Last day I shot using an 18-135mm Nikon lens, it was barely able to capture a fly-sized point at a distance of 100m with proper details. Using a 100-400mm lens would be too expensive. Can you guys suggest a less expensive solution for capturing a 1meter x 1meter square board at 100 meter distance with full view (full screen size image), so that once the image is captured it can easily be analysed to find small dots of the size of a fly.

Zooming and Capturing need to be done from software control or with Python or Java api access.

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    \$\begingroup\$ Google "digiscoping" - basically attach your camera to a telescope. \$\endgroup\$ Commented Mar 28, 2017 at 11:29
  • \$\begingroup\$ Do you need to zoom (and focus) or is your target actually fixed at 100m? What are "proper details"? \$\endgroup\$
    – mattdm
    Commented Mar 28, 2017 at 22:40

2 Answers 2


If your field of view is 1m vertically at 100m, that corresponds to about 1 degree, which corresponds to a focal length of more than 1200mm on a full-frame sensor or 800mm on an APS-C sensor. If you want a cheap lens with that kind of focal length then you should look at mirror lenses (aka reflex lenses), possibly also with a teleconverter. You're also going to want a solid tripod and a remote trigger of some kind. And you're going to have to be quite careful with dust, because automated analyses might interpret dust on the sensor as dots on the target.


Given enough light, a relatively cheap superzoom point-and-shoot may work well enough and cost less than what it would take to make a DSLR work (let's hope you didn't buy your DSLR just for that).

  • \$\begingroup\$ Like what model? \$\endgroup\$
    – Rafael
    Commented Mar 28, 2017 at 19:47

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