What are difference between canon 50 mm f/1.8 STM vs canon 50 mm f/1.8 II ? which is better to buy?


2 Answers 2


Go to The-digital-Picture.com, search for Canon 50mm f1.8 STM review, click on "Image Quality". This web page will let you see the images of a resolution chart as taken with the selected lens. You can choose what camera body, the focal length (if it's a zoom lens), the f-stop, and a different image will be shown. You can choose another lens on the right side to compare. In this case you can choose the Canon 50mm f1.8 II. Move your mouse pointer on top of the little arrow at the top of the image and it will switch to the image taken by the second lens. Move the mouse away, it will show the first image. I find this lens comparison site very useful.

From the sites comparison between the 2 50mm lens, the STM lens produces slightly better results from f1.8 up to f8 (especially the mid-frame part of the images), when both lenses become equal. So I think they may not be optically the same.


  • \$\begingroup\$ Canon's Chuck Westfall has already commented that the optics are the same. The difference that Bryan at TDP is showing is almost certainly sample variation - the build quality on the previous generation wasn't very good. \$\endgroup\$
    – crunch
    Commented Jul 10, 2015 at 6:47

The STM version replaces the II version. Optically, they are identical. However, the STM has several advantages:

  • 7 rounded aperture blades vs. 5 non-rounded (no more pentagonal bokeh)
  • Metal lens mount vs. plastic
  • A much improved manual focus ring
  • STM vs. Micro Motor (should be faster and much quieter)
  • FTM (Full Time Manual) focusing
  • 13.8" (350mm) MFD (Minimum Focus Distance) vs. 17.7" (450mm)
  • 0.21x MM (Maximum Magnification) vs. 0.15x
  • 49mm vs. 52mm filter size (though not really an advantage from my perspective)
  • Narrower f/22 aperture available vs. f/16

All that for the same price! To answer your question: get the STM version.

  • 1
    \$\begingroup\$ Note that while in this particular comparison the STM version is both quieter and slightly faster: In most cases when comparing comparable non-STM and STM lenses the non-STM lens will usually be faster to focus and the STM lens will be quieter. This is especially the case if the non-STM kens has an UltraSonic Motor (USM) (and most Canon lenses other than the cheapest consumer grade lenses use USMs). \$\endgroup\$
    – Michael C
    Commented Jul 3, 2015 at 13:51
  • \$\begingroup\$ If you compare STM versions of lenses that existed previously as non-STM lenses, then the STM lenses are both faster and quieter: 18-55, 18-135, and 55-250. There are no Canon lenses with USM and STM versions so that's comparing apples to oranges. \$\endgroup\$
    – crunch
    Commented Jul 3, 2015 at 15:01
  • \$\begingroup\$ EF 24mm f/2.8 IS USM vs. EF-S 24mm f/2.8? \$\endgroup\$
    – Michael C
    Commented Jul 3, 2015 at 15:51
  • \$\begingroup\$ Not to mention "comparable" doesn't have to mean a direct replacement. The EF-S 17-55mm f/2.8 IS USM is a lens often compared to the various versions of the EF-S 18-55mm kit lenses. \$\endgroup\$
    – Michael C
    Commented Jul 3, 2015 at 15:55
  • \$\begingroup\$ USM lenses in the same focal length and aperture range are uniformly faster focusing than STM lenses in the same focal length and aperture range. But they are not quieter. \$\endgroup\$
    – Michael C
    Commented Jul 3, 2015 at 15:57

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