45

A sheet of glass or plastics will typically have internal stresses. For glass and some clear plastics these lead to the birefringence patterns you see, when you shine (partially) polarized light on them and then view them through a polarizing filter. You can try this out by either using two polarizing filters, one in front and one behind, or holding such an ...


28

I got a little carried away with formatting my answer... This drawing is adaptable and can automatically calculate different scenarios, I'll give LaTeX/Python source to anyone who wants it. Edit: I've put the source code here. I must warn potential viewers that it's difficult to read and badly formatted because of nesting python inside LaTeX.


14

This picture is a composition of slices of many photos taken from different heights, likely from a drone. The key to understanding it is to examine the camera's perspective or point of view from different horizontal slices of the composited image. For approximately the bottom quarter of the image, the camera is below the roof lines of the buildings at the ...


12

Drone do not curve images. Camera lenses do. You can mount different types of cameras or lenses on a drone but many models now have their own built-in camera which usually incorporates a small fisheye lens. This allows them to have a huge field of view and so they do not need to fly very high to see an entire scene.


10

A sufficiently fast shutter would do it, but that also may very well not be a satalite photo. Google maps also uses arial photos and the detail of the plane in the photo seems too high and the plane too large in comparison to the ground for it to be taken from space. My guess is that the photo was taken from another plane, probably moving in a similar ...


10

Do the math. Let's say the plane is moving at 200 MPH, which is a plausible value right after takeoff or right before landing. Note that the flaps are extended, so one of these is the case. 200 MPH is 89 m/s. There is some blur. I'd say about 250 mm or less motion of the plane during the picture is about the limit that picture is showing us. That would ...


7

Very early color reconnaissance cameras did, in fact, use a color wheel in front of a camera with B&W film. At that time the resolution available with B&W was superior to that of color film. Developing labs that could easily process B&W film were also already in place at the air bases from which such cameras were flown. The resulting images were ...


7

A quick Google found me this page, where it says: "Russian photographer Sergey Semenov shows you the NYC Central Park the way you’ve never seen it before. The amazing picture that won Semenov the best amateur award from the International Pano Awards, is stitched together from a bunch of 360-degree panoramic pictures, taken from a helicopter." Once you've ...


6

Here are some possible sources of error: Manufacturer stated focal lengths are often rounded favorably or sometimes plain exaggerated (e.g. a 200mm might well be only 190mm). Focal lengths are also stated at infinity focus, lenses change focal length when focusing (though it is more common for a lens to get wider as you focus closer not narrower). Sensor ...


6

I hope it is obvious that the heavier side of the balloon will swivel to the bottom. Even if your camera is amazingly light, you will need a counterweight to balance that — something slightly heavier than the camera is the easiest. (You could also do several weights distributed in a balanced pattern. But either way: more weight!) Once you have the ...


5

None of the GoPro cameras can geotag photos. Because they don't have GPS built in, or any way of connecting to a separate device. The GoPro app does not support geotagging. So your aerial photos will not be geotagged. But you can geotag them afterwards. ie use a GPS device to record a tracklog, then sync this with the timestamps of the photos. There is a ...


4

Satellite photos are often taken that way, with multiple linear sensors ("push broom scanners") that each detect different frequencies, mounted in such a way that they pass over a given point on the planet's surface at slightly different times. If it's an aerial shot, that's weird.


3

draw VERTICAL lines through selected landmarks in your photo draw lines through the same landmarks on the map and find the crossing point repeat using more lines and more landmarks for better precision this simple method does not give you any information on the altitude - just fly up until your picture starts to look right :)


3

For non-wide-angle lenses, and subject distances much larger than the lens's focal length (your use-case certainly applies), the imaging system obeys the following basic equality: (distance to object, d) / (size of object, O) = (focal length, ƒ) / (size of image, i) This follows from the relationship of similar triangles as shown below: Thus, ƒ = d * i / ...


3

The K-20 was near ubiquitous among U.S. Army Air Force units that did any kind of photographic reconnaissance. You'd literally be looking for a needle in a haystack. It's highly unlikely you could use the serial number to trace the camera from the manufacturer to a unit that might have used it. It's more likely that you might find the serial number in ...


3

Looking at the specs of the DJI Phantom 3 and 4, the lens is described as: FOV 94° 20 mm (35 mm format equivalent) f/2.8 Focus at ∞ The Phantom 2 on the current DJI website comes with a GoPro Hero4 Black, which (if you're shooting 16x9) has a 118.2º HFOV (the narrower fields of view settings are done by cropping). So, I'd say that, no, it's ...


2

In engineering we call the optical center on the image plane "principal point". But that would be where the point you are looking for is projected. We dont have a name for that point in the natural domain.


2

As AJ Henderson has said, a fast enough shutterspeed is the answer. To put some numbers onto it - shooting at an airfield, if you have a King Air 350 coming in to land, you want your shutter to be around 1/320s or slower for propeller spin in the image, as otherwise you freeze the propeller in mid air. A propeller also spins quite quickly so freezing a ...


2

Fisheye went out when the Phantom 3 was released. The Phantom 3 & 4 have rectilinear wideangle lenses with no fisheye distortion.


2

It does not seem to be substantially different from standard CMOS sensor other than the fact that most Illunis cameras seem to be based on CCD rather than CMOS chips. The three color bands centered on 450nm, 550nm. and 625nm are certainly similar to most Bayer masked sensors in consumer cameras. What it does seem to be substantially different from is other ...


2

According to this article, each image is made of between 18 and 20 photos taken from a drone. It does not say what happens to the sets of images but it would most likely be a software process that works similarly to panorama stitching.


1

I would recommend looking at single axis solar tracker designs for the mechanical design. These will be some form of motor connected to a plate (Where the camera could mount) that get close to 180° rotation of that single axis. You will then want an Arduino with a gyroscope sensor like the MPU-6050 to detect the current orientation of the plane. The Arduino ...


1

Not sure if there's much you can do. The airplane is moving so you have to keep shutter speed up, and theres not much light to work with. Only thing you could do is upgrade your equipment. Go buy a fast lens like an f/1.8 or faster.


1

The images are DNG, so they undergo processing by Adobe. Most likely, there is an auto white balance set (or another colour setting), and it can easily be inconsistent, esp. in such difficult conditions. Try to select all images and enforce a specific manual white balance and other settings, so that there were no 'auto' anywhere.


1

While calculation should be possible, I would rather recommend trial and error to begin. Start with your drone filming as it ascends. Then take screenshots from still-frames from the video. Do your stitching and see whether your image looks good to you. If so, make a note where in your video clip you took the screenshots. If your drone ascends slowly at a ...


1

If I were going to calibrate a drone's image "footprint," assuming that the camera reports the gimbal angles (otherwise you have no way to make a measurement), I'd either hang or hover the drone over a calibrated target, such as tape marks on a driveway. Then take a few pictures at different gimbal angles and identify the image area covered by the tape ...


1

It is not an "effect". It is the lens most small action cameras use. Why? Because you normally do not use a viewfinder, or tripod. You intend to take aerial views, landscape, etc. A normal drone is not a spy cam.


1

Well, now you just need to google drone telephoto images. Itai pointed you. If you mount a wide angle (or a super wide angle lens) you have that field of view. The technical problems for cheaper drones or general public ones, to achive tighter shoots are 3. 1) If you do not have a wide angle lens, you need to be more specific where are you poinging at. It ...


1

Yes. The regulations are a bit odd, but as you are travelling to Europe, I will refer you to the UK regs: http://www.britishairways.com/cms/global/pdfs/lithium_battery.pdf In essence you need to declare anything over 100Wh and cannot transport anything over 160Wh You cannot put spare packs in the hold, if you put the copter in the hold with a pack ...


1

If you have overlapping areas and can set control points, it should work nevertheless. The resulting FOV may be incorrect (it is ill-defined in Hugin anyway) but this does not mean a bad output. The resulting FOV is accurate only if you have a 360° panorama.


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