How is minimum focus distance measured on Nikon macro lenses?
Asked 11/19/2011
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For Nikon DSLR lenses, when the specs list a minimum focus distance like 18.5cm on the AF-S Micro-Nikkor 60mm, is that distance measured from the camera sensor/focal plane to the subject, or from the front of the lens? Reviews sometimes also mention a much shorter “working distance” from the front of the lens to the subject. For example, how can a lens have a minimum focus distance of 18.5cm but only about 4.8–5cm between the lens front and the subject at closest focus?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
2 Answers
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The answer is here, from Nikon:
Minimum Focus Distance
The minimum focus distance is the shortest distance at which a lens can focus. In the case of digital SLR cameras, the distance to the subject is measured from the focal plane mark on the camera body, not from the front of the lens.
Since the lens has a minimum focus distance of 18.5cm, and is 8.9cm long, and there's a 4.6cm flange to focal plane distance for the Nikon mount, that leaves about 5cm to spare, which is just about what Ken says (especially given that lens length is probably not measured exactly from the mounting flange on the lens).
It's also worth noting that this isn't Nikon specific — all lens minimum focus distances are specified in this way, although terminology may vary slightly. (Sony uses the same term as Nikon. Canon calls it "Closest Focusing Distance", and Pentax uses "Minimum Focusing Distance". Olympus and Panasonic are inconsistent, using "Closest Focusing Distance" in lens specifications but "minimum focusing distance" in articles.)
Originally by user1943. Source · Licensed CC BY-SA 4.0
user1943
14y ago
0
Generated from our catalog & community — verify before relying on it.
On Nikon DSLRs, minimum focus distance is measured from the camera’s focal plane mark (the sensor/film plane) to the subject, not from the front of the lens.
So there’s no contradiction between 18.5cm minimum focus distance and roughly 4.8–5cm in front of the lens:
- 18.5cm = focal plane to subject
- subtract the camera flange-to-sensor distance
- subtract the physical length of the lens
- the remainder is the front-of-lens to subject distance, often called working distance
That’s why a macro lens can have a published minimum focus distance of 18.5cm while the subject appears only a few centimeters from the front element at maximum magnification.
In short:
- minimum focus distance = camera focal plane to subject
- working distance = front of lens to subject
The latter is usually much shorter and is often the more practical number for macro shooting.
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