I started looking for an UWA lens (something in the mid-teens), particularly for doing milky way shots. Learning that you get trails with too long of exposure, I figured I'd try and find the largest aperture possible. After searching endlessly, I seem to notice a trend that there aren't lenses less than ~24mm, and particularly in the teens, that have f-stops less than 2.8.

Am I crazy? If not, then is there some technical reason as to why? (the f-stop part, not me being crazy)


Edit to mention I'm shooting a Canon 6D.

  • This Sigma 20mm is the closest I could find. bhphotovideo.com/c/product/217794-USA/…
    – kenny
    Jun 26 '13 at 4:47
  • 4
    Full-frame or APS-C? There is a new Sigma 18-35mm/1.8 for APS-C that should be available in EF-S shortly (the Nikon version has just been released). (Getting a sufficiently large image circle with acceptable vignetting at large apertures is one of the major stumbling blocks.)
    – user2719
    Jun 26 '13 at 5:56
  • Yes, Full-frame. Question edited to add that.
    – kenny
    Jun 26 '13 at 13:47
  • Just wondering, if you're taking long exposures, wouldn't you want to close the aperture anyway?
    – BBking
    Oct 20 '13 at 23:58
  • @BBking for milky way photos in particular, you shoot long exposure because you need to gather as much light as possible. Closing the aperture would defeat that purpose. There are trade-offs, though. You can gain some sharpness and reduce abberations even stopping down 1/2 a stop.
    – kenny
    Jan 20 '17 at 16:25

The problem with fast wide angle lenses is that a fast lens by definition has a large entrance pupil, and to illuminate the image plane the entrance pupil has to be visible across the field of view. So a combination of wide aperture and wide field of view is very difficult to achieve. In addition wide angle lenses for digital cameras are often retrofocus design, and aberrations become very hard to control the wider the aperture.

There are 24mm lenses available for the Canon mount that are f/1.4, namely the Canon 24mm f/1.4L (I and II) and the Samyang/Rokinion/Bower (same lens different name) 24mm f/1.4. The latter is probably a better choice than the Canon as it is much cheaper and being manual focus only doesn't really matter for astrophotography.

Sigma make 24mm f/1.8 and 20mm f/1.8 lenses for full frame, as well as an 18-35 f/1.8 zoom for APS-C. If you are shooting APS-C then the widest you can go sub-f/2.8 is with the Samyang/Rokinion/Bower 16mm f/2.0, same as above, manual focus only but should be fine for astrophotography.

  • Since I'm Full-frame, I think I'm correct in assuming that my only true choice of lenses that meet my criteria (sort of) is the Sigma 20mm f/1.8.
    – kenny
    Jun 26 '13 at 13:53

There are quite a few. Even if you filter those , there are currently 6 options for EF-mount. Both Canon and Samyang make a 24mm F/1.4 which have the largest apertures in the group, while Sigma offers a 20mm F/1.8 and 18-35mm F/1.8 which are still very bright but offer a wider field-of-view on APS-C cameras.

  • 2
    +1 for exposing me to neocamera. Great lens search feature!
    – kenny
    Jun 26 '13 at 13:56

Not to be forgotten - Leica 21mm f/1.4, which they position as world fastest wide lens. Not exactly canon, but I thought it's worth mentioning


Yes. If you're wiling to step into the world of cinematography, there are plenty of ultra wide angle lenses faster than f/2.8. If you don't mind carrying a 5 lb lens with manual focus (And you may need to find a PL to EF adapter), then look no further!

Unfortunately, they're $12,000+ a piece and may vignette severely on full frame cameras.


Actually we have from Sigma 20mm F1.8! While Samyang 24mm f/1.4 is another option but remains at 24mm. If you're looking for wider lens then it is the Samyang 14mm f/2.8 but the aperture remains the same. They also have the Samyang 8mm f/3.5 if you want an extremely wide angle lens. All these lenses are for full frame DSLRs. The brand may not be familiar, but it is a prosumer lenses. TV and Movie industries (of course I'm not allowed to name any) use these lenses.

Visit their Website for more info.

Sigma Lenses has also fast wide angle lenses.

  • 9
    I don't see how the 14mm f/2.8 or 8mm f/3.5 are faster than f/2.8.
    – Philip Kendall
    Jun 26 '13 at 7:26
  • 7
    And I don't see why 24<24.
    – asalamon74
    Jun 26 '13 at 12:08

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