Knowing your ND Filter Systems
For some time now, I wanted to put a blog together about ND Filters as occasionally I receive emails asking which ones I recommend purchasing. To answer this question, I first need to address a few topics related to ND Filters in general. I will not be addressing specific brands but will give pro and con arguments for the two different ND Systems. Keep posted for Part II of this blog in which I will be showing performance examples of different brands of ND Filters.
Let me start with the statement that I am not getting sponsored by any brand or company to advocate for their system or product. Everything you read here is from my personal experience or from those of my colleagues, students and fellow photographers.
An important consideration to keep in mind regardless of brand and should be your first consideration when purchasing ND Filters, is: ‘What is your personal style?
There two types of filter systems:
Circular: filters that thread on your lens and to one another
Square: filter that are individually slotted to fit in a holder
I will elaborate here on the pros and cons of each system.
A. Circular – Pros:
No light seepage when shooting long exposures
I personally like shooting with this system as all my 77 mm fit in my filter pouch bag that straps onto my belt. This way I have comfortable and easy access to the filters. I do wish they would create different coloured rings for each f-stop filter. This would make life easier when pulling out a filter, they would be colour coded and you wouldn’t need to read the fine print on the ring each time. I paint my filter rings with coloured nail polish to differentiate between them in my filter bag.
Circular – Cons:
Threading the filters on the lens can be a drag, especially if you are not shooting with a prime lens and chance the risk of changing your focal length as you thread them, not to mention having them drop while you thread. One way that I found to overcome this (in specific situations) is to use the XUME magnets - they are amazing for what they do. Just thread one magnet ring on the lens, the other on the filter and now just place the filter gently, it will snap into place without any hesitation. The one caveat: when you are threading two filters when shooting with a wide-angle lens, any addition to the lens can cause vignetting. I have yet to find a way around this.
Thread two filters together lightly and with caution as some people (dare I say men…) tend to over tighten them and then, well, good luck trying to separate the two filters now.
B. Square – Pros:
The filters sit on slots and can be placed in and out of these slots with ease.
If you are shooting Long Exposure, you can even add to the ND filters an additional Graduated filter. This will help in darkening the bright sky and create an artistic looking vignette in the sky. Furthermore, with the holder system you have the flexibility to move your graduated line up and down the horizon line as needed according to different light situations and compositions. With the circular system, you are stuck with a graduated filter that has the horizon in the middle of your lens.
Square – Cons:
Many filter holder systems are VERY prone to light seeping between the filters placed in the holder and thus creating ghosting or other unwanted light features during Long Exposures. You can overcome this by adding tape or dark cloth around the top of the filters.
This system is a bit more cumbersome to work within the field. With the circular system, I can take my shots without having to place my camera bag down on a surface and spread out all my ‘stuff’. This comes in handy when I’m shooting knee deep in water or on steep terrain. With the holder system, it’s pretty much impossible not to have to spread out your bag to access your equipment. If you find that you always place your bag down and ‘settle’ into a location you are shooting, then this would not be a problem for you.
2. Brass ring vs. Aluminium ring
Circular filters have a ring around them that is threaded onto the lens, or from one filter to another. This is useful for increasing the ND strength, i.e threading a 10 f-stop filter with a 6 f-stop filter will result in 16 f-stops.
Brass rings are more durable and add to the longevity of the filter which reflects at a higher price point. The aluminium ring filters are still very good, however, if dropped on a hard surface can dent more easily than the brass ring (hopefully the glass won’t break first!). This is a consideration you need to ask yourself, do you tend to drop, slip or shoot in rigorous conditions where you will need a more durable filter? Or, are you always carefully place your filters on their corresponding containers carefully without the danger of them dropping or slipping.
3. Some rings are thicker than others, so when stacking two filters on extreme wide-angle results in vignetting. On the other extreme, some ND filters of 16 f-stop are paper thin so there is no danger of vignetting. An easy way to overcome this issue is to purchase a large diameter filter and use a step-down ring for your lens. I was shooting with two 77 mm filters threaded together, a 6 and a 10 f-stop on a 72-diameter lens at 10 mm (cropped sensor Fuji X-T2) and I still had some vignetting. I would recommend purchasing the 82 mm to eliminate vignetting all together.
4. Colour Cast
This is quite a big issue with ND filters. Most of the filters will have some sort of colour cast. If you shoot for a final black and white image or don’t mind fixing the colour balance in post, then that shouldn’t be a problem as post-production is such a key phase within the complete Long Exposure process. However, it is something to consider.