I had a question on my Facebook page today about Variable ND (Neutral Density) filters and my answer turned into a full on guide to selecting and understanding ND filters which deserved it’s own blog post. So thanks to Michele for suggesting the topic and I hope I answer your question 🙂 History Back in the days of film photography a professional photographer would have had a wide variety of filters in their camera bags but these days Photoshop has replaced nearly all of them, thankfully! Pretty much the only filters a professional photographer will carry these days are a Polarising filter and a set of ND filters. I won’t go into Polarising filters here except to add that with the popularity of ultra wide angle lenses and images stitching they are becoming less and less used. The Options The effect of using ND filter is to increase or equalise the exposure time for an image by darkening all or part of the camera’s view, it’s a bit like having sunnies for your camera 🙂 ND filters are generally used to either lengthen shutter speed to smooth out motion or reducing the dynamic of a scene by darkening part of the view. Another use of these filters is to allow you to decrease depth of field in very bright situations. A word of warning when purchasing your ND filters, to work effectively an ND filter must be a true neutral gray otherwise a colour cast will be introduced so avoid cheaper filters. For example I have read that the ND filters in the Cokin filter system are not at all neutral an introduce a pinkish colour cast 😦 There are two options for mounting ND filters to your lens:
- Buy 1 or more glass filters to screw onto the end of your lens
- Buy a filter system and a collection of ND filters to slot into it
Additional there are 4 types of ND filters available:
- Solid ND filter
- Hard graduated ND filter
- Soft graduated ND filter
- Variable ND filter
Finally, ND filters come in a variety of strengths, indicating how much light they block out. Unfortunately filter manufacturers have several different ways of measuring the light reduction values which can be very confusing, check out this wikipedia page and scroll down to “ND filter types” for a comprehensive table of light reduction values. Graduated ND Filters Graduated ND filters are used where there is a large dynamic range between the brightest parts of a scene and the darkest part of a scene. For example a sunset or a scene taken towards the sun where the sky is very bright compared to the land. Without a graduated ND filter you would have to select either the sky or the land to be properly exposed and sacrifice the other to be blown out (pure white) or under exposed (black). So a graduated ND filter will allow to get a much better sunset shot in a single frame, the alternative being to take multiple exposures and blend them together afterwards in Photoshop or Lightroom. Graduated ND filters come in 2 types, soft & hard, the difference between them is the transition from the clear part of the filter to the gray part. As the names imply soft grad’s fade smoothly from clear to gray whilst hard grad’s transition abruptly along a hard line. Soft grads are much more popular and a lot easier to use as they are more forgiving whilst hard grads are really only suitable in certain scenarios such as oceanic scenes where you can align the transition line along the horizon. It is important to be aware that ND graduated filters are a compromise, very rarely will the transition occur exactly where you need it, so you will get trees that are darker on the top than the bottom or sand dunes with a similar problem. Horizons are rarely flat in well composed images and nature has a way of doing things outside our plans, as always it’s about finding the right tool for the job at hand 🙂 Solid ND Filters Solid ND Filters serve a different purpose to graduated as they affect the whole image. Typical uses for a solid ND filter would be when taking waterfall scenes when you want to smooth out the flow of water and can afford a longer exposure time or when you are shooting on a very bright & evenly lit day and want to decrease your depth of field by opening up the lens. Variable ND Filters Finally we have variable ND filters. These tend to be more expensive and are usually created by having 2 specially designed circular polarising filters placed next to each other with one of them fixed and the other rotating. Simply rotating the outer filter ring will change the effecting light reduction of the filter within a set range. The benefits of Variable ND Filters are:
- Flexibilty, you only need 1 filter for a variety of scenarios
- No need to keep changing filters (which is a pain with screw-on filters)
- Easy to experiment with different settings
The drawbacks to the Variable ND filter approach are as follows:
- Very limited brand options with conflicting reports on image & build quality
- Expensive if you mostly need a limited range of light reduction
- Expensive if they don’t provide the image quality you are looking for
- You cannot get graduated Variable ND Filters
- Only come as screw-on filters (that I know of) so see below for the pros and cons of screw-on vs filter systems
Filter Systems By far the most cost effective and flexible way to purchase any type of filter is to buy a filter system which consists of a filter holder, an adapter ring for each of your lenses and a set of filters. The benefits of using a filter system over screw-on filters are:
- You only need to buy one of each filter
- Filters can be rotated and slid up and down to allow for ideal positioning
- Lens vignetting can be avoided with the right system for your lens collection
- Filters can be quickly & easily installed and removed
- Easier to attach multiple filters
The negatives of a filter system over screw-on filters are:
- Higher start up costs as you need to buy the holder and attachment rings just to get one filter
- There are some low quality systems out there which should never be put in front of decent lenses!
- Variable ND filters are not available in this format
If you do go down this path then it is important to make sure you get a good quality filter system as all you future filters will come from a single manufacturer and what’s the point buying quality camera equipment and putting a piece of cheap plastic in front of it! Personally I would recommend the Lee Filter System which is used by most professional photographers and they provide the highest quality products. Screw-On Filters The simplest way to get filters in front of your lenses is to buy a circular screw-on filter. There are many filter companies out there that sell single screw-on ND filter of varying quality, basically you get what you pay for so don’t skimp. The benefits of screw-on filters over filter systems are:
- Low start up cost
- Less bulky
- Plenty of options
The negatives of screw-on filters over filter systems are:
- Wide angle lenses can produce lens vignetting as the filter edges are so close to the lens, especially if multiple filters are stacked
- Need to purchase a new filter for each diameter lens in your collection
- Bulky to carry around large filter collections
- Graduated ND filters are not available as screw-on filters
- Much harder to attach & detach filters
Michale’s Answer As far as Variable ND Filters go (to answer the original question from Michele) no I have never used one and in my opinion they have limited use and would have to be proved to produce a quality result with professional build quality before I would consider buying one myself. That doesn’t mean they don’t have a place for certain photographers but as a screw-on only solution that wouldn’t integrate with a filter system they would not work well if you also needed to use Graduated ND filters. As far as I can tell the Singh-Ray Vari-ND Filter is one of the best around but I’ve also read some bad reviews on it and at #350+ USD (depending on filter diameter) it’s not cheap. They are also quite thick so the chance of vignetting is increased over standard screw-on filters, in fact Singh-Ray themselves have a disclaimer about vignetting on their Vari-ND product page lol. Also, I gather some portrait photographers are using Variable ND filters to achieve certain unique lighting effects, so intended use always plays a part in such a decision as well. If anyone has any good / bad experiences with Variable ND filters then I would love to hear them 🙂 Summary So to sum, up ND filters are one of only two types of filters you still need in your camera bag but that doesn’t make choosing the right filter easy. Personally my approach to filters is to avoid using them whenever possible to enable me to produce the highest quality image possible from any scenario. I will always opt for multiple exposures of a scene over a filtered version, sure it takes a bit longer to blend the images to get a finished result but I’m much happier with the quality I end with. On the other hand there are always situations where an ND filter is the only way to achieve the desired result. I currently own 2 x ND screw-on filters which I rarely use, if I ever found myself using them more frequently then I would without doubt purchase a Lee Filter System with a set of ND filters and ND Soft Graduated filters. Of course whenever I approach a waterfall the ND filters come out of the mothballs to produce the ol’ clichéd “Smooth Flowing Water” look :wink:. Note: All of the images shown in this post were taken without the use of any kind of ND filter using HDR techniques to show the full dynamic range of the scenes. These images are all for sale on my web site, simply click on any image to get more information.
Great article but a slight correction for you. There is another option to those not wanting a screw in variable nd filter. Light craft workshops makes a drop in matte box variable nd filter option that I’ve heard is excellent. With excellence almost always comes a big price tag and those are no exception. Really just made for video though.
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Thanks for the info Shane 🙂
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Dave,
Just passing by a few pages on GND filters and I have to say I found your post to be very clear and pedagogical including a lot of interesting thoughts and experience, thank you!
Just one thing I thought to add, and that is regarding the disadvantages of screw-on filters where you mention the cost of purchasing new filters for each diameter lens in your collection.
I agree, however one can (at least potentially) avoid this particular disadvantage by buying a single set of filters to fit your largest diameter lens together with one or more much cheaper step-up rings. The risk being possible vignetting at wide angles due to the overall thickness of filter and ring(s). I recently bought as good as I could afford 77mm CPL and VND filters along with a Kood 72-77mm step-up ring (costing only an additional 7GBP). This then covers both my 10-22mm and 18-200mm EF-S lenses. Job done. I haven’t tested it yet for possible vignetting at the wide end however. Maybe only 12 or 13mm will be possible for example.
Thanks again and will enjoy reading your other posts I’m sure!
Regards,
Adrian
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Hi Adrian, thanks for your comments 🙂
You make a very good point about step-up rings which indeed can help keep the cost of purchasing screw-on filters down, just make sure you start with the largest diameter lens you are likely to purchase in the near future.
77mm is certainly a good size to start with as you should be covered for most wide angle lenses.
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One very important caveat about adapter/step up rings. Watch out for galling! When two pieces of the same metal are joined or threaded together , they tend to bind. And because most filters and adapters are aluminum, and are very thin, they can be a disaster to remove, That is why almost all of my filters are by B&W – they’re not aluminum. Brass, bronze, steel, it matters not so long as they are different. And for all you Tarzans out there – finger tight is enough. Nuff said.
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Thanks for the information Thomas, very useful 🙂
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You can be so much more creative with a Solid ND filter – the Magic Cloth Technique.
Great article and such a comprehensive guide.
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Hi Tony, thank for your comments.
Just checked out your web site, stunning images, makes me wish I lived nearer to Iceland 🙂
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Great post! I have a Cokin filter system and a few screwable high quality filters. I’m thinking about replacing my Cokin System (I’m not happy with the color cast and lens flare) with a Lee Filters System (but the high price tag dissuades me) or buying a few additional screwable filters.
When I was reading your post I said to myself “wow, his pictures are great. I’m going to use the same set-up as this guy” (as I was really a bit lost in my search for the best solution). At the end of the post you say there are no nd filters used in the photos of this post and I thought “this is amazing. Let’s forget about ND grads.” (I also really like HDR and do quite a lot of work in HDR too, but I nevertheless use some filters.)
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Hi Steve thanks for dropping by, you’ve got some great shots on your Flickr page 🙂
I must admit I like to keep a simple & spontaneous approach to my photography and having to attach and remove filters is a bit of a pain, I’d much rather just grab my camera and start shooting what nature puts in front of me.
I believe ND grads are always a compromise and I’d much rather spend the time in Lightroom & Photoshop getting my images just the way I like them (my wife tells me I’m a bit of a perfectionist lol).
I also believe it’s important to have your own style and to keep evolving it which means avoiding using the same formula for every photo you take. These days there are many landscape photographers out there and it seems they all have a gallery of stunning long exposure seascapes, rivers & waterfalls, not that there’s anything wrong with that but there are plenty of other approaches to taking photos with moving water.
Never be afraid to experiment and have fun.,Photography, after all, is an artistic expression 🙂
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I was reading your article and remembered something I had seen on the Schneider web page. This is taken from your article on variable nd filter drawbacks: “Only come as screw-on filters (that I know of) so see below for the pros and cons of screw-on vs filter systems”.
There are variable nd filters for the lee system from schneider: https://www.schneideroptics.com/ecommerce/CatalogItemDetail.aspx?CID=466&IID=8088
It’s called the true-match nd kit. Comes for 4×4″ and 95mm.
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Thanks for your comments Hans, this is obviously another option for use of ND filters though it would appear from watching their video that (due to the use of dual polarizing filters) this setup cannot be used with wide angle lenses.
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Dear Dave,
Thank you for an insightful article. I am an amateur photographer enamoured by the effects of an ND filter whether it be waterfalls, the sea or streets during the day!
I was suggested to buy a non variable ND filter and was recommended B+W 72mm ND 3.0-1,000X with Single Coating (110). Is this a variable or non variable ND filter? Look forward to your response before I invest in the same.
Regards,
Chetan.
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Hi Chetan, thanks for stopping by 🙂
I have no personal experience with the B+W 72mm ND 3.0-1,000X filters you have mentioned but I gather that it is an ND 3 non-variable filter with an f-stop reduction of 10 stops and no multi coating.
If you’re looking for some more info regarding this filter checkout this Flicker thread which seems to have some useful opinions by people that have bought one.
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I don’t see a link to the Flickr thread that you mention in your above reply. Can u repost a link? In regards to the BW 3.0 – 1000X filter. Thanks!
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Hi Kim, here’s the link to the Flickr thread http://www.flickr.com/groups/longexposure/discuss/72157603906990606/.
Happy New Year 🙂
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Hello Dave,
My name is Travis and I am
Wondering if you think I could achieve
Some great photos using a 58mm Inca
ND filter just learning at the moment
Trying to improve my skills I would really
Appciate some feedback if you can Travis)
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Hi Travis,
I’ve never used Inca filters but I gather they are mid range as far as quality goes and don’t appear to have a coating which won’t help.
One thing to be cautious of with low to mid range filters is that they can degrade image quality and possibly cause a colour cast on your images.
I would recommend searching for some comments about them on Google first.
As with most things you buy in life, you get what you pay for so if you’re going to put something in front of your lens then make sure it is the best quality you can afford 🙂
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Dave, thanks for the article. under the options you state- “ND filters are generally used to either increase shutter speed to smooth out motion or” don’t you mean decrease the shutter speed not increase it? Thanks, Mark from Freehold, NJ
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Thanks for stopping by Mark 🙂
Fair comment, you could read it either way. By “increase shutter speed” I mean increase the time the shutter is open by using a longer shutter speed not making the shutter speed faster which has the opposite effect.
What I should have said (and have now changed it to) is “lengthen shutter speed” which hopefully makes it clearer, thanks for pointing that out 🙂
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Graduated ND filters are not available as screw-on filters????? NONSENSE! Tiffen makes them
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Valid point Jan, I’m not sure if they were around when I researched this post back in 2012 but they certainly are available now.
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Thanks, Dave, for a very thorough & comprehensive discussion of the various ND filters. When I looked into these filters a few months ago, I couldn’t even get a sensible description of the difference between hard & soft ND grads direct from the manufacturers, which rather startled me. And I see lately there’s a “reverse screw in ND grad”, which enables you to point straight at a setting sun & lower the level of light in the area of the sun, to bring up the colours of the rest of the scene – a bit specialised, for most of us, I think.
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Thanks for your comments Pete.
I hadn’t heard of reverse ND filters before, sounds like it would be tricky to get the exposure just right as the light changes so fast with the setting / rising sun.
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Hi Dave, thanks for a clear summary about the ND filters. It’s a lot to consider when trying to decide on which filters to purchase! After reading your article, I think I might hold off on buying ND filters for now. I am however still looking at getting a polarising filter though. From what I have read, it is not possible to remove glares from a scene using lightroom or photoshop, hence polarising filter is the only way to solve this. Is that true from your experience? Also, do you have any polarising filter that you recommend or steer clear from? Thanks
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Hi Lee, I’m glad you found the article useful 🙂
What you are saying about polarising filters is partially correct, while you can reduce the glare and haze to some degree in post processing it will never achieve the effect that using a polarising filter would give you. If it is the effect that a polarising filter has on the sky and clouds then that can be achieved more successfully with post processing.
However there is one simple solution that eliminates the need for a polarising filter, shoot with your back to the sun so there is no light bouncing off the water into your lens. Not always possible I know but often just positioning yourself appropriately can make all the difference and eliminate the problem with how a polarising filter gives uneven blue sky on wide angle lenses.
Having said that, under the right circumstances there’s nothing wrong with using a good quality polarising filter. I am not familiar with which brands are best but I would look at getting one aimed at professional use, it’s definitely a scenario where you get what you pay for. The important things to look for are the quality of the glass, the coating on the filter and the quality of manufacturing. I know Singh-Ray filters are very good (and expensive) also Tiffen, Hoya & B&W all do good filters just steer clear of their low end ones and cheaper brands like Cokin if you can.
I have recently written an article on my new blog with some tips for getting long exposures without using ND filters which you may be interested in
http://madaboutwa.com.au/noble-falls-waterfall-walk-trail-part-2/.
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