Which nd filter to choose
They are very popular with Landscape Photographers as they allow us to blur moving subjects whilst keeping stationary subjects perfectly sharp. You can see an example of this in the sunrise scene below. Notice the distant mountains and foreground rocks are sharp but the waves on the sea are smooth. I created the effect by keeping the camera still on a tripod and using a Neutral Density filter to extend the exposure. The ND filter is a dark piece of glass or optical resin which is placed over the end of the lens.
They have the advantage of reducing the chance of light leaking around the edges of the filter when using very strong filters. The disadvantage is they can quickly cause vignetting with wide-angle lenses if you need to stack multiple filters together. The option preferred by most landscape photographers is the square slot in filter design. Here a filter holder attaches to the end of the lens using an adapter ring. The filters then slot into the holder.
Most filter holders are much wider than the lens which avoids vignetting, even when you combine multiple filters on a wide-angle lens. Filter manufacturers use either optical resin or glass for the filters. Optical resin tends to scratch easily, and the surface of the filters can become covered with micro scratches. These are very hard to see but when you try to shoot towards the sun, they produce lens flare. Glass filters tend to resist scratching but can shatter if you drop them.
This was one of the reasons I originally switched to Kase and recommend their camera filters. ND filters derive their name from the fact they are neutral. This is a common problem with cheaper filters which tend to introduce a colour cast that can ruin an otherwise great shot.
The effect is extremely visible and the images created with it can grab attention right away. Even though there are darker filters available such as a 16 and stop , the stop filter is often what people think of when talking about long exposure photography.
The image above is a typical example of how a stop ND filter can create a surreal look to the image. With the filter placed in front of my lens, I was able to use a shutter speed of four minutes to completely blur the lake and get a soft, dramatic look in the sky as the clouds were dragged out.
You can have a 3 stop filter, a 6 stop filter, a 10 stop filter, and a lot other densities. If you know how to work with stops, this is a very logical notification and easy to work with. It resembles the stops you can find with your shutter speed, aperture, or ISO setting. If you calculate the amount of light that is blocked, you end up with the second notification that is being used. A 3 stop ND filter can also be called a ND8 filter. This way we know a ND64 filter will block 6 stops, and a ND filter will block 10 stops.
These numbers are based on the logarithmic scale. A 0,9ND filter is a 3 stops filter, which will lengthen the exposure time 8 times. The logarithm of 8 is 0,9. The logarithm of 10stops filter is 3,0. To make it easy, every stop will be the same as 0,3. By dividing the notification on the filter by 0,3, you end up with the strength in stops.
Just try it out. The best filter to be used depends not only on the result you want to have, but also on the subject, and the time of day. The latter should be obvious. If you already have a exposure time of 15 seconds without filter, it would be foolish to use a 10 stops filter, because you will end up with a four hour exposure.
In other words, choose your filter to reach the wanted exposure time, instead of using a neutral density filter and just use the exposure time that comes with it. I always make a distinction between shooting large water surfaces, and streams and creeks, or even waterfalls. If you shoot large water surfaces, and you want to smoothen the surface completely, you often need an exposure of at least 30 seconds, and preferably longer. Exposures that can reach up to 10 minutes will produce great results.
Measure the amount of light, and calculate how many stops you need to hold to reach the desired exposure time. A 10 stop or even 15 stop filter should do nicely. Perhaps a six stop filter if you shoot in darker conditions. But if you are at the coast, and you have a really nice surf, you will probably be better off with a shorter exposure.
This way the dynamics of the waves will be visible in the photo. A shutter speed between 0. In that case you could do with a 3 stop filter, or a 6 stop. You want to shoot the clouds, waves, and people in slow motion, but you are unable to do that even with the widest aperture and the lowest ISO. Take the portrait in bright light with a wide aperture.
Even with the lowest ISO and the highest shutter speed, your image still gets overexposed. The exposure is controlled by the nd filter so that the depth of field aperture and ISO will stay the same.
ND8 lens filter. The advantage of the circular ND filter is its convenience. You can screw on your camera lens with no light leaks and less vignetting.