I'm puzzled about why most of the buildings are tilted while the horizon is straight.It's a single photo (not a panorama).
Can it be corrected with Photos or Photoscape on a mac ?

The horizon is level. I think it may be related to the yaw of your spark. Please try to shoot more photos with correct direction and see if the building are tilted.

I think a found it out myself, using photoscape (free version), doing perspective correction and crop.
The perspective slider is moved all the way to one side. It almost fixed it.

Looks good! (the edit)

This is a normal behavior. If a camera (any camera) is not horizontal then the perspective shows up. It is just a basic geometry. In your case the camera is pointed downward, hence the lines, that would be vertical with level camera, converge below the picture. If you point a camera upward (not possible with Spark, but can be easily done with any "normal" camera) the "vertical" lines will converge above the picture. It is more evident with wide-angle lenses (and the Spark's lens corresponds to 25mm on FF) than with tele-lenses, yet it will occur always. As said, it is just basic geometry. Being humans, we are used to perceive vertical lines as vertical. That is because we are not birds. We are used to look more or less straight ahead. A bird would probably say that the second version looks strange :-)

BTW, I could give you a precise mathematical proof and explanation, but it may be hard to digest :-)

Thanks! That made me play a little with a 12-24mm dx nikon lens.
The effect is obvious at the 12mm setting.
Next time, I will try to fly lower.

_pk Posted at 2017-10-21 04:31
This is a normal behavior. If a camera (any camera) is not horizontal then the perspective shows up. It is just a basic geometry. In your case the camera is pointed downward, hence the lines, that would be vertical with level camera, converge below the picture. If you point a camera upward (not possible with Spark, but can be easily done with any "normal" camera) the "vertical" lines will converge above the picture. It is more evident with wide-angle lenses (and the Spark's lens corresponds to 25mm on FF) than with tele-lenses, yet it will occur always. As said, it is just basic geometry. Being humans, we are used to perceive vertical lines as vertical. That is because we are not birds. We are used to look more or less straight ahead. A bird would probably say that the second version looks strange :-)

BTW, I could give you a precise mathematical proof and explanation, but it may be hard to digest :-)

Great explanation.

heliman Posted at 2017-10-21 05:30
Thanks! That made me play a little with a 12-24mm dx nikon lens.
The effect is obvious at the 12mm setting.
Next time, I will try to fly lower.

Try both. I really like the bird eye's perspective and the unnatural looking perspective to our eyes.

I usually divide the scene before taking a photo inorder to avoid the lens distortion by keeping 1/4 - 1/3 for the sky.

This was after so many tests I've done.

In case of ground scene only, the same percentage should be for an open area without tall buildings.

Thanks!
The camera was pointed down to make the autoexposure lighten the ground.
I should have set the exposure manually.

_pk Posted at 2017-10-21 04:31
This is a normal behavior. If a camera (any camera) is not horizontal then the perspective shows up. It is just a basic geometry. In your case the camera is pointed downward, hence the lines, that would be vertical with level camera, converge below the picture. If you point a camera upward (not possible with Spark, but can be easily done with any "normal" camera) the "vertical" lines will converge above the picture. It is more evident with wide-angle lenses (and the Spark's lens corresponds to 25mm on FF) than with tele-lenses, yet it will occur always. As said, it is just basic geometry. Being humans, we are used to perceive vertical lines as vertical. That is because we are not birds. We are used to look more or less straight ahead. A bird would probably say that the second version looks strange :-)

BTW, I could give you a precise mathematical proof and explanation, but it may be hard to digest :-)

Great explanation however, if you are flying in Tripod mode you can manually tilt the gimbal +30 degrees upwards on the Spark. It also tilts upwards automatically to take pano's.

_pk Posted at 2017-10-21 04:31
This is a normal behavior. If a camera (any camera) is not horizontal then the perspective shows up. It is just a basic geometry. In your case the camera is pointed downward, hence the lines, that would be vertical with level camera, converge below the picture. If you point a camera upward (not possible with Spark, but can be easily done with any "normal" camera) the "vertical" lines will converge above the picture. It is more evident with wide-angle lenses (and the Spark's lens corresponds to 25mm on FF) than with tele-lenses, yet it will occur always. As said, it is just basic geometry. Being humans, we are used to perceive vertical lines as vertical. That is because we are not birds. We are used to look more or less straight ahead. A bird would probably say that the second version looks strange :-)

BTW, I could give you a precise mathematical proof and explanation, but it may be hard to digest :-)

Thanks for the explanation.

heliman Posted at 2017-10-21 02:35
I think a found it out myself, using photoscape (free version), doing perspective correction and crop.
The perspective slider is moved all the way to one side. It almost fixed it.
[view_image]

Nice editing job