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Thread: ND4 and ND8

  1. #1

    Default ND4 and ND8

    i am thinking of buying ND filter to create some super long exposure.

    ve some doubts to clear.

    1. ND4 is 2 stops, ND8 is 4 stops, correct?

    2. exposure calculation after puttin on ND8

    in aperture priority, scene requires 20 sec at F8 (w/o filter)

    so, after puttin on filter, exposure is 20 x 2 x 2 x 2 x 2 = 320 sec, rite?

    3. any other advise is much welcome.

  2. #2
    Senior Member
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    Default Re: ND4 and ND8

    1. ND4 is 2 stops, ND8 is 4 stops, correct?
    wrong, ND8 is 3 stop... they go buy power of 2 and not multiple

    2. exposure calculation after puttin on ND8
    in aperture priority, scene requires 20 sec at F8 (w/o filter)
    so, after puttin on filter, exposure is 20 x 2 x 2 x 2 x 2 = 320 sec, rite?
    3stops down... 160s f8 or 20s f2.8... 320s is correct if ND8 is 4stops(ND16)

    3. any other advise is much welcome.
    Last edited by ExplorerZ; 26th August 2008 at 11:31 PM.

  3. #3
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    Default Re: ND4 and ND8

    I wish i could help and i too wanted to ask the questions. Thanks for asking first, Attap Seed.

    I think this is a place where fellow CSers can help to point out or advice others with their experience rather than asking them to read up. Remember that we were all newbies once. We were not born with a photography implant. Newbies who ask questions can also be experts in other fields.

    There are many good patience photographers, one of them is night86mare and YouHong. I have benefitted from their guidnace. I am sure they and others will gladly share when others exhibit less of a patience.
    Don't brag about your accomplishments; Show us your future works.

  4. #4

    Default Re: ND4 and ND8

    actually can goggle, but i jus lazy.

    ok, now i know, ND4 is 2 stop, ND8 is 3 stops.

    many thanks!

  5. #5
    Moderator catchlights's Avatar
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    Default Re: ND4 and ND8

    2x = one stop
    4x = two stops
    8x = three stops
    16x = four stops
    32x = five stops
    64x = six stops
    Shoot to Live, Live to Shoot
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  6. #6
    Senior Member giantcanopy's Avatar
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    Default Re: ND4 and ND8

    There are various nomenclature for stating the density of filters. As defined by Kodak in 1940s, a filter can be represented by its density ( n = 2^f ), f stop, transmission ( percentage ), the opacity

    For example -

    NDn absorbs f stop, 1/n ( 100/n% ) transmission, ND ( 3f/10 )

    ND2 absorbs 1 stop , 1/2 ( 50% ) transmission, ND 0.3

    ND4 absorbs 2 stops, 1/4 ( 25% ) transmission, ND 0.6

    ND8 absorbs 3 stops, 1/8 ( 12.5% ) transmission, ND 0.9

    and so on and so forth

    ND400 translates to 8 2/3 stops, 0.25% transmission, ND 120

    Makers do not have a standard for labelling their items. Singh Ray refers them by stops to cut confusion across. Lee and Tiffen refers them as 0.3, 0.6 ( for one and two stops ) The use of ND 2 / ND 0.3 can be rather confusing at times, do check out what exactly you are buying before hand

    Ryan

  7. #7

    Default Re: ND4 and ND8

    ok, thks.

    i jus lookin at the basic hoya ND8.

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