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Canon's 35mm RF f/1.8 STM lens is called a "macro" lens. Its minimum focusing distance is 17 centimeters.

Canon's 24mm EF-S f/2.8 STM lens has a minimum focusing distance of 16 centimeters, less than that of the 35mm RF lens. However, I don't see it usually called a "macro" lens. The 24mm is 38.4mm equivalent, practically the same as 35mm. There is a text "macro 0.16m/0.52ft" written on the 24mm lens, but then again the 40mm EF f/2.8 STM also has "macro 0.3m / 0.98 ft", and it's not called a "macro" lens despite this text.

Why is the 35mm lens a macro lens whereas the 24mm lens isn't?

Is this illogicality:

  • 17 cm EF -> macro
  • 16 cm EF-S -> not macro

related to sensor size, so that different minimum focusing distances are considered macro depending on the sensor size?

Or is there some property other than the minimum focus distance in the lenses, which I'm not seeing? Such as sharpness at minimum focusing distance?

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    \$\begingroup\$ Possible duplicate of What is a macro lens? \$\endgroup\$
    – Philip Kendall ♦
    Jul 4, 2019 at 10:05
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    \$\begingroup\$ I'm not sure whether to click the "That solved my problem." button. The proposed duplicate says "Other properties of macro lenses include that they have fixed focal lengths, usually very low distortion" and it also says "Mostly due to marketing reasons, term macro is now used for lenses with 1:2 or even lower magnification". Is the reason for the difference magnification or distortion? \$\endgroup\$
    – juhist
    Jul 4, 2019 at 10:23
  • \$\begingroup\$ I think the most important point is "macro is just a marketing term". \$\endgroup\$
    – Philip Kendall ♦
    Jul 4, 2019 at 10:40

3 Answers 3

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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.

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  • \$\begingroup\$ Well, one of the lens is EF-S (crop) and the other RF (full frame) so they should fill about the same percentage of the frame... But I guess this is the answer, thanks! \$\endgroup\$
    – juhist
    Jul 4, 2019 at 12:56
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    \$\begingroup\$ @juhist crop factor, or filling percentage of frame, has nothing to do with magnification. The magnification is just the ratio of size on sensor to size in the plane of focus. A real-world 5 mm object in focus that covers 10 mm of pixels has a 2:1 magnification. A 50 mm object further away that covers 10 mm of pixels when in focus has a 1:5 magnification. It doesn't matter if the lens can cover a 1" sensor, Micro Four Thirds, APS-C, full frame, or even large format film. \$\endgroup\$
    – scottbb ♦
    Jul 4, 2019 at 13:17
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    \$\begingroup\$ @scottbb I'm the one who mentioned filling the frame, and crop factor is relevant in this sense. Of course it takes less magnification to fill a smaller frame. \$\endgroup\$
    – mattdm
    Jul 4, 2019 at 13:18
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    \$\begingroup\$ True. My concern is merely that crop factor and frame-fill aren't central to the concept of magnification. They are things to consider with regards to composition, and certainly factor in when talking about final magnification of a print. But the MFD and magnification of a lens is completely independent of the size of the sensor the lens is projecting onto. \$\endgroup\$
    – scottbb ♦
    Jul 4, 2019 at 13:39
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The original definition of "macro" is that the image on film is at least as large as the object in reality. With the amount of small sensor cameras around, that definition is of dubious usefulness. More relevant would be "effective" macro where the imaged area is not larger than 24mm×36mm, the imaging area of a 35mm analog (or digital "full frame" camera), never mind the actual sensor size. I am not sure but I don't think that definition is actually being used.

Instead, "macro" is used for a closeup range of zoom lenses (in compacts or ILC) where potential object magnification is maximised on the wide end of a zoom lens due to minimum focusing distance shrinking more than the viewing angle grows when zooming out. This closeup mode comes at the cost of extreme perspective distortion (sometimes wanted for emphasizing an object in a miniature depiction of its environment) and a very close focusing distance that often causes trouble with lens shadow.

Screw-on closeup lenses or diopters (achromatic for best quality) can be used to shift the maximum magnification from the wide end back to the tele end of a zoom lens, making for more relaxed perspective, positioning, and lighting conditions.

Actually dedicated macro lenses don't get their magnification by rearranging the optical recipe of a normal zoom lens at the wide end for foreshortening the minimum focusing distance: their optical recipe does not prioritize best imaging quality at distances close to +∞ like that of a typical zoom lens and they don't have the typically large minimum focusing distances at their long focal lengths that "normal" zoom lenses have.

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The closest focusing distance is 48cm for Canon's 180mm macro, and 30cm for the 100mm macro, both of which are 1:1 macros, and 24cm for the 65mm 1-5x macro, so it's not the distance that counts.

What makes a macro is its magnification. The subject size is 1:1 on the sensor for a full macro, or 1:2 for many budget macros, as the subject is considered "magnified enough" to warrant the (marketing) term; the 0.5x magnification is much bigger than normal non-macro lenses in general...

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    \$\begingroup\$ and 13cm for the EF-S 35mm Macro \$\endgroup\$
    – xenoid
    Jul 4, 2019 at 17:11

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