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  1. #1

    getuptogetdown's Avatar
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    DSLR + dark shot w/ LED light
    Hi everyone...I am new to the use of DRLR and i was experimenting with holding an LED light in a pitch black room and putting my camera on a tripod and opening then lens for about 10 seconds. It looks cool and I can write because it absorbs all that light...but it is extremely out of focus....how do i go about fixing this so its in focus?

    thanks!
    Loving my MBP more and more everyday

  2. #2

    lifeafter2am's Avatar
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    The easiest way is to usually set the aperture as low as it will go, this will make much more of the shot in focus (f/22 or something like that). Normally you would need a longer shot for this, but with light-writing it's not usually a problem.

    Also, try and pre-focus on something with the light on.
    masakatsu agatsu

    @lifeafter2am

  3. #3

    BlueMac's Avatar
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    Aperture is simply the size of the hole that lets the light in, it won't directly affect the focus. Put an object right where you will be standing, and focus (of course you should have the light on. Then open shutter and shoot. Good luck.


    Can you provide us with the result, too?
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  4. #4

    lifeafter2am's Avatar
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    Quote Originally Posted by BlueMac View Post
    Aperture is simply the size of the hole that lets the light in, it won't directly affect the focus. Put an object right where you will be standing, and focus (of course you should have the light on. Then open shutter and shoot. Good luck.


    Can you provide us with the result, too?
    ARE YOU KIDDING??? Aperture affects the DOF, with a smaller aperture there is a large DOF, which in turn gives a larger range of focus. Which in this case is perfect because there is no exact location for focus.
    masakatsu agatsu

    @lifeafter2am

  5. #5

    BlueMac's Avatar
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    Quote Originally Posted by lifeafter2am View Post
    ARE YOU KIDDING??? Aperture affects the DOF, with a smaller aperture there is a large DOF, which in turn gives a larger range of focus. Which in this case is perfect because there is no exact location for focus.
    Shutter speed is more dominant with DOF. However, he is attempting to have an even focus, so DOF won't matter here.

    OP:
    Set your focus range to infinity, lowest focal length. Mess around with different aperture and shutter speed combos... you will see for yourself what different combos look like, and witness it all firsthand.
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    Si, hablo Espa˝ol. Oui, je parle franšais. Yes, I speak English.

  6. #6

    lifeafter2am's Avatar
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    Quote Originally Posted by BlueMac View Post
    Shutter speed is more dominant with DOF. However, he is attempting to have an even focus, so DOF won't matter here.

    OP:
    Set your focus range to infinity, lowest focal length. Mess around with different aperture and shutter speed combos... you will see for yourself what different combos look like, and witness it all firsthand.
    Not to argue with you here, but you are dead wrong. I shot professionally for a number of years, DOF has nothing to do with shutter speed, except that the aperture controls what shutter speed you use. I would be more than happy to provide 100's of articles that state this. Shutter speed controls stopping of action, motion blur, etc, but does not control the actual depth of field, that is all aperture.

    Aperture and Depth of Field (DOF)

    We mentioned this above but feel it is important enough to repeat in its own paragraph.

    The Depth of Field is the distance wherein objects are in focus.

    There are times when you desire a great depth of field, i.e. where objects both close to you and far from you are in focus. This is especially true when you are taking a landscape picture and want as much as possible to be in crisp focus.

    Then there are times when you want to isolate your subject, as when you are taking a portrait and want your subject to be in sharp focus but the background to be out of focus. In this case, you desire a shallow depth of field.

    One way to influence DOF is by selecting the appropriate aperture.

    The rule of thumb is this:

    Select a large aperture (or small f/value or small aperture value), e.g. f/2.8, to obtain a shallow DOF
    Select a small aperture (or large f/value or large aperture value), e.g. f/8.0, to achieve great DOF
    masakatsu agatsu

    @lifeafter2am

  7. #7

    AConfire's Avatar
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    Quote Originally Posted by lifeafter2am View Post
    Not to argue with you here, but you are dead wrong. I shot professionally for a number of years, DOF has nothing to do with shutter speed, except that the aperture controls what shutter speed you use. I would be more than happy to provide 100's of articles that state this. Shutter speed controls stopping of action, motion blur, etc, but does not control the actual depth of field, that is all aperture.
    Lifeafter2am is completely right.

    Also, don't set your focus to infinity. If the lights are going to be 5 feet away from you, they'll be out of focus.

    Pre-focus on the area that you will be shining the light, then set your shutter speed for whatever time you need to shine the light, and you're done.


    View my photography blog Here!

  8. #8

    getuptogetdown's Avatar
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    Even though you say not to do this...how do i go about setting my focus to infinity anyways??

    And...I tried setting my aperture as high as i could with a 10 second shutter speed and also tried focusing on the light i would be holding (its a flashing ball), and the image is still coming out really blurry.
    Loving my MBP more and more everyday

  9. #9

    Village Idiot's Avatar
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    Use f/11. If you use the smallest aperture, then it can cause IQ issues. Prefocus with a broom or something. Regardless of what camera you own, you should be able to set the AF to a seperate button. That or focus on where you're going to be writing and turn the AF off so when you press the shutter halfway down, the camera doesn't try to AF.

    Post some examples up. It really helps us help you if we're seeing why your pictures are turning out crappy.
    Chaotic Evil, Level 1 IT-Tech

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  10. #10


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    focus the lens with the room light on, flick the switch over to manual focus, turn the room light off, turn on your led light, take the shot

  11. #11

    getuptogetdown's Avatar
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    Still can't get a great shot...I will try to post a picture in the next day or so
    Loving my MBP more and more everyday

  12. #12

    Dysfunction's Avatar
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    Quote Originally Posted by lifeafter2am View Post
    Not to argue with you here, but you are dead wrong. I shot professionally for a number of years, DOF has nothing to do with shutter speed, except that the aperture controls what shutter speed you use. I would be more than happy to provide 100's of articles that state this. Shutter speed controls stopping of action, motion blur, etc, but does not control the actual depth of field, that is all aperture.
    Whew.. thank you for seeing this earlier
    mike
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  13. #13

    Village Idiot's Avatar
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    Quote Originally Posted by lifeafter2am View Post
    Not to argue with you here, but you are dead wrong. I shot professionally for a number of years, DOF has nothing to do with shutter speed, except that the aperture controls what shutter speed you use. I would be more than happy to provide 100's of articles that state this. Shutter speed controls stopping of action, motion blur, etc, but does not control the actual depth of field, that is all aperture.
    Sensor size, focal length, and relative distances all play a factor in DOF.
    Chaotic Evil, Level 1 IT-Tech

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  14. #14

    lifeafter2am's Avatar
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    Quote Originally Posted by Village Idiot View Post
    Sensor size, focal length, and relative distances all play a factor in DOF.
    Correct, but not shutter speed. lol.
    masakatsu agatsu

    @lifeafter2am

  15. #15

    Dysfunction's Avatar
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    Quote Originally Posted by Village Idiot View Post
    Sensor size, focal length, and relative distances all play a factor in DOF.
    and all are really only relevant in comparison to aperture.
    mike
    This machine kills fascists
    Got # ? phear the command line!

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