grey filter

Discussion in 'Beyond the Basics' started by mentos_007, Mar 20, 2005.

  1. mentos_007

    mentos_007 The Freshmaker!

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    hey! I need your help. I'm going to buy a grey filter to my s5000 and it's NDx4 filter. It lets "smaller" my apperture for 4 stages... what does it mean? :) my s5000's lowest apperture is f8 so if I use the filter I'd be able to have something like... f12 ?? am I right?
     
  2. mad_malteaser

    mad_malteaser TPF Noob!

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    I didn't even know you could buy filters for the s5000. If you get it, let me know how it goes!
     
  3. mentos_007

    mentos_007 The Freshmaker!

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    yes you can because with a cam you were given this plastic adapter that reduces the diameter to 55 mm.
     
  4. Dweller

    Dweller Inconspicuous Supporter

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    Someone may come along with a better explanation but I will try :)

    A Neutral Density filter blocks stops of light. If you composed a shot at f/22 (4 stops down from f/8) then put this filter on you would need to open the lens up 4 stops to compensate. I believe that ND filters are used a lot to slow down the shutter speed. For example if the same shot you were composing gave you a shutter speed of 1/500 but you needed a slower shutter speed to imply motion in the shot then you could put on the ND filter and lower the shutter speed 4 stops to 1/30

    I hope I have not confused the matter too much hehe
     
  5. Canon Fan

    Canon Fan TPF Noob!

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    Usually cameras are limited by their "widest possible" aperature like say f/1.2 so to be limited only to f/8 (instead of a smallest possible of say f/22) is a bit wierd.

    Anyway an ND or grey filter is normally used to focre certain camera settings you wish to use when there is too much light to allow for them. Lets say a certain shot of a strem would call for 1/250 shutter at f/8 with ISO 100 film. But this high shutter speed would completely freeze the motion of the water and you want it blurred. You could then you a 4x ND filter that would reduce the light so that a setting of 1/30 at f/8 with ISO 100 giving you a nice blurred effect in the water.

    Another example would be that this could also allow you to better control depth of field while using a specific shutter speed. Lets say that you are shooting a sporting event with a distracting background (so you want it blurred) but the lighting would force you to use a setting such as 1/250 sec at f/8 with ISO 100. The shutter speed would be high enough to freeze the action but f/8 would leave the background fairly in focus. You could then use a 4x ND filter to limit the light and allow you to use 1/250 sec at f/1.8 and ISO 100 which would nicely blur the background but still freeze the action and give a proper exposure.

    My math may be off on the conversions but it should help to give an idea of what the filters are used for :wink:

    Oops I see Dweller was working on a reply while I was busy typing mine :oops:
     
  6. ferny

    ferny TPF Noob!

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    Yup, ND filters reduce the amount of light entering the lens. They're grey so that there is no colour cast to the image. The idea of them is, as you said, to allow you to use longer shutter speeds but they also allow you to use fast film in bright lights and allow you to open up the aperture when you wouldn't be able to normally. So if you're half way through a roll or need to take just one shot in a very bright place you can slip on your ND filter, take your shot, take the filter off and continue as you were.

    I left my reply window open too long as well. :oops:
     
  7. mentos_007

    mentos_007 The Freshmaker!

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    yeah but how do you know that f22 is 4 stops down from f8 Dweller????
     
  8. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    wide open/more light
    f/1
    f/1.4
    f/2
    f/2.8
    f/4
    f/5.6
    f/8
    f/11
    f/16
    f/22
    f/32
    f/45
    f/64 and so on...
    closed down/less light

    That's the standard aperture scale in 1 stop increments.

    You can also control exposure with shutter speed.
     
  9. Dweller

    Dweller Inconspicuous Supporter

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    Well, I was going to say I cheated by looking at one of my lenses but then I just noticed I mis-counted hehe

    sorry about that.

    ksmattfish has posted the correct aperatures for each stop :)
     
  10. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Does the "x4" mean 4 stops, or that it will require 4 times the exposure? Each stop is a doubling of the exposure, so to get 4 times the exposure would mean increasing the exposure by only 2 stops (2 x 2 = 4).
     
  11. mentos_007

    mentos_007 The Freshmaker!

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    That's what I neede!! thanks!!! no NDx4 means "4 stops down" so to f22 :)
     
  12. photobug

    photobug TPF Noob!

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    I think most ND filters are rated 2x, 4x or 8x, which is 1, 2 or 3 stops.
     

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