Some questions about ND filters.

Discussion in 'Exposure Discussion' started by Max Power, Mar 27, 2005.

  1. Max Power

    Max Power Member

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    Hi,
    One of my favourite cameras for dragging around when out and about is my Canonet. I really like to feed it Delta-400 because it is a very useful film for just about any circumstance. There is, however, a problem. When I encounter circumstances which demand 'sunny-16' I get about 1/2 to 1 stop of overexposure because the Canonet tops out at 1/500 at f16.

    I have heard that a ND filter can address this problem by giving a photographer a stop or more of flexibility. A couple of questions:

    1. Do ND filters degrade the image appreciably or are they actually pretty good?
    2. If an ND filter is labelled ND-1 or ND-2, I assume that it means that it will give you 1 or 2 stops respectively. Is this the case?
    3. Any other hints or suggestions?

    Thanks,
    Kent
     
  2. Dave Parker

    Dave Parker Inactive

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    Good quality ND filter are suspose to be 100% neutral and not affect the image at all, of course this depends on making sure it is impecably clean as to not cause any artifacts.

    The ratings of filters depends on the company making them, there are a few different ways they are rated , but in the above example, I would believe this to mean 1 and 2 stops respectivly.

    Dave
     
  3. Nick Zentena

    Nick Zentena Member

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    Hoya ND2 are 1 stop. A filter factor of 2. B&W ND filter of 1 would be 3 1/3 stops if they made one. Every 0.3 is equal to one stop of light reduction. So check what the maker means.

    The Cokins are supposed to be grey and not neutral. You'd want to avoid those.
     
  4. Bruce Osgood

    Bruce Osgood Membership Council Council

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    Nick, You sure about that?

    I believe a "Factor" of 2 would be 1.4 stops and a factor of 1 would be 1 stop. I don't know about Hoya but I have a little booklet from B+W that says their ND Filters:

    Filter
    101 2X factor = 1 Stop
    102 4X factor = 2 Stop
    103 8X factor = 3 Stop
    106 64X factor = 6 Stop
    110 1000X factor = 10 Stops

    Seems their ND Filter # hold a clue to Stops. But this is not true of their Contrast Filters where the square root of the X factor determines the Stops.
     
  5. Sanjay Sen

    Sanjay Sen Member

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    Hi Kent,

    A ND filter will not degrade the image provided that the filter is of a sufficiently good quality. I would suggest that you pay a little more and get a B+W filter. They are really good. Try to stay away from Tiffen filters - I haven't heard many good things about them. As far as B+W ND filters are concerned, they come in the following grades (as Bruce has also mentioned):

    [Designation] (Exposure Adjustment) (Filter Factor)
    ====================================
    [BW101 (ND .3)] (1 stop) 2x
    [BW102 (ND .6)] (2 stops) 4x
    [BW103 (ND .9)] (3 stops) 8x
    [BW106 (ND1.8)] (6 stops) 64x
    [BW110 (ND3.0)] (10 stops) 1000x
    [BW113 (ND4.0)] (13 stops) 10000x
    [BW120 (ND6.0)] (20 stops) 1000000x


    As you may have observed, the ND specification (.3, .6, etc.) is the log of the filter factor.

    Hope this helps.
     
  6. Nick Zentena

    Nick Zentena Member

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    Simple way to deal with filters is to divide the film speed by the factor. A factor of 1 would mean no change. UV filters have a filter factor of 1.
     
  7. Woolliscroft

    Woolliscroft Member

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    If you are using B&W film, why not also try coloured filters to darken blue sky etc? A good brand of filter, with proper anti flare coating (e.g. Hoya) should not degrade the image at all and the effects can be very interesting. My canonet GIII puts the meter light sensor under the filter, so it should compensate for the filter factor by itself (unless you use graduated filters), although it is well worth calibrating properly (the compensation factor will be printed on the packaging) as I find that mine tends to underexpose slightly with a red filter unless I bias the meter. You should need 48mm thread filters. Most won't cost much, so get the best. It is false economy to buy cheap ones, which might not be optically perfect. I keep a UV filter on mine all the time to protect the lens.

    David.
     
  8. Sanjay Sen

    Sanjay Sen Member

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    I would suggest that you buy a good filter for the largest diameter lens that you have, then use step-down (from filter to lens) rings for other lens sizes. It is a good idea to avoid step-up (from filter to lens) rings to avoid vignetting.
     
  9. Bruce Osgood

    Bruce Osgood Membership Council Council

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    You are correct.
     
  10. Woolliscroft

    Woolliscroft Member

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    Canonets are fixed lens.

    David.