Neutral Density Filters – When, How, Why
Keywords: how, to, landscape, filter, neutral, density, graduated, reversed, nd, gnd, singh, ray, lee, format, hitech, bw
ND - Neutral Density. For the beginning landscape photographer this term could just as well stand for Niggling Disorientation. The ND filter is possibly one of the more misunderstood accessories for photographers. Looking at one for the first time, whether a split-graduated type or a solid one, many may vaguely understand what its purpose is, but few instinctively know how to use it and under what circumstances. Yet, the ND is one of the two filters I consider a “must have” in my photo bag, right there next to my circular polarizer. While this article might not be for the experienced outdoor photographer, I offer this information for those who are starting out in this field and need some solid and basic information on the description, use, and purpose of this very important filter.
WHAT ARE ND FILTERS?
A neutral density filter is designed to do one thing – reduce the transmission of light to the photo sensor. Think of it as a sunglass for camera lenses. The better quality filters will filter the intensity of the light without introducing color shifts or imposing a color cast – just like good quality sunglasses do versus cheap ones. The better ones are also carefully manufactured to minimize flaring and ghosting. By reducing the amount of light hitting the camera sensor the photographer is able to make changes to exposure values. This is done to achieve certain effects - such as to take advantage of reduced depth of field, by allowing wider aperture settings, or to photograph subjects in such a way as to project movement or fluidity through longer exposure times. A variation on the solid ND filter is the graduated ND filter, or ND grads. These serve a unique purpose and so are a little more specialized. They allow you to capture the full dynamic range of an outdoor scene within one single exposure. Since they have a clear section and an opposing filtered (darkened) section, they can compress the exposure values of the light areas and dark areas present so that the camera can record both highlights and shadows with a reasonable amount of image detail. A bright sky against a darker foreground is a good example. Neutral density filters come in several forms and configurations. I’ll group them into three basic types.
The Solid ND
These filters come in two shapes, the more common circular, screw-on type (just like your polarizer), and the slide-in square/rectangular shape. Both accomplish the same thing; they are just designed to attach to the front of your lens differently. Is one better than the other? The end result is the same, but as I’ll point out later, I believe each is better suited based on one’s shooting preferences and budget.
The solid ND also comes in varying strengths. The strength of an ND is typically measured in f-stops. The strength of these filters usually range from 1 to 15 f-stops of filtration.
The Variable ND
This filter is only made in the circular design and screws on to the front of your lens. It has a rotating bezel much like a circular polarizer. As the name implies, these ND’s are designed to give you a varying range of density from about 2 to 8 f-stops of filtration in one package. A great concept, especially if you have limited space in which to carry your gear. While very popular, they do have some limitations, and they also tend to be more expensive. These are not your usual ND filters – they do not use density dyes to darken the filter material. They use opposing polarizing filters, that when rotated on the same axis increase or decrease the light stopping capacity of the filter.
The Graduated (or Split) ND
The graduated ND filter also comes in both circular screw-on and rectangular types. I’m going to stop here and make a rare, absolute statement. Circular screw-on graduated neutral density filters are absolute rubbish. Do not buy one. If you own one, sell it to your worst enemy. Get that pointless thing, designed by evil elves from somewhere south of the North Pole, out of your bag once and for all. Okay, I feel much better. ND grads, as they are sometimes called, also come in varying strengths - from 1 to 5 f-stops. Some makers even offer what is called a reverse ND grad. This unique filter is used when shooting into the sun at sunrise/sunset. The filter has the usual density transition except that it is darker at the center and then fades slightly toward the top. This will give you more filtration where the sun is hanging over the horizon without making the upper sky too dark.
Originally written on October 13, 2015
Last updated on December 7, 2017
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John D. Roach (jdroach) on December 8, 2017
Fine article. Variable ND and the regular .3, .6, .9 ND are what Keep with me. Sometimes size of kit limits to the VND. You make good points, Ernesto.
Annie Parm (annie459) on August 7, 2017
Everything was awesome.Thank you.
Edwin Wilson (hattrick) on May 28, 2016
I should add to my comment above, that I use a 2 stop soft Singh-Ray ND Grad. filter in a Cokin P series filter holder. I shoot with the Nikon D7100. Skip
Edwin Wilson (hattrick) on May 28, 2016
Thank you for your nice article. Could you please tell me about the proper metering through a graduated neutral density filter (ND Grad). You mention using the Matrix metering and in manual mode, metering at 0. John Shaw in his classic book, Nature Photography Field Guide, talks about first metering the bright area, eg snowy mountain top, through the darker part of the ND Grad, to allow for any tonality discrepancies of the filter, adding compensation eg +2 for the snow, and then adjusting the position of the filter and shooting. I assume he is using spot metering instead of Matrix. Will Matrix metering and using 0 on the metering analog truly give an accurate reading for the whole scene using the ND Grad? Shaw in that book, may have been talking only about film rather than digital then but I am not sure. Also, how does one blend 2 photos in Photoshop Elements 11 if one were to just take 2 different exposures without the filter one for the snow and one for the darker foreground? Is special HDR software needed? Thanks Skip
Steve McTeer (NRVVA) on February 13, 2016
Excellent introduction, for me, to the application of ND filters. Thanks!
Gary Worrall (glxman) on February 6, 2016
Much appreciated Ernesto, This has been on my "to do" list for some time, I have a 14-24 and would love to get the Lee Filter Holder and a Big Stopper, Trouble is I keep buying other things instead! This year maybe , I hope Thank you for taking the time for this detailed article Regards. Gary
Craig Menzies (foamfollower) on December 1, 2015
Thanks for this article,it's clarified a lot of questions for me about using ND Filters and the importance of this still despite software options in the Digital World.
Mark Yeazel (Mplsmark1) on November 4, 2015
An excellent article. It should help me progress quickly beyond experimentation stage. Thanks!
donald cvitkovich (dcvitko1) on November 2, 2015
Appreciate clear concise coverage. Good article
Joanna Pecha (PixiePixels01) on October 19, 2015
Thanks for a great tutorial..Look forward to implementing!
User on October 17, 2015
Excellent article. It brought back some of the basics that I never should have forgotten.
Gary Marshall (gtm) on October 17, 2015
Good refresher for me. Having just added the Lee 100 ND filter kit to my bag and having the ability to rotate the ND grad on the ring makes it nice. Thanks for writing about this. As a thought how about doing one on circular polarisers especially when using wide angle lens. I tend to get that dreaded dark blue vignette effect in the upper right of my sky.
Ernesto Santos (esantos) on October 17, 2015
John, For ND filters look at: B+W, Singh-Ray, LEE, Tiffen, Hoya. For Grad ND's look at: Hitech, Singh-Ray, LEE. These are listed in no particular order.
John Hernlund (Tokyo_John) on October 16, 2015
Do you have any recommendations for good filters that are widely available? I was excited to play with ND filters a while back and bought a Kenko PRO-ND1000, which is a 10 stop ND filter (Kenko is Tokina in Japan)...unfortunately the quality is terrible, colors and contrast are terribly muted and the resulting image looks nothing like the same image taken without the filter at 10 stops faster exposure. I tried to come up with a correction scheme in Photoshop, but failed to produce anything reasonable.
Marsha Edmunds (meadowlark2) on October 16, 2015
This was so useful. I learned some things here that I had never thought of or known before. Can't wait to experiment.
Ernesto Santos (esantos) on October 15, 2015
Duke, That has not been the case in my experience and I cannot think of any reasons optically why that would be the case. Neutral Density filters simply hold back the light and nothing more. Now, there is a combination filter made by Singh-Ray that combines a a variable ND with a polarizer and a color intensifier called the Vari-N-Trio, but that is something different, adding color intensification purposely. Lower quality ND's will impact the image quality but in a negative way, such as loss of contrast and color shifting/color casts.
User on October 15, 2015
I'm told that an ND filter, solid, when used to extend a typical exposure, will enhance the overall color. True or false?
Ernesto Santos (esantos) on October 15, 2015
Geoff, Thanks for spending time to read and comment, much appreciated. My point about screw-on filters was related to graduated neutral density filters only because the transition of those filters forces you to make compositions where the horizon runs right through the middle of the frame, generally not the best of framing options. There is nothing wrong with solid or variable density filters that screw on to the lens. I have several and use them frequently. Hope this clarifies. :-)
Geoff Baylis (GBaylis) on October 15, 2015
Great article Ernesto. You made the point that screw-in variable grad filters are to be avoided, but exactly why is that? (I should point out that I don't own one!). Is it because once secured onto the lens you can't rotate it, like you can on a polarising filter? If it could be rotated, would that put them on a par with rectangular drop-in filters, and if not, please elaborate on why that's not the case. Thanks, Geoff
David Summers (dm1dave) on October 13, 2015
Great info! Thanks for sharing.
Ernesto Santos (esantos) on October 13, 2015
Hi Doug, Thanks for your great feedback. Yes, you are correct, and do mention this (if in somewhat of a fleeting way) you can in most cases correct the exposure range in post processing. If the images to be blended are taken with care to not move the camera you can get very good results. The difference is in an intangible sense that getting a single correct exposure in-camera using ND grad filters is somehow different. Better? No, not necessarily. To my eye they just seem a little more natural looking. One is not better than the other and I consistently use both methods. I think it is good to have the knowledge and skills to employ different techniques to achieve the same end. That makes us better photographers.
Doug Nickle (fivesense) on October 13, 2015
Thank you Ernesto! Great article with lots of good information. Question- how are ND filters different than what one can achieve in post processing, i.e. using the graduated filter tool? Are ND filters simply better at achieving the best exposure in-camera? I always prefer getting as much as possible in-camera...
User on October 13, 2015
Excellent article Ernesto! You've covered all the bases.