Looking for a recommendation for a ultra-wide angle lens

[ChrisPBacon]

I’m looking for and would sincerely appreciate your recommendations for the best prime EF-mount ultra wide-angle lens for use on Canon EOS crop-sensor (7D) and full-frame cameras (specifically 6D, and 6D Mk. II) for astrophotography.

(While there are excellent zoom lenses available, the possible risk of chromatic aberration makes them impractical.  That said, I’m a relative novice to astrophotography and still have a great deal to learn — so if you use a zoom lense for astrophotography, please let me know of your experience.)

I’m imaging asterisms and the Milky Way which require relatively longer exposures but I wish to avoid having stars appear oblong in shape from too-long an exposure; to that end, I need the fastest glass possible to obtain as much detail a lens is capable of capturing — as well as the quality of the detail that is captured. Canon’s 14mm f/2.8L is a good lens, but is it the best quality glass (assuming that cost is not a factor) on the market?  It must be heresy to ask if other manufacturers produce a better lens, but I’m willing to consider all contenders as long as the lens is compatible with my Canon cameras: price is not a consideration.

As I disable autofocus and image stabilization in taking these types of photos, a manual focus (only) lens such as those made by Zeiss is perfectly acceptable.

I’m well aware that below f/2.8, price increases dramatically: while having an equatorial mount would allow for longer exposure times without star distortion, it would create problems for foreground terrain blurring and additional post-production labor, which I’d like to avoid if possible. My 6D is heavily modified for heat reduction and has had its IR filter removed so that light in wavelengths of 656.28 nm appear in photos, but the scale of these structures make use of a telescope impractical.  Light pollution poses another difficulty with increased exposure times, so high-quality fast glass is a better option for my purposes.

Any lens f/2.0 or below, in the range of 8-18mm, might be ideal.  I would appreciate anyone with experience with this lens type sharing their recommendation.

[CaliforniaDream]

I don't know the importance of lens speed but the  Canon 50mm f/1.0 L USM is probably the fastest available.  I don't have one but the reviews make it look like it's IQ is fantastic at f 1.

[ChrisPBacon]

Unfortunately, a 50mm lens isn’t an ultra wide-angle lens: to use it, I’d have to take dozens of photos and “stitch them together” digitally to form the same photo from a wide angle lens. In other words, I’d spend hours doing post-production work in order to save a few seconds — or minutes — of shooting.

it does sound like a great lens, but it wouldn’t be very practical.

[ebiggs1]

OK here ya go.......

For FF cameras

Sigma 14mm f/1.8 DG HSM Art Lens

Rokinon SP 14mm f/2.4 Lens for Canon EF

For croppers

Rokinon 10mm f/2.8 ED AS NCS CS Lens

Sigma 18-35mm f/1.8 DC HSM Art Lens

I might mention the Tokina AT-X 16-28mm f/2.8 Pro FX Lens for Canon.  Not quite as good as the others but very good and at a very attractive price. I have not used the Canon EF 16-35mm f/2.8L III USM Lens. But I own the number 2 version and can't recommend it. The EF 11-24mm F4L USM is extremely good but it is nearly three grand. If ya got the coin I would check it out.  Its a great lens.

But the best lens hands down right now has to be the Sigma 14mm f/1.8 DG HSM Art Lens for Canon EF

[ChrisPBacon]

Thanks for your response.

I’m a bit leery of using a zoom lens due to chromatic aberration inherent in many zoom lenses, and correcting it requires additional post-production software manipulation of the image, which can correct some — but not all — distortions without hours spent in time-consuming, painstaking work.  Even with digital manipulation, stars at the margins of the photo show aberration effects which reduces the useable field of the photo, again requiring multiple exposures which must first be corrected then spliced together, i.e., more time required in post-production in order to get a photo which a prime wide-angle lens can produce. 

The Sigma lens looks promising: anyone else have experience with this lens?  I’ll check it out.  Again, thank you for the suggestion.

[RobertTheFat]

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@ChrisPBacon wrote:

Thanks for your response.

I’m a bit leery of using a zoom lens due to chromatic aberration inherent in many zoom lenses, and correcting it requires additional post-production software manipulation of the image, which can correct some — but not all — distortions without hours spent in time-consuming, painstaking work.  Even with digital manipulation, stars at the margins of the photo show aberration effects which reduces the useable field of the photo, again requiring multiple exposures which must first be corrected then spliced together, i.e., more time required in post-production in order to get a photo which a prime wide-angle lens can produce. 

The Sigma lens looks promising: anyone else have experience with this lens?  I’ll check it out.  Again, thank you for the suggestion.

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Quite frankly, I think you've defined conditions that can't be met with today's equipment. Since i don't do astrophotography, I guess I don't have a dog in this hunt. But you've provoked my curiosity; so if you do find what you're looking for, I hope you'll post the details.

[ebiggs1]

"Quite frankly, I think you've defined conditions that can't be met with today's equipment."

Mr. Bob beat me to the punch. Welcome to the real world.  A lens that is great center to edge only exists at Hogwarts School of Witchcraft and Wizardry.

"...correcting it requires additional post-production 'and' software manipulation of the image..."

This is how great sky photographs are made.

[ebiggs1]

This lens is about as good as it gets, the Rokinon SP 14mm f/2.4 Lens for Canon EF.

[ebiggs1]

BTW, for sky photography you probably don't want the Canon 50mm f/1.0 L USM.  Even if you can find one (they haven't been made for 20+ years) and if you do a pristine copy can hit $7000, average around five grand. They are legendary and wonderful and fantastic, I wish I owned one but not for the sky. They have that same awkward focus like the EF 85mm f1.2L has.  Not the best but it works.  

[TCampbell]

Keep in mind that as the aperture gets larger, you are far more likely to notice things like coma.  Stopping down even a tiny bit usually helps in a very noticeable way.  

The Rokinon/Samyang lenses are popular and, if you get a good copy, pretty good optically.  They have a bit of a quality control issue where it's not uncommon to get a copy with de-centered optics (e.g. if you pointed your camera at a flat brick wall so the camera sensor is perfectly parallel to the walll, you would notice the optimum focus isn't actually in the very center of the frame.  While focus fields are usually not perfectly flat (there's a bit of a curvature in depth of field, so it's common to have corners that aren't quite as sharp as the center) if the optics are de-centered, the focus would be noticely weaker on one side of the frame than the opposite side of the frame (normally you'd expect the focus to degrade symmetrically as the distance from center axis increases.)

You can massivly increase exposure time if you have a tracking head.  The normal "sidereal" rate for tracking ("sidereal" is the speed at which the Earth rotates on it's axis ... one completely rotation in about 23 hours 56 minutes and a few seconds) is roughly 15 arc-seconds per second.  As the Earth spins West-to-East, the tracking head spins East-to-West at the same rate ... and as long as the tracking head's rotating axis is parallel to Earth's axis, they cancel each other out.  You can take very long exposures if needed (the ground will blur).

They do feature a half-sidereal speed ... splitting the difference between when the ground has moved enough to blur vs. when the stars have moved enough to blur.  

Suppose you use the "500 Rule" with a full-frame camera like your 6D and suppose you have a 20mm lens (I'm justing using that as an example).  500 ÷ 20 = 25 (you can take a 25 second expoure).  Using a tracking head at half-sidereal speed you can exposure for 50 seconds.  If you used a 14mm lens (about 35 seconds) you could shoot for 70 seconds.

The popular vendors for these heads are iOptron (Sky Guider Pro head) and Sky Watcher (Star Adventurer head) - both are priced competively and seem to be roughly similar in quality.