Why are CPL or /PL Spark lens filters needed?

Because DJI Spark filters used on a drone are associated with large restrictions on the shooting angle. This is a professional shooting tool for those who have the understanding and the time to experiment. With ND filters DJI Spark, it is much easier to spoil shots than to improve them. Diagonal darkening or generally lightening the sky and darkening the ground, black water surface, and other unexpected effects are much more difficult to fix in post-production, because. The effect changes as the shooting angle changes. But it is quite possible to add a polarization effect when processing video, and even more so photos in RAW. In editors, this is called haze removal.

How to choose the ND filter for DJI Spark?

Before buying a DJI Spark ND filter, and even before buying a drone, you can estimate the degree of filter darkening you need. To do this, take your phone and look at your photos from those places and those conditions in which you intend to use a drone with a filter. Open the photo properties and look for three parameters: aperture, shutter speed, and ISO. If the ISO is greater than 100 or the shutter speed is less than 1/200, then the filter is definitely not needed. Next, you need to compare the aperture of the drone with the aperture on the phone. Usually, on phones, they put fixes around f / 2, and on DJI drones f / 2.8. This means that the shutter speed on the drone will be 2 times longer. We take exposure from a photograph, for example, 1/800. We multiply by 2 if the phone has f / 2 (by 4 if f / 1.4, do nothing if f / 2.8, divide by 2 if f / 4, and so on f / 8, f / 16). The resulting figure is the estimated shutter speed of the drone. In our case, we get 1/400. Further, everything is simple. If we want a shutter speed of 1/50, then we need ND8.

The number at ND shows how much the shutter speed will decrease when using this filter. Often on a sunny day at f / 2.8, you can see shutter speeds of 1/3000 and higher. In this case, without using DJI Spark ND filters, a strobe effect appears when the camera moves. The edges of objects flicker, the image breaks, and it is difficult for the eye to maintain focus.

If the scene involves alternating dark and light areas, then you need to start from the middle ones. You need to understand that in dark areas, to compensate for the lack of light, the camera will increase the ISO, and this can lead to noise. On the other hand, the overexposure of the area can no longer be corrected (it is impossible to reduce the ISO). Therefore, fixing the shutter speed in most cases is not necessary. Let automation have two degrees of freedom – ISO and shutter speed. If the camera has an aperture change available, then on the one hand (for the camera) it is easier, on the other (for us) it is more difficult. The aperture will help the camera with an excess of light, but deviating from the optimal values \u200b\u200bis detrimental to image quality. Only very expensive lenses have good uniformity across their aperture range.