Using ND Filters
A Neutral-Density Filter, or ND filters, reduces the amount of light that comes through the camera’s lens.
The filters are like sunglasses and every filter is marked by a number. The higher the number, the bigger light reduction is. Which means less light comes to the sensor.
Under bright sunlight, an ND filter allows photographers more leeway in selecting an aperture and shutter speed by preventing overexposure. They are essential for all drone photography.
DJI for their drones: ND4, ND8, and ND16. The number associated with an ND filter indicates that how much light enters the lens in terms of a fraction.
- ND4 reduces light by 1/4. An ND4 filter can reduce 2 stops of light, allowing you to slow the shutter speed from 1/100s to 1/25s.
- ND8 reduces light by 1/8. An ND8 filter can reduce 3 stops of light, allowing you to slow the shutter speed from 1/200s to 1/25s.
- ND16 reduces light by 1/16. An ND16 filter can reduce 4 stops of light, allowing you to slow the shutter speed from 1/400s to 1/25s.
The ND as stated standard for neutral density which means that even though the light transmitted through the glass is less the colours are not affected and can be manipulated by colour correction as per normal.
Possible Effect of a Lower Shutter Speed
Drones like the Phantom 3 Pro and Inspire with the X3 camara have fixed aperture with Shutter Speed and ISO being the only variables available to get the best exposure. As drones fly high, this is increased because there is brighter light at higher altitudes.
If the light is too bright, camera increases shutter speed (less light comes to the sensor) and that way it compensates for the lack of ND filter.
With high shutter speeds a jello effect can become visible and this then creates a distorted image which does not look good.
The way to avoid this, is to use an ND (Neutral Density) filters on the camera. They reduce the light and that way camera doesn’t need to increase the shutter speed and you have more grace with the exposure level.
A lower shutter speed can create a motion blur.
If you used a weaker ND filter in this situation, you couldn’t achieve the same level of motion blur. However, if you chose a stronger ND filter, too much light would be kept out, your image would be underexposed, and your ISO value would need to increase accordingly.
So what ND filters you should choose depends on the amount of light around your and the effect you want to achieve.
Optimal Camera Settings
The optimal camera settings for the Phantom 3 and Inspire 1 X3 to be used with any ND filters are:
- Sharpness : -3
- Contrast : -2
- Saturation: -2
These help to flatten the image and give the best results for post production editing.
The sharpness can be less for the DJI Mavic Pro, the optimal setting we have found is -1.
We will explain the best setting for the Phantom 4 Pro in another article as this drone camera does not have a fixed aperture.