I was at my parents' house. I was in the garden. It was 7 PM. At this moment I decided to take a movie of the sky with my iPhone in slow motion mode. I took a section of the sky randomly. I've recorded for more or less 10 sec. I didn't notice anything at this point. Sky was a bit cloudy.When I took a look at the video, I saw the UFO. At normal speed (24 fps), it is very hard to see it. In short, at normal speed, the UFO is invisible. When the iPhone started the slow motion (240 fps), I noticed the object clearly. It is a grey/black dot. It seems to fly at the level of clouds. This UFO motion is quite strange and it moves very fast: 10 times quicker in the reality than the video. First I thought: "it's a kind of fly front of the aperture." When a friend of mine told me that the dot color is changing from grey to black and vice versa. Meaning that the object is flying at the clouds level. Clouds are affecting the object coloration seen from the land.Then I checked several times the iPhone to see if there is a bug or malfunction that affects the camera. But my iPhone seems ok.Now I would like to know more about this dot. I am a very open minded person and ready to hear a rational or paranormal explanation. If someone can analyze the coloration of my movie to determine the distance between the camera and the object, that could help a lot.Recommendations:Please open the video file in full screen mode. When the slow motion starts, the dot appears basically in the middle of the screen.It makes few loops and goes out of the frame from the left and low side.