What does a lens’s minimum focus distance actually mean if depth of field extends closer?
Asked 8/6/2019
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My lens barrel shows a minimum focus distance (measured from the sensor plane). I understand that this is the closest distance at which the lens can be focused.
What confuses me is depth of field: when the lens is focused near that limit, objects slightly closer can still look acceptably sharp. Older lenses also show depth-of-field and hyperfocal scales that suggest a range of distances can appear in focus.
So what does “minimum focus distance” really mean? Is it the closest exact focus point, while depth of field only gives an acceptable sharpness range rather than true focus?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
6y ago
2 Answers
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Minimum focus distance means minimum focus distance of the lens (unless additional accessories are added). Lenses focus at only ONE precise distance, period. Depth of Field adds to that (plus and minus, as an acceptable zone) only providing an approximate "good enough" sharpness zone as defined by CoC (Circle of Confusion).
Depth of Field numbers of say 2 to 10 feet or meters absolutely does NOT mean 2 to 10 distance is in focus. Any lens can be focused at only one distance. DOF 2 to 10 only means the out of focus blur does not exceed the CoC value until either 2 or 10 distance is reached. "Good Enough" maybe, but not critically sharp focus except at one distance.
Originally by user38978. Source · Licensed CC BY-SA 4.0
user38978
6y ago
0
Generated from our catalog & community — verify before relying on it.
Yes — minimum focus distance means the closest distance at which the lens can be set to exact focus, usually measured from the sensor plane. The lens focuses at only one precise distance at a time.
Depth of field does not mean multiple distances are truly in exact focus. It describes a range in front of and behind the focus point that appears acceptably sharp, based on a circle of confusion standard. So if something slightly closer than the minimum focus distance still looks sharp enough, it is not actually the lens’s exact focus distance — it is just within the acceptable blur range.
That’s why the term “minimum focus distance” is still correct. It refers to the nearest exact focusing position the lens can achieve without accessories such as extension tubes or close-up filters.
Older depth-of-field and hyperfocal scales are consistent with this: they indicate zones of acceptable sharpness, not multiple exact focus distances.
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