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Thread: asking about filter to reduce light

  1. #1
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    asking about filter to reduce light

    Hi experts,I am using lens 50 1.4 on full frame . Sometime I open max aperture at 1.4 to have some nice effect on bokek . fastest speed 1/8000 , iso at lowest ( 50 ) but light still over than standard .What should I do to reduce the light a little bit ?Or should I attach the ND filter to reduce few stops ? In this case , will it be impact on bokeh shape ? Please advise .Thanks all.

  2. #2
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    For reducing outdoor ambient light an ND filter would be the only choice other than wait for an overcast day or a different time of day obviously.

    I do not believe the bokeh would change in any way with an ND filter assuming you would use the same f-stop.

    Singh-Ray and Tiffen both make very nice variable ND filters that cover a wide range of ND values in one filter.

  3. #3
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    ND filter is essentially a set of color-neutral (ha! at least that's the hope) sunglasses for your camera. It's not in any way refractive, at least to any relevant degree, so it's not going to change the bokeh qualities by using it. I've heard reports that variable ND filters tend to also be variable in color shifts, but admittedly have never bought and/or used one.

    I chose to get a 3-stop and a 6-stop in 72mm and 77mm filter sizes (originally in 77mm, but got tired of using step-down rings, having them get stuck to my filters, and being unable to use hoods or get to the filters in those cases. (A CPL on top can buy me perhaps two more stops, I could stack them for 9-stop, etc.) I use my ND filters a lot more often for using studio lighting outdoors, so I can keep shutter speeds at/below sync speed while achieving a thin DoF. As I explore more with fast primes, I'm amazed at how often I need that 6-stop ND.
    We're a Canon/Profoto family: five cameras, sixteen lenses, fifteen Profoto lights, too many modifiers.

  4. #4
    Senior Member neuroanatomist's Avatar
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    Personally, I find that a 3-stop ND is ideal for shooting a fast prime wide open on a bright day (e.g. with my 85/1.2L II). No effect on bokeh, no effect on sharpness provided you use a good quality filter (I use B+W). If you find that you only need 1-2 stops of reduction, there will be no meaningful impact on IQ going from ISO 100 to ISO 200 or 400 with the ND filter on the lens. I'm not a fan of the variable ND solutions, usually there's a sharpness hit and if you try to use them on wider lenses you get a 'Maltese cross' artifact due to the polarization (a vari-ND is essentailly a CPL stacked on a linear pol filter).

    ISO 50 doesn't really buy you anything, it's just ISO 100 digitally pulled a stop by the camera. Well, if you're using an auto exposure mode (P, Av, Tv) it will allow the camera-selected value compensate that extra stop, but you can acheive the same thing with a manual exposure setting at ISO 100. If a highlight would be blown at ISO 100 with a given aperture/shutter combo, it'll be just as blown at ISO 50.

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