Purchasing Neutral Density Filters
The Essential Accessory for Photography
Why not also sign up for my free photo guide offer?
This might sound straight forward but it’s amazing how many people I speak to who have wasted money buying the wrong filters. Here is my summary of what to look out for when choosing filters. I hope it saves you some frustration and money.
I should probably start by saying something about why Neutral Density or ND filters are so valuable to photographers despite all the advances in digital. In short they allow you to control the light reaching your cameras sensor which allows you to control the exposure. Two broad categories exist, the full ND filter where the whole of the filter restricts light and the Graduated filter (grads for short) where only part of the filter restricts light. The Neutral Density indicates that they are a neutral colour and should not have any visible impact on the colour of the final image.
You would typically use an ND filter to lengthen shutter speeds for a particular aperture so that movement is blurred. An example might be when photographing a waterfall or the movement of waves. Although some camera manufacturers are now starting to build ND filters into their cameras, most of the time selecting the lowest ISO possible simply won’t give the sorts of duration that can be achieved with a ND filter. The strength of these filters tends to be measured in stops indicating how many stops they reduce the light by e.g. 3 stops, 8 stops and even 10 stops. Remember also that each stop of light you lose doubles the length of the shutter speed. By the time you have lost 10 stops of light you could be looking at shutter speeds of minutes, even in the middle of the day.
NG Grads are used to reduce the exposure of a specific area of the image e.g. the sky in a landscape to help balance exposure across the image. In a landscape for example, reducing the exposure of the sky allows the ground to appear brighter. Without using an ND Grad the ground would appear too dark or the sky too light. Even on a good DSLR, camera sensors currently have between 10 and 12 stops of latitude meaning the difference between the darkest point they can measure and the lightest point is only 10 stops. This is much less than your eye and also less than many of the scenes you come across and want to photograph. By reducing the difference in exposure between the brightest and darkest areas of the scene we improve the ability of the camera to create a good exposure. Again the strength of these filters is measured in stops but I will cover this shortly.
Round or Square
For both types of filter there are two options; screw on circular filters that screw on to the front of the lens or Square filters that slot into a filter holder that attaches to the front of the lens via an adapter. My personal view is that for ND filters the screw in types are better as they reduced light entering the lens from the top and bottom of the filter as can happen with the square filters. The drawback with the screw in filters is that if you need to use more than one the edge of the filter ring can cause vignetting around the edge of the image. You might therefore need more choice in terms of strength of filters than with a square system where you can slot two or three filters into the holder to give more of a light reduction. You might also find that some of the stronger filters e.g. the Lee big stopper 10 stop filter is not available as a screw on filter.
For NG Grads I wouldn’t recommend anything other than a square type filter. With screw in graduated filter it’s almost impossible to compose the image and also line up the gradient part of the filter with the horizon. You might get lucky now and then but generally you will find yourself making compromises all the time. Using a square filter format you can compose the scene and then move the filter up or down in the holder to line up the gradient so that it can’t be detected in the final image. It’s also possible to stack two or three filters to give a stronger reduction although you need to be more careful when doing this as it becomes easier to detect the filters.
In addition to purchasing the filter you will need to buy a filter holder which attaches to the front of your lens using a filter adapter ring. The ring screws onto the thread on the front of the lens and then the adapter attaches to the ring. As different lenses tend to have different filter sizes you will need to buy different sized adapter rings. Some filter adapter rings such as those used for the Cokin and Hitech filter systems are simple metal disks and quite cheap. The Lee filter rings are a little more complex due to the design of the lens holder but have the advantage that they come in both standard and wide angle designs. If you with be using the Lee system with a lens of 24mm or wider I recommend buying the wide angle type adapter. Whilst they are around twice te price, the design moves the filter holder a little closer to the lens to reduce the chance of the filter holder being seem around the edge of the lens.
The downside to screwing an adapter ring onto the front of your lens is that the lens cap tends not to fit (however the Lee Standard rings usually do allow for a lens cap). I have found that both Cokin and Lee sell a filter cap which is a plastic cover fitting over the adapter ring helping to protect the lens from dust whilst allowing the adapter ring to remain on the lens. I tend to leave my Lee filter rings on the front of my Canon and Pantax lenses as constant screwing and unscrewing is time consuming and wears the threads. Snapping a plastic cap over the front is then really easy.
ND Grads come in a variety of strengths indicating how much light the dark part of the filter will remove. A 0.3 will remove 1 stop of light, 0.6 two stops and 0.9 three stops. Some manufacturers such as Format Filters also produce a 1.2 which removes 4 stops. Lee also produce a 0.45 (1.5 stops) and 0.75 (2.5 stops) but I would only bother with these if you are shooting slide film and need to get the exposure exact.
If you can afford it, it’s better to buy your graduated filters in sets as this tends to be cheaper than purchasing them separately. A typical set will have a 0.3, 0.6 and 0.9 filter. If you can’t afford a full set buy the 0.6 first as this tends to be the most useful. The 0.9 then tends to get the most use after the 0.6 and the 0.3 least. You could of course pair a 0.6 and 0.3 in the filter holder to create a 0.9 filter so you might consider this to be a better purchase.
As well as different strengths you might also find the filters you are considering are available in hard and soft grads. This refers to how short the gradient is between the dark and light area of the filter. Soft grads have a longer transition than hard grads and are more forgiving if you don’t light them up exactly. The benefit of hard grads is that they are easier to align because the transition is more obvious in the viewfinder. Personally I have both hard and soft grads as it makes combining two filters together easier if one of them is a soft grad. Soft grads might also be better for use where the horizon isn’t flat. If however you have limited funds I would start off with hard grads as they are also better suited to today’s cropped sensor cameras.
Finally you need to consider the size of your filters as each manufacturer will offer a range of sizes which tend to measure the width of the filter. The most popular sizes are 85mm and 100mm wide. All three of the main filter manufacturers found in the UK (Cokin, Lee and Format Filters) produce ranges of filters in these sizes. In addition to these there are smaller filter sizes such as the Cokin A series and Lee RF75 (75mm) as well as larger sizes such as the XPro or SW150 (150mm). Generally speaking don’t buy A series filters, they are just too small for today’s lenses. The Lee RF75 filters are 75mm wide but have been created specifically for use with Rangefinder cameras such as the Xpan so unless you have a film rangefinder camera you are paying a premium for something you don’t need. The best option for a DSLR is the 100mm filter with the 85mm filter being the next best. These tend to be wide enough for most lenses but the drawback is the 100mm filters are quite expensive. Having said that it’s better to have 1 filter that works well than 3 that don’t fit your lens properly.
From my own personal experience I have found the 100mm filter to be the most useful and versatile size. I do however have sets of 85mm filters which I tend to use with my GF1, LX5 and Xpan cameras. The smaller size of these filters makes them easier to handle on smaller cameras.
Now you understand the options, which manufacturer to go with is an important consideration. In the UK we really have three choices at present for square filters: Cokin, Lee and Hitech/Format Filters. The general opinion is that Cokin and Hitech are lower quality than Lee and this is reflected in the lower price. A common issue is that many of the cheaper, supposed Neutral filters will produce a colour cast and therefore aren’t Neutral. Before you write off a manufacturer based on price let me share some of my experience.
I have purchased sets of Cokin filters in the past which were Neutral. I have however had filters from the same company and found they have a slight red colour cast to them which comes in handy when shooting in the early evening and at sunsets. The problem therefore is lack of consistency.
Lee filters have tended to give a neutral colour cast under most conditions however I have also shot images where the filters made the sky look a tobacco brown colour. The other people who were with me at the time also had exactly the same result.
Hitech/Format filters have also been a good performer for me however with some of my cameras I have found a slight purple tint was produced. I have also experienced this effect with the Lee filters but less frequently. I can only conclude that the Camera must also have some impact on this which probably supports the mixed opinions about the results people obtain.
What I would recommend is that if you can afford to, purchase the Lee filters although they seem to have shot up in price recently. If you can’t or don’t want to afford Lee consider the Hitech/Format brand. If cost really is the deciding factor for you pick Cokin.
For screw in ND filters I would select B + W if you have the funds. Hoya also make good filters and are less costly.
Final tip is to ensure you have the filters in a soft case or wrap them in a clean lens cloth. You can pay a fortune for filters and then scratch them on your first outing if not careful.
If after reading this article you decide to buy some filters please consider using the links below. I receive a small commission for purchases which I put towards the upkeep of this site. I am also happy to answer questions if you want to email me.
Lee ND Grad Sets
Hitech 100mm wide x 150mm tall set Hard
Hitech 100mm wide x 150mm tall set Soft
Hitech 85mm Hard Grad Set
Hitech 85mm Soft Grad Set
Cokin NG Grad Set
Lee Filter Holder
Hitech 85 Filter Holder
Cokin Filter Holder
Lee Wide Angle Adapter Ring
Cokin filter ring – (remember to order the right size)
Also works with Hitch filter holder
Lee Filter Ring Cap
Cokin Filter Ring Cap
B + W 10 Stop Screw in Filter
(remember to order the correct size an strength)
Hoya ND Screw in Filter
(remember to order the correct size an strength)