# Is it possible to make a photo of a plane at cruise altitude with this zoom?

I came along to this photo of a plane flying at cruise altitude. I was really surprised by the level of detail and zoom this photo has. You can even see the tail number of the plane!

Is it really possible? For curiosity, what kind of equipment is needed?

• One does not need zoom for that, fixed focal length is enough. Commented Apr 10, 2016 at 9:10
• Interesting... Are you referring to photos captured from the ground? Or from another plane? This photo was captured from the ground I think.
– user50415
Commented Apr 10, 2016 at 9:19
• zoom is not equal to magnification, zoom means "variable FoV", "variable magnification". Big focal length (small FoV) is what one needs for this photo, not zoom. Commented Apr 10, 2016 at 9:20
• I do not think that is cruise altitude. That altitude is above the couds. That plane is forming a tail of water, which, I think forms at lower altitudes. Commented Apr 10, 2016 at 14:10
• @Rafael Jet planes leave vapor trails at cruising altitude all the time. Commented Apr 10, 2016 at 14:21

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.

• Thank you for the detailed answer. I redid the calculations using effective distance from ground and I got 3600mm. Is it something that can exist in a photographer selection of tools? I am always referring to photos captured from the ground.
– user50415
Commented Apr 10, 2016 at 13:29
• A pro might have a lens of maybe 2000 mm, but that's probably not what happened for this shot. Understand that a picture is for example 5600 pixel wide; your example shot has the plane at about 900 pixel, which is only 1/6 of the picture. So you save a factor of 6, and you are back to 600 mm, which most people can reach with a 100-$-tele-converter. Commented Apr 10, 2016 at 13:35 • if you look for extremes, check popphoto.com/gallery/… (1200 mm). There is also a sheikh who got a 10000 mm lens built, for over a million$. Commented Apr 10, 2016 at 13:38
• You also need a good support. A sturdy tripod. Commented Apr 10, 2016 at 14:12
• There are no commercially available 2000mm photographic lenses. The Air Force, CIA, and NSA and their international counterparts may have a few for high altitude and satellite recon, but no "pro" photographer that I've ever met owns a 2000mm photographic lens. For all practical purposes there's no such thing. Commented Apr 10, 2016 at 16:40

Is it really possible?

Yes.

For curiosity, what kind of equipment is needed?

A very long focal length - or another plane.

• ... and a good weather. Commented Apr 10, 2016 at 8:57
• how long is very long? Commented Apr 10, 2016 at 9:43
• @Pinhollow Euri not just "good weather", but more specifically, low levels of atmospheric haze. Oftentimes, that happens after heavy rain - at least where I live. Commented Apr 10, 2016 at 9:45
• "Good weather", while perhaps necessary, does not fall under the "equipment" label. Commented Apr 10, 2016 at 10:30
• @osullic How high is the plane flying? Commented Apr 10, 2016 at 10:30

1800 mm lens is the right answer for the 20000 feet, but remember, this represents a 400 foot wide field, and the plane is traveling maybe 500 MPH. That's 733 feet/second, so it will cross the field of view in about 1/2 second, and it will be quite difficult to find it in the viewfinder in the first place. Nothing about it will be easy.

You can buy a 2000mm telescope (Celestron 8" class) for maybe \$1500 US, including a tripod mount and camera mounting, and a finder scope to help aim it (works for astronomy too). Optical quality will not match a photo lens that costs many times more, and it doesn't have camera features like stops (it will be about f/10), but it could take that picture, possibly more conveniently than a camera lens (still NOT easy due to the motion). You could position ahead of the plane, and then wait for it to arrive, and hope you could catch it.

There is a calculator what will do the math for a 400 foot field at 20000 feet for various camera sensors, option 5 at http://www.scantips.com/lights/fieldofview.html