -- half of that, which was what I was referring to if you re-read my post. :)
     
  9. RONDAL

    RONDAL TPF Noob!

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    your distance to subject and focal length will determine how long it takes for a person to cross the frame. this theoretically could be shot with like a 50mm (crop or non-crop body) from the other side of the street. Would take a person about 5 seconds to cross the frame at that distance and focal length.

    either with a handheld flash (offcamera) or a lightstand somewhere, you could trigger your flash using a wireless trigger, or a voice activated assistant.

    I am actually tempted to try this out myself and see how it turns out. The idea i have in my head is prolly very different to the one you have but it might be cool.
     
  10. Treymac

    Treymac TPF Noob!

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    I'm still trying to decide on the best day for this, it's apparently going to rain really hard the next couple of days. Maybe I'll just take an umbrella. :D

    My second idea is related, but what I want to do is have a very long exposure in the daylight, so much so that no person or car will show up in the photo. I'm going to pair my ND filter with my polarizer to get the long exposure. This is to make the streets look dead and desolate; the only things in the picture will be statues, buldings, roads, and other structures. But it just occured to me that cars are going to have day time running lights, which will show up in the picture.

    Is there anything I can do about this? Would car lights show up less when the sky is clear and the sun is out, compared with overcast and raining?
     
  11. RONDAL

    RONDAL TPF Noob!

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    if you do a long exposure at day you are going to get hotspots all over the place. and you will likely get a haze where all the ppl are walking.
     
  12. CraniumDesigns

    CraniumDesigns TPF Noob!

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    use the lowest iso possible, the smallest aperture, and if u need MORE exposure time, use an ND filter. those are the only methods i know to lengthen exposure time.
     

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