I was chatting to a friend yesterday who had his Nikon D300 with a constant 2.8 aperture zoom lens (I can't remember the focal length, might have been around 17-55).

The curious thing was that he had an ND2 filter on the front of the lens - even though he was shooting indoors. The rational was that it is easier to leave the filter on at all times rather than put it on and off all the time, and he does most of his shooting outdoors.

Note: he wasn't there to take photographs. He was there to film and had his SLR with him to grab a couple of shots if he could.

Is there any advantage to keeping an ND filter on at all times? The only times I've thought of using one is to extend the shutter time, e.g. for photographing moving water.

  • 3
    I think he was just lazy. And he paid the price with using higher ISO to keep the shutter fast enough. Mar 23 '13 at 0:32

There is very little advantage of leaving the ND on when it comes to still photography. Aside from offering a small amount of protection to the lens the filter will do nothing except increase shutter times. There may be a few cases where you really want very long exposures indoors.

If you're shooting videos with your DSLR then it makes sense as your shutter speed is effectively fixed at 1/50s so you may need a ND indoors if you want to shoot at f/2.8 and there is some strong stage lighting.

If you're shooting with flash then your shutter speed may be restricted to 1/200s so again you might need the ND to shoot at f/2.8, though I've never been in a room lit up enough to be overexposed at 1/200s, nor would I want to be in that room!

I once met a photographer who left his ISO permanently set to 1600 "because noise reduction plug-ins are so good these days"...

  • Sorry, to clarify: he wasn't shooting video with the DSLR - he was using a proper video camera and had the DSLR for stills. Mar 22 '13 at 11:21
  • Well, for video the shutter speed is definitely not fixed on my 5D MK II - there is an "upper limit" which is 1s / framerate but else I can select a faster shutter if I want, right up to 1/4000s. (just checked and it works -> banding on my LCD at high shutter speed)
    – DetlevCM
    Mar 24 '13 at 12:25
  • @DetlevCM Matt said effectively, he was using the 1/2xFPS "rule" for shooting cinematic film. Going faster reduces motion blur and starts to give a stuttering effect to motion
    – camflan
    Mar 24 '13 at 13:15

There is no general advantage of having any filter on the lens all time.

Each filter serves a purpose, cares for an effect. When ever that effect is not wanted explicitey, there is no point having that filter on the lense.

Each filter comes with disadvantages and risks. When you don't need that effect, get rid of the risks.


There is almost no advantage to leaving the filter on the lens at all times as has been mentioned by several people.

If a lens hood is not used with the filter, the photos will likely be negatively affected. The filter is a flat piece of glass that usually does not have as sophisticated a coating at the front element of a camera lens. Any light falling on the surface of the filter can reduce the contrast of the photo.

Some useful information on choosing lens filters and the effects of different types can be found here:

Cambridge In Colour - Camera Lens Filters

The author of the page writes:

Filters should only be used when necessary because they can also adversely affect the image. Since they effectively introduce an additional piece of glass between your camera's sensor and the subject, they have the potential to reduce image quality. This usually comes in the form of either a slight color tint, a reduction in local or overall image contrast, or ghosting and increased lens flare caused by light inadvertently reflecting off the inside of the filter.

  • A lot of Canon lenses require a filter in order to complete their weatherproofing, so a filter is often necessary. Serious filters do have a sophisticated coating to reduce ghosting and flare, so this should not be a problem. Obviously a neutral UV filter is a better choice for protection than an ND filter, though.
    – Bobulous
    Mar 24 '13 at 16:05


I almost always had a polarising filter on some of my lenses, rather than the usual UV protective filter. I found a polarising filter really helpful in bringing out colour, removing or enhancing reflections, and of course darkening skies. Almost never took the PL off, except indoors!

Outdoors, besides extending shutter speed for moving water and clouds, it also means you can use a larger aperture in bright sunlight to avoid diffraction - you can usually avoid small apertures without an ND2 but it would help. Apart from that, it is designed to be neutral, so apart from affecting the exposure values, I don't think it adds anything (except the same protection a UV/Haze filter would)

Indoors, it seems crazy to keep it on. Apart from getting a small amount of dust or moisture on your front element, fingerprints on the lens or filter, and having to put the filter somewhere until you're back outside, I really can't think of a single reason indoors why an ND2 would be of any use whatsoever.

So in short, no real reason other than convenience/laziness really.

  • I think you mean "use smaller aperture"..."you can avoid larger apertures"? Mar 22 '13 at 11:12
  • No, with an ND filter, you reduce the amount of light, so you would be using a larger aperture than if you didn't have the filter on. In bright sunlight, rather than using f/22 and getting reduced image quality due to diffraction, you could use a larger aperture of f/11 and get better quality
    – MikeW
    Mar 22 '13 at 18:23
  • My mistake, too many negatives to process in a hurry. Mar 23 '13 at 0:39

Note that in the following I have taken "ND2" filter to mean 2 stops or 4 x light reduction. This is one way the term is used BUT more commonly ND2 is taken to mean "2 x light reduction" or 1 stop. See at end of this answer for a discussion of 3 systems of ND filter naming.

As others have noted, the required larger apertures decrease diffraction effects and allow designed motion-blurring.

However, it's worth noting that in most cases it confers either a disadvantage or a very severe disadvantage. It effectively "dumbs your lens down" with very little advantages across a wide range of conditions.

  • In low light conditions it makes the f/2.8 of your expensive lens unavailable and provides the same light as a f/5.6

  • The designed motion blurring on eg moving water leads to hard-to-avoid motion blur in lower light situations. A photo may be able to be taken hand-held at say 1/30s without filter. With filter, if only shutter speed is changed, it will require a 1/7.5s shutter speed. Happy the hand-brain owner who can hand-hold any usual lens at that speed. (With anti-shake - maybe. But such a slow speed you'd usually avoid). "

  • For a given scene, if the camera is set to the same aperture and shutter speed in both cases then the ND filter version will have 4 x higher ISO. eg 1600 ISO instead of 400. Noise happens.


ND filter naming - what does ND2 "mean":

Imre noted that I'd taken ND2 filter to mean "2 stops of light reduction" whereas, he suggests, it should mean "reduction in light level by a factor of 2". A look at Gargoyle shows that "reduction by N" rather than "N stops" is indeed by far the most common usage, although there are examples of both. There is also a 3rd method involving "density" - less common again but used by some filter makers. Examples of each of these are given below.

Reduction by N

Useful table
Wikipedia More

Both N & density :

Tiffen & Nikon examples


Useful variable ND discussion


Useful long exposure discussion

  • An ND2 filter reduces light by factor of 2, i.e. 1 stop. Your calculations seem to be using 2 stops.
    – Imre
    Mar 22 '13 at 13:27

I will speculate a little bit here as objectively there does not seem to be a good reason for leaving an ND filter on (especially indoors) - as other posters have correctly pointed out.

However, if I reverse engineer an answer, there could be situations where one would like an ND filter.

Specifically, an ND filter is used mainly to allow a longer exposure where the image would otherwise be overexposed or a wider aperture where the image would otherwise be overexposed.

Now an f2.8 lens will give a nice background bokeh effect and a slow shutter can give some interesting motion blur, especially when used with for example 2nd curtain flash. (Moving object and then slightly "frozen" by the flash at the end.)

So given a lot of speculation, it would be possible to use an ND filter indoors with flash to allows the use of a large aperture with slow shutter speeds for motion blur effects.

BUT: As others have pointed out, it is another glass interface which has the potential of negatively affecting image quality and causing lens flare. In addition, if you have to up the ISO to compensate for the ND filter, you would be losing dynamic range and introducing extra noise to your image. And finally, I would consider it very unlikely that indoors could be lit so well that the outlined scenario applies - however if you have large glass windows and it is a sunny day, it could. Artificial lighting is very weak in comparison to sunlight.

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