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I have a D7200 which I want to use at long distances in low light photography. The kit lens, a 18-140 does not have focus markers on it. Furthermore, the focus ring does not stop hard at any point.

Short of trial and error, or a fixture to assist, how do I focus at infinity for my night shots. Assume that there is insufficient ambient light for live view or viewfinder focus, so the answers to How can I find infinity focus on a kit lens with no markers? do not generally apply.

In my instance, my exposures are in minutes.

This question might apply to other unmarkled focus rings on similar kit lenses. And on other Nikon bodies.

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  • \$\begingroup\$ Related; How to nail focus for DSLR astrophotography? and How do I focus in low light for long exposures? \$\endgroup\$
    – Michael C
    Commented Sep 17, 2019 at 22:01
  • \$\begingroup\$ There are at least a half dozen viable schemes for precise focus setting, but in this instance, i am looking for the equivalent of the infinity marker on a lens, which doesn't have a observable focus ring. \$\endgroup\$
    – mongo
    Commented Sep 18, 2019 at 12:56
  • \$\begingroup\$ Additionally, astrophotography is not the only low light level photography application where infinity focusing is needed. Landscapes, such as mountain ridges are another example. Furthermore, while not a precise focus, one can stop down the lens to enhance the DoF, and while not getting a precise sharp focus, it may be acceptable for many applications. Besides, the HVS acuity is so low at low light levels, that almost anything looks like an improvement over the eyeball at night...except for single photon detection, where the eyeball still wins. \$\endgroup\$
    – mongo
    Commented Sep 18, 2019 at 13:07
  • \$\begingroup\$ In my experience almost all of the non-astrophotography applications that involve low light and longer focus distances also include point sources of light, unless you are shooting in the Sahara Desert. We humans love to put lights everywhere we go. \$\endgroup\$
    – Michael C
    Commented Sep 18, 2019 at 20:39
  • \$\begingroup\$ @MichaelC that experience has apparently missed a plethora of opportunities, including sunsets, where there is seldom identifiable points of light, unless every pixel is considered a point of light. \$\endgroup\$
    – mongo
    Commented Sep 19, 2019 at 10:53

2 Answers 2

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What I've done with the 7200 is:

Set the "OK" button to 100 percent zoom. If you can see your target in Live View then refine your focus live.

If you are taking a longer exposure and cannot resolve your target in live view, test shoot and again use the "OK" button to jump to 100 percent zoom to refine your focus.

Note that there are two settings, one for Live View, and one for Playback.

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With the lens on the camera, rotate the focus ring counter-clockwise until it hits one of the soft detents. That should be the infinity focus point.

(Source: Nikon Customer Support. I found many people asking this question on various forums, so I thought posting the answer where it could be found would help.)

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    \$\begingroup\$ That will get you close, but probably not precisely enough for point sources of light such as stars. \$\endgroup\$
    – Michael C
    Commented Sep 17, 2019 at 22:02
  • \$\begingroup\$ Well, yes and no. It will be close, but I don't have a f/1 lens, so there is some DoF. Again that is not absolutely precise, so there are other techniques. In my instance I was looking for the equivalent of setting the focus mark to infinity. \$\endgroup\$
    – mongo
    Commented Sep 18, 2019 at 12:54

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