Nuetral Density Filters

Discussion in 'Digital Photography' started by HomeingPigeon, Aug 12, 2008.

  1. HomeingPigeon macrumors regular

    Joined:
    Aug 1, 2007
    #1
    I am looking to buy one. Is there a difference though between a 0.6 and a 0.9 filter? If there is can you tell me what it is?
     
  2. flinch13 macrumors regular

    Joined:
    Jul 4, 2004
    #3
    I could be completely wrong, but I think the .9 is one stop stronger than the .6.
     
  3. Westside guy macrumors 601

    Westside guy

    Joined:
    Oct 15, 2003
    Location:
    The soggy side of the Pacific NW
    #4
    There may be some rationale in the numbering system that I've just somehow managed to miss; but my impression has been that what label translates to what degree of light blockage depends on the brand. So... what brand are we talking about?
     
  4. kitmos macrumors newbie

    Joined:
    Jul 10, 2007
    #5
    The .6 is the most useful to start with. Only if this isn't strong enough try the .9.
    I have no idea how they came up with the numbering system
     
  5. RainForRent macrumors 6502

    RainForRent

    Joined:
    May 31, 2006
    Location:
    Greenville, SC
    #6
    Neutral density may be one of the most useful filters in color photography.
     
  6. Westside guy macrumors 601

    Westside guy

    Joined:
    Oct 15, 2003
    Location:
    The soggy side of the Pacific NW
    #7
    Okay, dug around on B&H's site...

    0.3 = 1 stop
    0.6 = 2 stops
    0.9 = 3 stops

    I like B+W's numbering system better: #103 is a 3 stop filter, #106 is six stops, etc. Easier to know exactly what you're buying.
     
  7. HomeingPigeon thread starter macrumors regular

    Joined:
    Aug 1, 2007
    #8
    Ok thanks everyone. Westside Guy... I was really talking about any specific brand but more just generally what does it mean.

    Thanks again.
     
  8. Westside guy macrumors 601

    Westside guy

    Joined:
    Oct 15, 2003
    Location:
    The soggy side of the Pacific NW
    #9
    Well, just as in other areas of photography a "stop" refers to a doubling of light in terms of exposure. If you put a two-stop ND filter on your lens, it means you can expose that particular photo two stops higher than if you didn't have the ND filter on your lens. So you can use two stops larger aperture (e.g. f/2.8 instead of f/5.6) OR two stops longer exposure (e.g. 1/2 second instead of 1/8 second) OR two stops higher ISO setting (e.g. ISO 800 instead of ISO 200) OR any combination of adjustments that adds up to two stops total.
     
  9. ChrisA macrumors G4

    Joined:
    Jan 5, 2006
    Location:
    Redondo Beach, California
    #10
    The amount of light transmitted by the filter is "10 to the minus d" where d is that number .6 or .9 It's hard to format a math formula here but it is like this: t = 10^-d
    where "t" is the fraction of transmitted light and d is that number .3, .6 or whatever

    So, a .3 filter transmits 1/1000th of the light, a .6 1/1000000 and a .9 transmits 1/1000000000

    Notice that the number of zeroes equals the number after the decimal point

    So now if you want to turn a 1/1000th second exposure into a 1 second exposure use a .3 ND filter. and a .6 filter wold allow a 1000 second exposure. But watch it with those ultra long exposure times you will get noise in the image even at low ISO. It's what they call "thermal noise" the cause is that the sensor is slightly sensitive to heat (and of course very sensitive to light) But when you use an ND filter that cuts the light by 1/100000000 the heat is not cut and relative to the light is now a billion times stronger.

    It is explained very clearly here
    http://en.wikipedia.org/wiki/Neutral_density_filter
     
  10. Westside guy macrumors 601

    Westside guy

    Joined:
    Oct 15, 2003
    Location:
    The soggy side of the Pacific NW
    #11
    It's an odd numbering system. It doesn't look like something designed by a photographer, since photographers tend to think in terms of "stops" - which is a relative, not absolute term; and is based on powers of 2 not 10. Yet it doesn't really look like an engineer or physicist came up with it, because that decimal point shouldn't really be there - it's not 10^-.6, it's 10^-6.

    So when it doubt, blame marketing.
     
  11. compuwar macrumors 601

    compuwar

    Joined:
    Oct 5, 2006
    Location:
    Northern/Central VA
    #12
    I've got one of these:

    http://www.adorama.com/LEGSNDS.html

    I've also got an ND 4.00 (13 1/3 stops) - it depends on what you're trying to do- if it's get rid of moving subjects, I recommend the 4.00.

    http://www.bhphotovideo.com/c/product/28043-REG/Kodak_1497833_4x4_100mm_96_Neutral.html
    
    It's not framed like the Lee ones though, so it's not the best in the Gelsnap holder.
     

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