Ultra HD (4K)
The ability of the camera to shoot Ultra HD 4K video.
This format covers several resolutions in which the horizontal frame size is approximately 4K pixels. The most popular in action cameras is 3840x2160 (twice the FullHD frame on each side), but there are other options — for example, 3840x1920, corresponding to an aspect ratio of 2:1. In general, 4K is a kind of successor to Full HD: among HD standards that surpass Full HD, UltraHD is the most popular, in particular, many advanced TVs are produced with 3840x2160 screens. On the other hand, this format is quite demanding in terms of processing power and memory, so it is relatively rare in action cameras, mainly among premium models.
Another important parameter given in this paragraph is the frame rate. The higher it is, the smoother the movement in the frame will be, and the details in dynamic scenes will be visible clearly. However, in UltraHD mode, most modern action cameras produce a very low frame rate — most often
30 fps, and in some models
24 fps or even
15 fps. This video is quite viewable, but fast movement in the frame may look blurry. There are cameras capable of shooting UltraHD at a solid speed of
60 fps — the blurring effect during such shooting is almost imperceptible. However, such a model cost is high.
Slow motion
Frame rate supported by the camera when
shooting in slow motion.
In general, such shooting is called “high-speed” because it is carried out at an increased frame rate (more than 60 fps). As a result, when played back at normal speed (60 fps and below), the video looks slow hence the name. This kind of slow-motion can be used just for fun, as an artistic technique, and even for scientific purposes — to capture movement that is too fast for the human eye. In any case, the higher the slow-mo frame rate, the more you can slow down the video and the more advanced the camera is in this regard. On the other hand, the higher the frame rate, the more performant the graphics part should be; and this, in turn, affects the price of the device, sometimes quite noticeably.
We also note that slow-mo shooting may be available only at certain resolutions, not always at maximum. These points can be directly specified in the specs of the action camera.
Aperture
Action camera optics aperture. This characteristic determines how much the lens weakens the light flux passing through it. This parameter is indicated by a fraction, for example, f/2.8. The smaller the number in such a designation, the higher the aperture ratio and the more light the lens can transmit. A high aperture ratio is important, first of all, when shooting in low light conditions: it allows you to capture an image without “raising” the sensitivity of the matrix and without creating additional artefacts in the form of noise, and in photo mode, it also allows you to work with shorter shutter speeds (which is useful for dynamic scenes). In addition, the higher the aperture ratio, the lower the depth of field and the easier it is to get a blurred background. Note that for simple shooting scenarios, this parameter does not play a decisive role, but for professional tasks, it can be very significant.
Photo resolution
The maximum resolution at which the action camera can take photos. Specified in pixels horizontally and vertically.
This parameter is directly related to the resolution of the image sensor(see above): the total number of pixels in the photo, usually, corresponds to the number of pixels in the sensor. For example, a photo resolution of 4608x3456 corresponds to a sensor of 15925248 pixels, or approximately 16 megapixels. If the number of pixels in the photo is greater than the claimed resolution of the sensor, then the manufacturer uses software tricks that allow you to improve the photo resolution to a higher one than originally. This reduces the cost of devices but also affects the quality of images.
Theoretically, high-resolution images can provide good detail, but in fact, much depends on the specs of the sensor (primarily physical size) and image processing features.
