Can you photograph an airliner at cruise altitude with enough detail to read the tail number?
Asked 4/10/2016
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2 answers
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I saw a photo of an airliner at cruising altitude with surprisingly high detail—you could even make out the tail number. Is that really possible from the ground, and what kind of focal length or equipment would be needed to capture a shot like that?
Originally by user50415. Source · Licensed CC BY-SA 4.0
user50415
10y ago
2 Answers
7
Do some simple math: Assume the plane is 20000 feet away, and 200 feet long. Let's also assume you want to fill half the frame width (in a full-frame camera), which is 1/2 of 36 mm = 18 mm.
With B/G*d = f (where B is the size in the picture, G the size of the object, and d its distance), you get:
f = 18mm/200ft*20000ft = 1800 mm
An easier to remember way (I think) is to divide object distance by object size: 20000ft/200ft = 100, and that's the factor you need to multiply to the size you want on the picture.
1800 mm is out of the normal photographer's lens selection, but you can buy that. Probably a 600mm with two teleconverters is the cheapest way. Of course, you can also go for only 1/12 of the picture = 3 mm and you will need only 300 mm which most people have. Then you crop the picture down and still have enough resolution.
Note that I made wild assumptions about the size and distance of the plane. Make your own assumptions to get your own results.
Originally by user46784. Source · Licensed CC BY-SA 4.0
user46784
10y ago
0
Generated from our catalog & community — verify before relying on it.
Yes, it’s possible, but it’s difficult. The main requirement is a very long effective focal length.
Using simple magnification math: if a plane is roughly 200 feet long and about 20,000 feet away, you’d need around 1800mm on a full-frame camera for the aircraft to fill about half the frame width. A shorter lens can still work if you’re willing to let the plane occupy a smaller part of the frame and crop later—for example, around 300mm would make it much smaller in-frame, then cropping does the rest.
In practice, people might use a super-telephoto lens with teleconverters, or even a telescope attached to a camera. A telescope can provide the needed focal length, though it may be slower (for example around f/10) and less convenient than a photographic lens.
The hard part isn’t only magnification: a jet at cruise speed crosses a narrow field of view very quickly, so finding and tracking it is challenging. Good atmospheric conditions also matter a lot, because heat shimmer and haze can destroy fine detail long before lens sharpness becomes the limit.
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AI10y ago
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