Looking for a value-priced ultra-wide angle lens with a wide aperture that delivers sharp images across even a full frame sensor? You may have found your lens – as long as only the most basic lens features are adequate for you. This is a manual focus, manual aperture, manual exposure lens that does not report any information (not even the aperture used) to the camera. However, the feature that matters most for most ultra-wide angle photography, image sharpness, is there and the very affordable price makes this lens a very attractive option.
Samyang used to make their lenses available in a variety of brands, but market demand led to only the top-selling Samyang and Rokinon-brand lenses remaining in its product lineup. Note that chipped versions of this lens are available, supporting some additional features including autoexposure and focus confirmation, at a higher price (sometimes substantially higher).
I like to start lens reviews with a look at the focal length. Focal length matters because it drives focus distance choices and perspective is then determined. And, when you can't back up any further, 14mm might be the right choice.
While this lens' 115.7° angle of view is not going to be confused with a fisheye lens' angle of view, it is one of the widest rectilinear (vs. fisheye) focal length options available. Very wide angle focal lengths can capture the big scene in one frame and, especially with today's high resolution cameras, can provide a panorama look by simply cropping the top and bottom from a single, uncomplicated image capture. More so, wide angles are about making foreground subjects large in relation to background subjects and about including a lot of that background in the frame.
This angle of view is notably able to give the viewer a sense of the presence in the images captured by it. Do you feel like you are standing in this grain field?
While a 14mm focal length is a basic need in an APS-C (1.5x/1.6x FOVCF) kit with many lenses available to cover this angle of view, it is a less-used full frame focal length. However, it is an important one.
Subjects you will want to have a 14mm angle of view on hand for include landscapes (especially), nightscapes, cityscapes, architecture (both exterior and interior), real estate, etc. If photographing these subjects is on my to-do list, this focal length is very frequently part of my kit. I know, I view most lenses as being useful for landscape purposes (and, most really are), but landscapes are right at the top of the 14mm uses list. After verifying the image quality was up to my requirements, I made this lens one of my primaries for a short trip to Island Beach State Park.
Try using this lens for looking-up photos in the forest. Lay on your back amidst interesting tall trees for an easy-to-capture composition that, with each tree trunk becoming a leading line into your frame, looks great.
The night sky is vast and full of interest (and the daytime sky often is as well). The 14mm angle of view can take in much of the sky.
The 14mm focal length can, especially with the interesting perspective it provides, capture artistic types of imagery.
Like most other focal lengths, 14mm can be used for portraits. Just don't get too close.
It can make one's nose look big and, unless your subject has a good sense of humor, they will not likely appreciate this look. Because of this perspective issue, 14mm is usually not a great choice for people framed tighter than very loosely-framed full bodies. Also, keep people away from the edges of an ultra-wide angle frame as they may appear warped. However, environmental photos of individuals and groups captured at a wide range of locations, from scenic landscapes to birthday parties in small rooms, are a good use of a 14mm lens and a good reason to have such a lens in your kit.
As mentioned being an ultra-wide angle strength is emphasizing subject size via perspective. The 14mm angle of view is great for this. While this attribute may not be kind to the dog's nose, it can be quite valuable in other situations. Show a beautiful foreground subject (such as a flower) in front of an interesting background (such as a mountain range). Emphasize a product, or make part of a product stand out. Want to make your small fish into trophies? Simply hold them out toward and close to the camera with a 14mm lens mounted. Your guppy will become a whale (to back up your fish tale), though the beautiful lake and mountains in the background may give away your fishing hot spot.
Considerations must be made when using a 14mm focal length with flash. First, with this lens not reporting to the camera, the flash is not going to know what focal length to auto set to. However, since 14mm is wider than most flashes natively cover, it will not matter. A diffuser (either built in or accessory) or bounce flash (or similar) will be required to avoid an only partially lit scene.
To see how 14mm fits into the neighboring focal lengths, I'll borrow a comparison example from the Canon EF 11-24mm f/4L USM Lens review.
As mentioned, there are many APS-C lenses covering the 14mm focal length. However, few of them have an f/2.8 aperture available. Thus, even APS-C format camera owners may find this lens interesting. On this format, the 14mm focal length provides an angle of view similar to a 22.4mm lens on a full frame sensor format body. The 22mm AOV (Angle of View) is just wider than the ultra-popular and very useful 24mm focal length (shown above) and useful for similar purposes.
The list of uses for 22mm is very similar to the 14mm list, but with the narrower angle of view, the uses shift away from dramatic perspectives and ultra-grand landscapes toward an often easier to manage field of view that will still create compelling compositions. The 22mm focal length framing equivalent will especially be kinder to people and will make keeping groups of people similarly sized an easier task.
As of the Samyang 14mm f/2.8 IF ED UMC Lens review time, there is no alternative 14mm lens with a wider aperture and there is not even a full frame lens wider than 20mm with an aperture opening exceeding this one. Looking at apertures overall, f/2.8 is considered "fast", but keeping perspective, it is two stops slower than the f/1.4 aperture commonly found in fast prime lenses. Still, this is as good as it gets below 20mm. Update: The Venus Optics Laowa 12mm f/2.8 Zero-D Lens has since become available.
An f/2.8 aperture is good for stopping motion in low light. The rate at which subject matter is moving across imaging sensor pixels determines the shutter speed required to stop motion. When using a wide angle focal length, subjects tend to be smaller in the frame (especially background subjects) and their motion is slower to cross pixels.
So, stopping action in low light may not seem to be a need for a 14mm lens. Still, this is an important capability. For example, when photographing the night sky, the rotation of the earth creates star trails in long exposures. A wide aperture permits a shutter speed short enough to be used at an acceptably noisy ISO setting.
Have people in your frame? Even at 14mm, their movement can create motion blur if a too-long exposure is used. Flora blows in the wind; fauna is seldom still. As long as the depth of field is adequate, f/2.8 stops the blur without ultra-high ISO settings being resorted to.
As mentioned in the beginning of this review, this is a manual aperture lens. While the camera's autoexposure system can still be used, the aperture is *always* manually set via an aperture ring located near the lens mount. The camera's Tv mode will work the same as full manual mode. You can change the shutter speed, but the aperture ring will also have to be manually turned to affect the final exposure. Note that the lens will not report the selected aperture to the camera and the aperture setting will not be recorded in the captured image's EXIF information.
While the camera's autoexposure can be used, I found it to be inaccurate at stopped down apertures (overexposing). When performing lens tests, I am frequently stepping through the available apertures to identify image quality changes. Using Av mode (I pick the aperture and the camera selects the shutter speed) often makes this process easy, but not in this case. The site's standard vignetting results are captured utilizing Av mode. The brightness difference showing at f/8 is especially obvious. Note that chipped versions of this lens (in one of the brands) are available and address this issue, but they are priced higher.
My Samyang 14 experience has been much better using manual exposures, though +/- exposure compensation can be successfully used if a narrow range of apertures are being used. Keep in mind that using manual exposure mode can be challenging if shooting under rapidly changing light conditions.
The aperture adjustment is easy (simply turn the aperture ring), but you need to know that click stops are in 1/2 stop increments. If you are used to making 1/3 stop adjustments in-camera (often the default), care must be taken to match manual exposure adjustments (shutter speed and ISO) to those made on the lens. More than once I adjusted three clicks on the camera and three clicks with the ring.
Note that there is one exception to the half stop aperture settings – the half stop between f/2.8 and f/4 is not available. Not available unless you stop the ring in between the click stops. While this can be done, the "cine" version of this lens, with its de-clicked aperture, may make more sense for your needs if you foresee doing this frequently.
Depth of field preview is always enabled when using this lens. With a manual aperture implemented on the lens, the view through the lens is always stopped down (unless using f/2.8 of course). While seeing the actual depth of field at the selected aperture can be advantageous, a sure downside is the darkened viewfinder provided at narrow aperture settings. At f/2.8, the viewfinder is bright. By f/5.6, there is noticeable darkening and it only gets worse as the lens is stopped down further. I like to compose (for the brighter viewfinder) and focus (better precision with a shallower DOF) with the aperture set to f/2.8, then adjust the aperture as desired prior to photographing.
While the f/2.8 aperture is a strong component of creating a diffuse background blur, reality is that the ultra-wide angle focal length is not. The background details are not much enlarged and generally remain identifiable in 14mm images.
The above image was captured at f/2.8 at near minimum focus distance for this lens. It is not hard to identify the background in this image. Same with the dog nose image shown further above.
Another very important parameter for lens selection is image sharpness, the term commonly used to describe contrast and resolution. It is a rare time when I have preferred softer over sharper, and in those few instances, I could usually use an aperture narrow enough to show some diffraction to achieve softer. However, there have been many more times when I preferred to have sharper over what I was working with at the time. The good news is that this lens delivers nicely in the sharpness factor.
The Samyang 14 is quite sharp in the center at f/2.8 and has very usable sharpness across the entire full frame sensor image circle at this wide open aperture. The full frame corners are just slightly soft, but they are quite good, especially for a lens this wide. If sagittal lines (like spokes on a bike wheel) and meridional lines (perpendicular to sagittal) were equally sharp, the corner results would be especially impressive.
Stopping down to f/4 results in a slight increase in sharpness in the center of the frame with results rendered razor sharp. Very little center of the frame difference is seen by stopping down further and none is needed.
To generalize, image sharpness improvements made by stopping down are not as abrupt in the periphery of the image circle. The decent f/2.8 results transition to great by f/5.6 with only the extreme full frame corners showing a very slight softness by f/8. Some corners of my lens are looking fantastic at f/5.6.
Overall, the sharpness of this lens is quite impressive for its price.
Let's look at some real world examples, starting with a set taken from this lens' best-performing location near the center of the frame. These images (and those following) were captured with a Canon EOS 5Ds R in RAW format and processed in DPP using the Standard Picture Style with sharpness set to "1" and cropped to 100% resolution.
I often use a weeping Norway spruce tree as a subject for evaluating sharpness for many reasons including that it does not move in a light breeze, has sharp needles and has enough depth to insure examples can be taken from the center of the depth of field. In this example, the f/2.8 aperture is looking excellent in this area of the frame, appearing nearly as sharp as f/4 where this lens really delivers impressively. It makes little sense to stop down to f/5.6 aside from gaining increased depth of field (which is of course important sometimes).
I'll next share a pair of extreme full frame corner comparisons, starting with one of this lens' impressive corners, the bottom right. Note that to get the corners bright enough for image quality evaluation at f/2.8, these images are, overall, quite overexposed.
There are few wide angle lenses available that can improve upon these corner results. Though dark at f/2.8, the needles are sharp.
Even though the extreme bottom left corner results shown below are not quite as impressive as the bottom right results, they are still quite good.
I am most interested in corner sharpness when photographing landscapes. When photographing landscapes with sharp corners desired, I am usually using f/8 or f/11. At these apertures, this lens performs superbly across the entire frame.
Yes, this lens has an f/2.8 aperture, but with approximately 5 stops of vignetting in the corners, the entire frame is not benefiting from this feature. While this lens ranks among the strongest vignetting lenses available, it is not much worse than the Zeiss 15mm f/2.8 with 4.5 stop. The Nikon 14mm f/2.8 has 4 stops and the Canon 14mm f/2.8L II has about 3.5 stops of peripheral shading at this aperture. That the Samyang's shading gradient is so gradual, with darkening happening evenly from the center to the periphery, this lens' shading is not as obvious as one might expect. The shading can be beneficial in some images, drawing the viewer's eye to a more-centered subject.
Prefer your corners more evenly bright? Correcting 4 or 5 stops of shading is going to result in noisy image corners. Stopping down is always an option, as long as the other attributes of the narrower aperture are acceptable. At f/4, this lens has about 3 stops of shading remaining and a just-noticeable 1.5 stops remains at f/5.6. Shading continues to decrease until roughly 1 stop remains from f/8 through f/16. This amount is still slightly visible in some images.
APS-C format sensor cameras will see about 1.5 stops of shading in f/2.8 corners. With shading falling under 1 stop at f/4, stopped-down images captured with these cameras will have no noticeable shading issues in most scenarios.
The Samyang 14mm f/2.8 Lens takes control of CA (Chromatic Aberration). I seldom see significant lateral (or transverse) CA even in full frame corners. Here is a 100% crop for the near-extreme top left corner from an EOS 5Ds R image:
Only a very small amount of LatCA-caused colors is seen along the edges of the high contrast shadow-to-sunlight transitions (meridional lines).
Color fringing is practically nonexistent.
That big, beautiful convex front element is both eye-catching and light-catching. When bright lights are in the frame, this lens will show a moderate amount of flare relatively easily and with this ultra-wide angle of view, it is not hard to get bright lights, especially the sun, into the frame. Try to block most of the sun with a subject or ... simply embrace the flare.
Coma is generally recognized by sharp detail contrast towards the center of an image and long, soft contrast transition toward the image periphery. Coma is most visible in wide aperture corners and significantly resolves when the lens is stopped down. Pin-point stars in the night sky are the subject that brings this aberration out most easily for me and, with this lens' focal length and aperture being great for night sky photography, I was anxious to focus it on the stars.
The image above is a 100% crop from the top right corner of a 30-second-exposed 5Ds R-captured image. While the stars are not perfectly round (and include small amounts of star trails), this is one of the better-performing lenses available in this regard.
If you asked me what this lens' biggest optical weakness is, linear distortion would be my answer. If there is a straight line in the frame, it will not likely be straight in an image (unless it runs directly through the center of the frame). The mustache distortion, appearing as a bulge in the middle of the frame, is rather strong. APS-C sensor format cameras are not exempted from this issue and a strong barrel distortion should be expected in such images. We are not talking about fisheye-level barrel distortion, but ... enough distortion to warrant correcting in some scenarios.
Geometric distortion makes framing a scene with a straight horizon, such as the ocean, challenging as there are no lines parallel to the edges of the viewfinder or viewfinder gridlines. Cameras with electronic levels have a big advantage in overcoming this issue.
Although many detailed scenes will hide the Samyang 14's distortion, you will often want to correct it in post processing. Those using Canon or Nikon's software will need to look elsewhere to accomplish this task. A favorite option is PTLens, though the standalone version of this tool accepts and outputs only JPG files, assuring at least a second generation of compression data loss on top of the always-destructive process of correcting the distortion. The PTLens plugin for Photoshop is a better option from a file format perspective.
For those standardized on the Adobe image editing platform (Photoshop and Lightroom), Adobe Lens Profile Creator or Downloader can be used (requires Adobe AIR to install) to download the proper lens profile.
In comparing these two correction options, I found the PTLens correction to slightly under-correct and found the Adobe lens profile I downloaded to slightly overcorrect the distortion by default, though the distortion correction percentage can be adjusted in ACR (Adobe Camera Raw).
DxO Optis Pro reportedly does a nice job correcting this lens' distortion.
I know that the earth is round and that 14mm is an extremely wide angle focal length, but that is not the curvature of the earth you are seeing here:
Adobe Photoshop was used for this correction.
Videographers will be more-challenged by this lens' linear distortion pattern.
Bokeh, referring to the background blur quality, is not a strong asset of this lens, but ... a strong background blur is also not easy to create with a 14mm lens.
The 6-blade aperture creates hexagonal shapes from out of focus points of light and those shapes are not evenly filled, having a rough appearance.
Overall, from an image quality standpoint, the Samyang 14mm f/2.8 Lens scores big points in the image sharpness and CA categories, but takes an especially big hit in the distortion category. Considering the price of this lens, many will be able to overlook the latter.
As already noted, this is a manual focusing lens – autofocus is not available. While MF-only simplifies a lens from a design and construction (and testing) standpoints, it limits the lens' usefulness for some and for certain applications. Most will find wider angle MF-only lenses easier to use for focal length-appropriate purposes than telephoto options as the generally-deep DOF allows more room for error. Still, I struggle manually focusing this lens at f/2.8 at close distances using a viewfinder lacking MF aids (primarily, a split prism).
While the Nikon version of the Samyang 14mm f/2.8 lens includes a focus confirmation chip (and costs a bit more), the Canon version does not offer that feature. The Rokinon-branded 14mm f/2.8 lens is offered in a version that "... supports focus confirmation, auto exposure, auto metering and auto white balance functions." The price differential for this version of the lens is significant. I do not find DSLR focus confirmation lights to be accurate enough during manual focusing to count on, but ... some versions of this lens have this option.
Fully zoomed Live View manual focusing or the equivalent (such as using a tethered laptop) is the ideal way to focus this lens.
Of primary importance in a MF-only lens is the manual focus ring. The Samyang 14mm f/2.8 Lens' MF ring features a very long 252° of rotation, making very precise focusing easy. This lens is very easy to perfectly focus at minimum focus distance and also at infinity, though having subjects stay in ideal focus over a range of ring rotation can give pause to perfectionists focusing at very long distances where even large subjects become tiny.
The focus ring is smooth, very nicely damped and has no play. Focus distances are printed on the focus ring (in both ft and m). The MFD (Minimum Focus Distance) and most-infinite (past infinity focus usually) focusing distances are hard stops, making focus setting marks repeatable. Subjects change size modestly over the focus length range, but the focus ring must be turned significantly for a sizable change to be realized.
Samyang does not publish the MM (Maximum Magnification) spec for this lens, but we can know that it is a low number. This lens gives up a little focal length at MFD and has a minimum focusing distance roughly 10% longer than the Zeiss 15mm f/2.8 lens. The 1mm longer Zeiss has a very low 0.11x MFD spec, so ... don't expect great things from the Samyang in this regard. Here is a table showing the 14mm and 15mm comparables followed by a variety of zooms covering the 14mm focal length or having wide angles and an f/2.8 aperture.
|Canon EF 14mm f/2.8L II USM Lens||7.9"||(200mm)||0.15x|
|Nikon 14mm f/2.8D AF Lens||7.9"||(201mm)||0.15x|
|Samyang 14mm f/2.8 IF ED UMC Lens||10.8"||(274mm)||n/a|
|Zeiss 15mm f/2.8 Distagon T* Lens||9.8"||(250mm)||0.11x|
|Canon EF 11-24mm f/4L USM Lens||11.0"||(280mm)||0.16x|
|Canon EF 16-35mm f/2.8L II USM Lens||11.0"||(280mm)||0.22x|
|Nikon 14-24mm f/2.8G AF-S Lens||11.0"||(280mm)||0.15x|
|Sigma 12-24mm f/4.5-5.6 DG II HSM Lens||11.0"||(280mm)||0.17x|
|Tamron 15-30mm f/2.8 Di VC USD Lens||11.0"||(280mm)||0.20x|
|Tokina 16-28mm f/2.8 AT-X Pro FX Lens||11.0"||(280mm)||0.19x|
The two dog images shared at the beginning of this review illustrate the close focusing capabilities of this lens.
While my extension tubes seem to have disappeared and I can't prove this out at the moment, expect the Samyang 14 to not be compatible with these. The combination of ultra-wide focal length and short native focus distance will likely render ETs useless on this lens, requiring a working distance shorter than the lens.
Overall, the Samyang 14mm f/2.8 Lens is quite small with a very small lens barrel, a large front element and an even larger built-in lens hood.
While this lens is basic in appearance, that big glass front element is gorgeous. Aided by that build feature, this lens has a solid weight for its size and feels very nice in hand.
The lens hood and other exterior barrel parts are made of quality plastic with exception of the aperture ring. It is also made of plastic and it has worked fine for me, but I'm not yet ready to give that ring the "quality" qualifier. The focus ring is rubber coated and consumes most of the lens barrel that is not aperture ring. Note that when gripping the lens for mounting or removal, you might find the lens hood to be the right grip surface as most of the barrel rotates freely and the focus ring rotates a lot of degrees.
As you already guessed (due to the lack of a gasket at the lens mount), this is not a weather-sealed lens. Use care if wet is possible.
While Samyang provides a mount alignment mark under the rear cap, I would appreciate this mark being visible from the side of the lens or when the cap is on.
When considering other lenses to compare this one to, only Canon and Nikon have direct focal length and aperture comparables. Zeiss adds a mm to their entry into this class, but it remains a close option. As I did in the close focus comparison table above, I'll add a handful of zoom lens options that either cover the focal length or have very wide focal lengths and an f/2.8 aperture.
|Model||Weight||Dimensions w/o Hood||Filter||Year|
|Canon EF 14mm f/2.8L II USM Lens||22.8 oz||(645g)||3.1 x 3.7"||(80 x 94mm)||n/a||2007|
|Nikon 14mm f/2.8D AF Lens||23.7 oz||(670g)||3.4 x 3.4"||(87 x 86.5mm)||n/a||2000|
|Samyang 14mm f/2.8 IF ED UMC Lens||19.5 oz||(552g)||3.4 x 3.8"||(87 x 96.1mm)||n/a||2012|
|Zeiss 15mm f/2.8 Distagon T* Lens||28.9 oz||(820g)||4.1 x 5.3"||(103 x 135mm)||95mm||2012|
|Canon EF 11-24mm f/4L USM Lens||41.7 oz||(1180g)||4.3 x 5.2"||(108 x 132mm)||n/a||2015|
|Canon EF 16-35mm f/2.8L II USM Lens||22.6 oz||(640g)||3.5 x 4.4"||(88.5 x 111.6mm)||82mm||2007|
|Nikon 14-24mm f/2.8G AF-S Lens||34.2 oz||(969g)||3.9 x 5.2"||(98 x 131.5mm)||n/a||2007|
|Sigma 12-24mm f/4.5-5.6 DG II HSM Lens||23.7 oz||(670g)||3.3 x 4.7"||(83.82 x 119.38mm)||n/a||2011|
|Tamron 15-30mm f/2.8 Di VC USD Lens||38.8 oz||(1100g)||3.9 x 5.7"||(98.4 x 145mm)||n/a||2014|
|Tokina 16-28mm f/2.8 AT-X Pro FX Lens||33.5 oz||(950g)||3.5 x 5.2"||(90 x 133.3mm)||n/a||2011|
For many more comparisons, review the complete Samyang 14mm f/2.8 Lens Specifications using the site's Lens Spec tool.
Here are the four closest-match lenses visually compared:
Use the site's product image comparison tool to visually compare the Samyang 14mm f/2.8 Lens to other lenses.
With the bulbous front element in the way, filter threads are not on this lens' feature list. The lack of front filter threads is a setback for a lens intended to be used, especially, for landscape photography purposes. There remain plenty of landscape uses for this lens, but not being able to use circular polarizer filters and not having even a rear drop-in filter slot for neutral density filters will give pause to landscapers considering the purchase of this lens. A workaround to this problem exists in the form of 3rd party adapters, though these adapters and filters are quite large (145mm or so). The Samyang 14 is not unique in this regard as the Canon and Nikon alternatives do not have front filter threads. The Zeiss 15 is the most-similar lens to offer front filter capabilities as of review time.
With a front lens element protruding so much, concern for protection of that front lens element is elevated. Fortunately, Samyang has addressed this issue with a nicely-sized built-in lens hood. While not completely protecting the front element from scratches and other concerns, it is a good compromise between coverage and overall size. The hood is constructed of rigid plastic with only slight flex that aids in absorbing impact.
Lenses with this front element design style require a wrap-around style lens cap for complete protection. It wasn't many years ago that many of us considered these caps to be a pain as they were constantly sliding off. Fortunately, such caps now generally clip to the inside of the hood and remain securely in place. The Samyang 14's lens cap has been working great.
Samyang includes a basic, lightly-padded pouch in the box.
The Samyang box picture:
The Samyang 14mm f/2.8 Lens' biggest selling point is perhaps its price. As of review time, you can easily buy 6 of these lenses for the price of just one Canon 14mm f/2.8L II Lens and 5 for the price of one Nikon 14mm f/2.8. Note that, with the focus confirmation chip, the Nikon version of the Samyang 14 is modestly more expensive and that this higher price is factored into these comparisons. The bottom line is that the Samyang 14 is a great value.
The Samyang 14mm f/2.8 Lens is available in Canon (reviewed), Nikon, Sony/Minolta (A and E) and Pentax K mounts along with versions for Fujifilm X and Four Thirds mounts. I always include a disclaimer in third party lens reviews, explaining that there are potential compatibility issues with these, typically involving a new camera and an older lens. However, the risk of incompatibilities between a fully manual lens and a DSLR is very minimal. I see the risk as low. Samyang provides a 1-year warranty.
The evaluated Samyang 14mm f/2.8 Lens was sourced online/retail.
I have mentioned the lenses comparable to this one throughout the review. Established is that the Samyang is, by far, the most wallet-friendly among the comparable primes. The Canon and Nikon 14mm lenses offer autofocus, a key feature that can be worth the price difference to some. The Zeiss 15 also lacks AF, but it has front filter threads to its advantage over the other options.
The Canon, Nikon and Zeiss all have noticeably less linear distortion. See how much enlarged the Samyang's center of the frame details are in this comparison?
While my experience with the Nikon 14 is limited to our standard test results, the Canon and Zeiss are sharper lenses at f/2.8, though they have more LatCA. Stopped down, all of these lenses become quite close in sharpness. The Canon shows the least amount of vignetting with the Nikon close behind.
The Zeiss will take up more room in your case and has the heaviest weight. It is also an amazingly well built lens, likely to far exceed the Samyang's life expectancy.
In the end, any of these lenses can be justified for certain needs, but the Samyang is by far the easiest to justify on a cost basis.
Most photographers would not put full frame 14mm at the top of their most-used focal length list, but most photographers can benefit by having this focal length in their kits. Images captured at 14mm can be very captivating and a welcome addition to one's photo portfolio. Simply shooting at this wide of an angle can be photographically educational.
Also educational can be photographing with a fully manual lens. Though this lens may slow you down in the field, it may also force you to take more care in the set up of your images. The wider the focal length, the easier to utilize I find fully manual lenses to be. Being ultra-wide makes this one very tolerable for a wide range of situations.
While I have addressed a list of shortcomings of this lens, the Samyang 14mm f/2.8 Lens' big deal is the image sharpness for the price. This lens is a big addition to the kit for a small price.
Bringing you this site is my full-time job (typically 60-80 hours per week). Thus, I depend solely on the commissions received from you using the links on this site to make any purchase. I am grateful for your support! - Bryan