ND filters vs polarizer's

Discussion in 'Accessories' started by kylebybee, Mar 16, 2016.

  1. When shooting on bright days and your camera doesn't go to 1/8000 of a second, the option is using a ND filter, preferably non circular.
    Has anyone played around with a non circular polarizer for the same reason and did work and give different look? Or is a non Circular
    polarizer ensentially the same as an ND filter
     
  2. No a polarizer is not the same as an ND filter. The polarizer has a fixed density like an ND, but it has the "polarizer" effect that darkens the sky at certain angles, removes reflections off water and glass at some angles, and messes up LCD displays.
    An ND has none of those additional effects.
    One side effect is that a non-circular polarizer will mess up your auto focus. that's why CPs are popular on DSLRs.
     
  3. Thank you Charles!
     
  4. Sometimes, when I haven't had an ND filter with me, I've used a circular polarizer as an ND. I accepted the effect of removing reflections, and turned the polarizer to a position that had the least interaction with the sky. It's not the same but, especially when traveling, I used what I had available.
     
  5. david_henderson

    david_henderson www.photography001.com

    Its a bright day here. To require a shutter speed of 1/8000 requires me to use ISO 3200 with my f4 lens wide open. Personally its unlikely that I'd want or need to do all that in combination. Have you considered the possiblilty of achieving whatyou need by adjusting the camera rather than via a filter.
    The "ND " component of a circular polariser today is only about 1.5 stops.
     
  6. To further on what Charles said - it's not even so much that a Polariser has additional features - it simply does something else. A polariser filter filters polarised light, which leads to the effects that Charles described. The "standard" use to make the sky more blue is nice, but it's cutting glare, reflections and highlights that make CPs extremely useful tools - an effect you cannot replicate in post processing, so it's one of the few filters still useful with digital. Note that it is a sort of "selective" filtering - some areas of your photo will be affected, some not so much, depending on the angle towards the light source, and the effect can become very uneven on wide angles.
    A perfect ND filter filters all light for the given amount of stops - it's not selective, but an uniform effect, essentially slowing down your shutter speeds (or wider apertures). Ideally it is a pure grey, though cheaper ND filters may have a colour cast. ND filters can possibly cut a lot more light than a CP, some go up to 10 stops less light.
    There are no circular ND filters, but graduated ND filters to exist - to 'underexpose' only a part of the photo. With digital their use is limited, as the same effect is done a lot easier and more precise with blending two exposures in post production. But ND filters (esp. more heavy-handed ones, approx. 3 stops or more) can be useful with digital, as they enable you to shoot either speeds or apertures that otherwise would not have been possible. Most people use them for long exposures, though, rather than wide(r) apertures.
    But as David said, in bright sunlight, with 1/8000th available, there is not much use yet for filtering. Following Sunny 16 (which does apply where I live), it means 1/6400th with f/2 at ISO100. So considering 'normal' fast primes, you only miss out on f/1.4, and 1 stop difference would be easy to "solve" in post processing.
     
  7. Yes, occasionally I do use a polarizer as a ND filter--because I don't have any ND filters and it reduces the light by 1-2 stops but, as others point out, polarizers have additional effects that ND filters don't have.
     
  8. A polarizer will cut down the amount of light coming through the lens by a couple of stops when turned to its full-effect position. But it is not neutral like an ND filter since it affects the colors (depending on angle, etc.)

    I've been shooting for 40 years and never had need for 1/8000. In fact, in film days the fastest shutter speed I had was 1/2000 on my Nikon F2 and I'm not sure I recall using that. With digital, as Wouter says, you can go a long way in dropping your ISO before you get to 1/8000 or the need for an ND. Or, depending on what you're shooting, move out of the bright sun, use a scrim, etc.
     
  9. If you're trying to shoot a cropped f/1.4 50mm as a people lens in daylight and trying for paper-thin DoF then the lack of a 1/8000s shutter can be felt. Even then though, I'm not sure a polarizer would have cut the sun enough to hit maximum aperture.
     
  10. William Michael

    William Michael Moderator Staff Member

    On the tangent topic of ‘when/why do we ever need and ND filter in bright sunlight?’
    Occasionally, especially for portraiture at the beach or in snow, the EV, especially of the background scene can be EV = 16~17 (one or two stops brighter than the F/16 Rule). Such a bright scene requires typical Camera exposure parameters: F/16 @ 1/200s ~1/400s @ ISO 100, to not blow parts of the scene, especially when using a Digital Camera.
    Now: F/16 @ 1/200s ~1/400s @ ISO 100 ≡ F/2.8 @ 1/6400s ~ 1/12800s @ ISO100
    Considering that often, especially for Weddings and Portraiture, an F/2.8 or faster lens is chosen for Shallow Depth of Field and also considering the lowest ISO of many Digital Cameras is ISO100 and also some Digital Cameras only have 1/4000s as the fastest Shutter speed, then on these special and rare occasions an ND filter is required to make this type of shot.
    There is reasonably common usage of an ND Filter for this exact purpose in the beach/seaside areas close to where I live and where there is a passion for “Beach Weddings” and or the B&G want a stop-off at the beach for Bridal Portraiture on their way t the Wedding Breakfast. Also the beach is a scene for Portraiture, generally.
    I have found an ND Filter (ND8 - three stops) is the best to use for the purposes of Shallow DoF in these shooting scenarios with my camera gear; rather than using a CPL or PL.
    WW
     
  11. I use an ND in bright sun to be able to slow down my shutter speed without getting into diffraction land on the diaphragm. My typical use is for moving water. Even though it's fairly trite, I like the effect of a slow shutter speed on waterfalls etc.
    I have a CP and use it when shooting scenery to increase the contrast between clouds and sky. Here in So. Oregon we have lots of blue sky with fluffy cumulus clouds that look nice above the scenery.
     
  12. You will lose about 2 stops of light with a PL filter. Sometimes I stack an ND on top of a PL filter to further decrease the light coming in.
     
  13. I like using a 10 stop Lee filter in bright afternoon light when there are lots of cumulous clouds flowing by, especially at the beach. The long exposures seem to intensify and give a little more dimensionality to the image. I see that Lee has added a 15 stop to their collection recently. I will try stacking my 6 stop and 10 stop together soon and see how that works out.
     
  14. Or is a non Circular polarizer ensentially the same as an ND filter​
    No, they are not, though any polarizer will cut down the light hitting the sensor...
    "Circular" in reference to polarizing filters has nothing to do with the physical shape of the filter, but with the way the light that goes through it comes out. A circular polarizer, or a linear polarizer can be square or round, it's all in how it's made inside that determines whether it is a circular or linear polarizer.
    I won't try to explain it all,but here are a couple Wikipedia articles:
    Polarization (subhead: circular polarizers)
    Circular Polarization
     

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