Ok, so it's not one of the great debates of the photographic world, but the humble ND filter (or neutral density filter) has been an important part of the photographer’s kit bag for a very long time.
Variable NDs are the new kids on block, and are a relatively divisive subject, and as is often the case – the pros and cons divide up into quality v convenience.
Consider this: sometimes having a good grasp of sunset photography can provide you with a decent preparation outline for taking ND filters out into the field. That's where we have a great course on offer – Amazing Sunset Photography – for you, including modules such as “Long Exposure Technique”.
With neutral density filters becoming ever more popular its time to look at not only what an ND does but also which is most suitable to you.
What Is An ND Filter?
Many of you will know this but to newcomers to photography, an ND is a piece of dark glass or acrylic that we put in front of our lenses to reduce the exposure.
There may be many reasons for doing this, allowing a wider aperture in bright light, slowing down shutter speed so that a flash will sync or most commonly slowing down shutter speeds to blur motion such as a waterfall.
Neutral Density filters are also used in video making where it is important to keep the shutter speed low.
Traditionally these filters reduce exposure by fixed amounts,
- 1 stop,
- 2 stops, and
- 3 stops.
Beyond that, the ultra ND filters reduced exposure by 6 stops and 10 stops. More recently we have seen the arrival of the variable ND filter. These are effectively two polarising filters sandwiched together and work like using a single polarizer. By turning the front element, you decrease or increase the amount of light passing through and hence have more control over the amount of light you wish to decrease.
The Fixed ND Filter:
Let's Look At The Advantages And Disadvantages Of Fixed ND Filters
These filters can come in 2 forms:
- Ones that screw directly to the front of your lens,
- Ones that are part of a square filter system.
We have looked at the difference between the two here.
- The two main advantages of using fixed ND filters are cost and quality. The price of a single ND filter is significantly cheaper than a variable and will also be significantly better quality than cheaper variable NDS.
The quality comes not only from the materials used but also the fact that the light is only passing through one modifier, not two.
- The main disadvantages are that you will need several different filters to have a complete set of NDs and if you go for the screw in type you will need to either duplicate that set for each different screw filter diameter on your lenses or buy step down rings so that they fit.
- The other disadvantage is convenience, particularly if you want to change to a different ND when using the screw in type of filters. This can be a slow and cumbersome process.