Why is one lens labeled macro at 17cm while another isn’t at 16cm?
Asked 7/4/2019
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Canon’s RF 35mm f/1.8 is marketed as a macro lens with a 17cm minimum focusing distance, while the EF-S 24mm f/2.8 focuses slightly closer at 16cm but usually isn’t treated as a macro lens. If the 24mm can focus closer, why isn’t it considered macro too? Is this related to sensor size, or is macro classification based on something other than minimum focus distance?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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From Canon's website, emphasis added by me.
The 24mm EF-S f/2.8:
Minimum focusing distance of 0.5 ft./0.16 m; maximum magnification of x0.27.
The RF 35mm F1.8 Macro IS STM:
A 0.5x magnification ratio and a close focusing distance of 0.56 ft./0.17m
Even though the 24mm lens can focus more closely, its wider field of view means that the magnification on the sensor at that closest focusing distance is much less. If you take a macro picture of the same object using both of these lenses as close as possible, you'll find the object fills much less of the (cropped to EF-S) frame with the 24mm lens.
Canon is apparently using the common-these-days threshold of 1:2 as close-enough-to-call-it-macro. The slightly-more-than 1:4 magnification of the 24mm lens doesn't come close enough to merit the label.
Originally by user1943. Source · Licensed CC BY-SA 4.0
user1943
7y ago
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Generated from our catalog & community — verify before relying on it.
Minimum focusing distance alone does not determine whether a lens is considered macro. The key specification is magnification ratio.
From Canon’s specs:
- EF-S 24mm f/2.8 STM: maximum magnification 0.27x
- RF 35mm f/1.8 Macro IS STM: maximum magnification 0.5x
So although the 24mm focuses slightly closer, its wider field of view means the subject appears smaller on the sensor at that distance. The 35mm produces a much larger image of the subject.
Traditionally, “true macro” means 1:1 magnification, where the subject is recorded life-size on the sensor. Many modern lenses marketed as macro reach 1:2 (0.5x), which is likely why Canon labels the RF 35mm as macro. The 24mm at 0.27x is closer to a regular close-focusing lens than a macro lens.
So the difference is not mainly the 16cm vs 17cm distance, and not directly sensor size. It’s the maximum reproduction ratio: how large the subject can be rendered on the sensor.
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