Long Exposures

Discussion in 'Digital Photography' started by SB123, May 17, 2011.

  1. SB123, May 17, 2011
    Last edited: May 17, 2011

    SB123 macrumors member

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    #1
    I'm rather new to photography and the other thread got me thinking. Why can't I take a long exposure photo? I have a Nikon D60 and I'm using the 18-55 mm 1:3.5-5.6 lens that came with it. I understand that the shutter will be open longer so the aperture needs to be as small as possible (higher #) to reduce the light.

    If I set the shutter speed to 2 seconds, I can't get the aperture above f36. The photo is always over exposed.

    Is this because of the camera or the lens or something I am missing? Would a higher or lower ISO help?
     
  2. Grey Beard macrumors 65816

    Grey Beard

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    #2
    Yep a lower ISO is the other setting to factor in. What were you using.
    KGB
     
  3. SB123 thread starter macrumors member

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    #3
    It was at 800, but I've tried lower and still can't get the aperture right.
     
  4. LittleCanonKid macrumors 6502

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    #4
    How dark are the conditions you're trying to shoot in? If you're trying to pull of long exposures in broad daylight, you're going to need an ND filter. Low ISO and stopped down apertures combined can't shut out daylight completely.
     
  5. The Mad Kiwi macrumors 6502

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    #5
    To do long exposures in daylight you'll need a 10 stop nd filter like the Hoya ND400.
    They're almost black glass you can just barely see through the viewfinder for framing, remember to cover the viewfinder during exposure otherwise you'll get some light spill to the sensor through it.
    You'll also need to do a custom colour balance as the 10 stop filters don't block the spectrum evenly, hence you see lots of b&w or desaturated long daytime exposures.
    Good luck they're lots of fun.
     
  6. SB123 thread starter macrumors member

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    #6

    I tried shooting during the day and that obviously didn't work. So I tried at dusk on a cloudy day and the pics were still over exposed.

    Does the camera or lens limit how much you can stop down the aperture?
     
  7. SB123 thread starter macrumors member

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    #7
    I didn't know that light can get to the sensor through the viewfinder. How do you cover it?
     
  8. emorydunn macrumors 6502

    emorydunn

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    #8
    It's not much light but light can go both ways (from lens to viewfinder and viewfinder to lens). For example, if you look into a lens on a Canon 7D when all the auto-focus points are lit up you can see a red glow.

    A piece of gaffer's tape will do. Or really fancy cameras (Canon 1D) actually have a built in slide to cover the viewfinder.
     
  9. VirtualRain, May 17, 2011
    Last edited: May 17, 2011

    VirtualRain macrumors 603

    VirtualRain

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    #9
    I believe there is some misconception here about light bleed from the viewfinder. Light from the viewfinder can only affect metering before a shot... Best practise thereby suggests covering the viewfinder when relying on auto metering/exposure when not looking through the viewfinder (remote shutter release). Once the mirror flips up to expose the shot on the CCD, the light path from the viewfinder is blocked for you, and you can take your eye away without impacting the exposure.

    Check out this video to see what's going on... http://www.youtube.com/watch?v=FWM7Ma9qLvc

    For long exposures in bright light, you will need a neutral density, polarizer, or some other filter to help you reduce the amount of light. A small aperture is not always enough in bright light. According to the sunny 16 rule, at ISO 100 in bright daylight you need f/16 for 1/100th shutter... which is 8 stops away from 2 seconds. The only way to reduce the light that much is with a filter.
     
  10. compuwar macrumors 601

    compuwar

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    #10
    The smallest aperture is decided by the construction of the lens- however apertures beyond about f/16 on your camera are going to produce blurry images due to diffraction. You need to shoot at low ISO and use a neutral density filter if it's not dark enough for the exposure you want. You can stack ND filters in the right holder. The Lee Gelsnap ND filter kit is a good relatively cheap starting point.


    Sorry, but this is incorrect, light will leak in through the viewfinder, around the mirror and spoil a long exposure on lots of camera bodies. While the viewfinder can affect metering before a shot, it can also allow light to leak around the mirror during very long exposures.

    See for example:

    http://www.wonderhowto.com/how-to-use-your-viewfinder-cover-avoid-spray-light-with-nikon-d3-378259/

    Paul
     
  11. Ish macrumors 68010

    Ish

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    #11
    Apologies for asking, but you are shooting on manual aren't you?
     
  12. SB123 thread starter macrumors member

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    #12
    yes
     
  13. SB123 thread starter macrumors member

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    #13

    So if I were to get a better lens, it would still be limited by the camera? Is this correct?

    I'll give a filter a try. Thanks all.
     
  14. TheReef, May 18, 2011
    Last edited: May 18, 2011

    TheReef macrumors 68000

    TheReef

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    #14
    Switch your camera to aperture priority and dial the aperture in to the largest value - f/36 in your case.
    Take a read of the shutter speed - that is the slowest you can go in that situation to obtain a correct exposure.
    Any slower than this speed your images will become overexposed, because you are letting in more light (more time) than required for a correct exposure.

    Buying a "better" lens won't fix your problem - better lenses aren't usually defined by how much you can stop them down, it's quite the opposite.
    "Better" is a loose term, but a better lens will usually have a wider maximum aperture that will let more light in - eg f/2.8

    Your camera is fine, it's a trait of all cameras/lenses, it's best not to stop down past f/16.
    Diffraction is a natural phenomena where light bends, there is no escaping it :)
    Hold your finger up to your eye and look at a sharp edge (the edge of your monitor will work as it has good contrast with the screen), you will notice the edge "bend" around your finger (focus on the screen edge, not your finger).
    The same thing happens with your camera - when the aperture hole is small, all light entering is close to the edge of the aperture blades and so will bend/interfere resulting in a softer image.


    Buying Neutral Density filters is really the only practical way of solving your problem.

    I'd recommend a filter holder, so you can stack multiple filters, eg a ND and a ND Grad. I'd also suggest a graduated ND to darken the sky.

    Good luck! :)
     
  15. SB123 thread starter macrumors member

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    #15

    This makes total sense. Thanks for your response.
     
  16. compuwar macrumors 601

    compuwar

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    #16
    No, aperture is limited by the lens- it's the ratio of the size of the diaphragm to the focal length of the lens, however anything shot at f/32 is going to suck due to diffraction.

    Paul
     
  17. Artful Dodger macrumors 68020

    Artful Dodger

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    #17
    Just to help a bit, if you look in your camera box, you should have a view "cover" to slip over the area open that could let in a bit of light. I'm saying this because all my Nikons have had this come with them and even state so in the manual. You will have to find it as it should be somewhere in the box or it was taped to something and hopefully it didn't get tossed thinking it was some extra small piece of packaging plastic.
    Good luck :D
     

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