# How do I convert focal length to maximum distance?

I would like to know whether there is any relation between focal length and distance. For example, what is the max distance I can shoot from a 55mm-300mm lens?

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What do you mean by `max distance`? This is dependent on the subject you're photographing. The question now is unanswerable. – Saaru Lindestøkke Nov 15 '13 at 11:47
What do you want to shoot? People? Insects? Cars? Buildings? The Moon? – Håkon K. Olafsen Nov 15 '13 at 14:05
"How far away can it see?" is a weirdly common question about binoculars, telescopes, lenses, etc. I usually point out that your unaided eye can see as far away as other galaxies. – coneslayer Nov 15 '13 at 14:58
While coneslayer's point makes it immediately obvious why this question can't be directly answered, check out What is the formula for percent of frame filled at a specific distance and focal length? for a related question with a practical answer. – mattdm Nov 15 '13 at 16:50
No,there is not. – mpapec May 19 '15 at 9:12

The minimum and maximum focus distances have no direct relation to the focal length of the lens. All lenses have a minimum focus distance. For Macro lenses this is closer than for normal lenses (is the main part of what makes them Macro).

The majority of lenses have an infinite maximum focus distance (focus at infinity). Under certain conditions however, such as the use of extension tubes, it can become impossible for the lens to focus at infinity. In this case, there would be a maximum focus distance determined by the limit of the distance the lens can move the focal plane away from the camera and would be a distance less than the hyperfocal distance.

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I think your mean minimum and maximum focus distance, not focal. – Michael Clark Nov 15 '13 at 20:23

Your question makes no sense. The max distance for all normal lenses is infinity. The focal length will only determine the view angle at infinity, not whether you can reach infinity or not.

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It depends on how you define normal. Many Macro lenses are not capable of focusing on infinity. – Michael Clark Nov 15 '13 at 20:24
@Michael: Actually some macro lenses still focus to infinity, like my Nikko 60mm f/2.8. But yes, I'm not considering a specialized macro lens that can only focus close to be "normal" in this context, which I think is obvious enough from what I said. The point is that the minimum and maximum focus distances have nothing to do with focal length. That is a matter of lens construction. – Olin Lathrop Nov 15 '13 at 22:39

Pretty much any lens can focus at infinity, so I think to make sense, the question must mean maximum distance so that the image of subject is a usable size instead of a dot. Which is going to be hard for anyone else to judge, but a Field Of View Calculator should answer for individual purposes.
See http://www.scantips.com/lights/fieldofview.html

The Field Dimensions are the size of the distant area that the camera sees. Enter a focal length and sensor size, and it will tell you field of view size for your distance. Or tell it your desired field size (dimension or angle) and it will tell you distance.

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