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Wednesday, July 9, 2014

Rokinon 24mm f/1.4 Review

The Rokinon 24mm f/1.4 compared to the Canon EF24mm f/1.4 on the right ($550 vs. $1750)
The Rokinon 24mm f/1.4 ED AS UMC Wide-Angle Lens is hybrid aspherical that is particularly suitable for astro-landscape photography because of its excellent correction for coma aberration, even when used wide open.

Although I have long recommended this and two other lenses made by the Samyang Optics, I have recently received several email messages from prospective buyers, worried about negative reviews they have seen about this lens. This lens is not for general use. It is a totally manual lens —no electronic linkage to the camera, whatsoever. Despite this, it is well suited for astro photography.

Advantages of a f/1.4 Aperture: I have several lenses that I use for astro-landscapes. All but the Rokinon 24mm lens have f/2.8 as their widest aperture. The Rokinon 24mm's f/1.4 provides several nice options.

  • Using f/1.4 allows you to lower your ISO, or...
  • Shorten your exposure time (to reduce star trailing), or...
  • Do both: reduce ISO and shorten your exposure time, or you can...
  • Stop down to f/2.0 to increase sharpness and reduce lens vignetting

A typical exposure with the an ultra wide angle lens is f/2.8 for 25 to 30 seconds @ ISO 6400. With the 24mm f/1.4 you could go f/1.4 @ for 25 to 30 seconds @ ISO 1600. However, because of it's longer focal length, you'll get less star movement by going 13 to 15 seconds @ ISO 3200. And if you've got a good low-noise camera sensor, you won't mind going to ISO 6400 and closing down to f/2.0 for the increase in depth of field (for close foreground objects) and significantly reducing the lens' vignetting (see "My Personal Preferences", below).

Comparison: Let me share a comparison I did with my $1,750 Canon EF24mm f/1.4L II USM and the $550 Rokinon 24mm f/1.4. (The Rokinon is also branded as a Samyang or Bower. They are all the same lens, made by Samyang Optics.) The following test photos were taken about 15 miles away from Salt Lake City, at the Brighton Ski Resort. Being this close to SLC, the skies are still polluted with light from the valley below, but for a 30-minute drive, it still allows one to record the medium to bright stars.

Night Ski above Brighton Ski Resort ~ Taken with the Canon EF24mm f/1.4 @ f/2.8
(This lens must be stopped down to at least f/2.8 in order to correct its coma aberration.)
At f/2.8, the Canon performed slightly better than the Rokinon, but at f/1.4 and f/2.0,
the Rokinon out-performed the Canon in sharpness and coma correction.
The following images are directly from the camera JPEGs with no post-processing correction for white balance, noise, or lens vignetting:

Full-Frame comparisons: The color rendition of the Rokinon is slightly different from the Canon,
but the most significant difference is lens vignetting. For the extra $1,200 you pay for the
Canon lens, you get about one-stop less lens vignetting in the corners. However, this
can easily be corrected in the Adobe Raw Converter software. (Click to enlarge)
Center enlargements @ 100%: Neither lens exhibits coma in the center, but the Canon is slightly
less sharp and has a touch more color fringing (click to enlarge).
Edge enlargements @ 100%: The Rokinon exhibits about 1/2-stop fall-off on the edges, and about
1-stop fall-off in the corners compared to the Canon. Sharpness is about the same.  However,
the big difference is coma. Canon's coma in the edges and corners is so bad, it's off the chart;
whereas the Rokinon exhibits only minor coma aberration, albeit some color fringing.
(Click to enlarge. Note: the "stick" in the sky is a snow marker for snow plows.)
Manual Focus: the Rokinon is manual everything, including focus —which is not a problem, since auto
focus doesn't work in the dark, anyway! As with any lens used for starry night photography, I find it
a good idea to focus on an "infinity" object (i.e. a tree on the horizon, about 200+ feet away) during
the daytime. I use the camera's "live view" function and magnify my image 10X on the LCD
screen. I've marked that position with a green dot on the lens focusing ring (green turns
black under red headlamp light). The red dot is this lens' 50 feet mark.
Angle of view: About half of my NightScapes are taken with a 14mm (114º angle of view), and the other
half with the 24mm's 84º angle of view. You can capture more of the sky with the 14mm, but when
I want to emphasis the beauty and drama of the Milky Way's Central Bulge, the 24mm is a
perfect fit!  ~ Alabama Hills with the 24mm Rokinon, @ f/2.0, 13", ISO 6400.
My personal Preferences: About 80% of my Rokinon 24mm shooting is done at f/2.0. I prefer to stop down for a little extra sharpness, better depth of field for foreground objects, and a significant reduction in lens vignetting (even though this can be corrected in software, you do run the risk of color cross-overs in your corners, which can also be corrected, but it is an extra post-processing hassle that I'll discuss in another blog post, someday). My typical exposure with my Canon 5D Mark III is f2.0, for 13 seconds @ ISO 6400. This short exposure produces extremely sharp and almost perfectly round stars. Even a two second increase to 15 seconds can sometime produce elliptical-shaped stars, and a 20-seconds exposure is almost sure to have some significant star movement. Mind you, this movement is only noticeable in large prints of 20x30 inches or larger —but that's the kind of quality I'm shooting for.

Conclusion: I find the Rokinon 24mm f/1.4 lens offers great performance, especially when one considers the price. The advantage of having an f/1.4 aperture in your arsenal of lenses provides many options that other lenses don't offer.

Pro: Low price. Good sharpness. Excellent coma corrections. Fast, f/1.4 aperture. Good construction. Cons: Significant lens vignetting, but this can be mostly corrected with software. Many non-critical (low-tolerance) components are made of plastic to reduce cost. This does not affect performance, but can affect long-term durability in rough environments and handling. Manual everything: Manual focus, manual aperture, and no electronic coupling to your camera body (no EXIF info can be transmitted to the image file).

The Rokinon 24mm is available through B&H in the Canon mount, Nikon mount, and Sony mount. Note: The Nikon mount includes an electronic focus confirmation and auto aperture chip that adds about $50 to the price.






9 comments:

  1. Royce,
    Back a couple years ago when I compared the two lenses, I also noted that the vignetting appeared worse on the Rok than the Canon on the LCD and in the JPGs. A reader commented that Canon has the ability to apply a lens profile to their own lenses in-camera, but can't do that for 3rd party lenses. When I looked at the RAW files from the two (with no profile applied in LR), the vignetting was similar (as I remember). For the Rokinon, I simply use the Canon 24mm f/1.4 lens profile in LR and it cleans up nicely.
    Best,
    Rick

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    Replies
    1. That works :) Thanks for your feedback, Rick!

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  2. Awesome blog Royce! The best around. Love the advice and an abundance of links too!
    My Sigma 24mm 1.8 EX DG Macro has been giving me some surprisingly sharp results! I stop down to f2.0 and that helps too.
    Recently purchased a used Samyang 14mm f2.8 so am excited to see how that goes next time out. But for me, you can't beat the way the 24mm helps keep the Milky Way large and imposing in the composition! Even if I do have to merge my shots.
    Thanks again and keep up the good work!

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  3. Hi, I have recently purchased a Samyang 24mm f1.4; I see pretty sharp output in the center whereas the corners are pretty bad. Even stopping down to F5.6 for testing; the situation is pretty bad. As you have experience of using these lenses; I want to know if this is what you have faced as well. Or is it a bad copy of the lens that I have received! Thank you very much in advance for your advice.

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    ReplyDelete
  5. Great review and wonderful pictures, Royce. In response to Avisekh's comment, there is horrible quality control done on these lenses at manufacture, so you might have to test two or more copies of this lens to find one that has consistent sharpness across the frame.

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  6. Is this equivilent to the Nikon 24-70mm lens?

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  7. I am new to photography, so sorry if this question is silly. First off your blog is fantastic! I see that you marked the focus ring with a red/green for an aperture at f1.4, however your recommended aperture is f2.0, do you have a separate mark for infinity focus at f2.0?

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  8. This may be a silly question, but what Camera did you test these two lens on if I may ask?

    ReplyDelete