The Rokinon 135mm F/2 was Built for Astrophotography
In this post, I’ll explain why I think the Rokinon 135mm F/2 is the perfect addition to an arsenal of astrophotography lenses.
Deep sky astrophotography is often associated with a camera and telescope, but the truth is there are a lot of great camera lenses for astrophotography out there. In the past I’ve covered a number of different lenses, from the Rokinon 14mm F/2.8 to the Canon EF 300mm F/4L.
As you know, camera lenses come in varying focal lengths, apertures, and optical quality. Astrophotography is one of the ultimate tests of lens quality, as long exposure photography of deep sky objects in space can highlight issues that are hidden during daytime photography.
In this post, I’ll share my results using an affordable prime telephoto lens for astrophotography, the Rokinon 135mm F/2.0 ED UMC. The version I have has the mount for Canon EOS camera bodies, but there are several different lens mounts available on Amazon.
My Canon EOS 60Da with the Rokinon 135mm F/2.0 mounted to a Fornax Mounts LighTrack II.
This lens is available for several camera mounts, including Nikon, Sony, Pentax, Samsung, and Fuji. I purchased this lens for the purposes of wide-field deep sky astrophotography from my light polluted backyard (shown below), and when traveling to a dark sky site.
Taking images at this focal length from the city will swell issues with gradients, especially when shooting towards the “light dome”. For this reason, a combination of a good light pollution filter, and the use of flat calibration frames is recommended. Before I go any further, I’d like to share a photo from Gabriel Millou of the Andromeda Galaxy using a Canon 1300D.
The Andromeda Galaxy using the Rokinon 135mm F/2.0 ED UMC lens.
To see even more example photos using the Rokinon 135mm lens (or Samyang branded version), go ahead a perform a search on Astrobin or Flickr, with the appropriate filter. I think you’ll find that this lens is behind some of the most amazing wide field astrophotography images online!
The Rokinon 135mm F/2 ED UMC
The full name of this lens is the Rokinon 135mm F/2 ED UMC, with “ED” standing for extra-low dispersion, and UMC referring to the “ultra multi-coated” optics. This is a fully manual lens, meaning that it does not have autofocus, and you must manually select the f-stop using the aperture ring at the base of the lens.
Manually focusing a lens for astrophotography is nothing new, but the manual aperture ring adjustments may feel a little strange at first.
Rokinon lenses are made in Korea, and so is the Samyang variation. The full extent of the relationship between Rokinon and Samyang is unknown to me, but the packaging on my lens says “Technology by Samyang Optics”. I typically shoot with Canon lenses, but the potential for low light photography (whether that’s astrophotography or the ability to film at dusk) caught my interest.
The diameter of the lens is 77mm, with a non-rotating filter mount on the objective lens. The lens hood is removable (and reversible), which makes packing the Rokinon 135mm away into the included lens pouch possible. The presentation, and hands-on look and feel of the 135mm F/2 lens is impressive considering the reasonable price of this lens.
The aperture range of this of this lens is F/2 to F/22, with 9 diaphragm blades (aperture blades) that work in harmony to set your f-stop. The aperture ring is marked with each f-stop, and you need to manually click through F/2 – F/22 and watch the blades do their work. It’s actually kind of neat to watch!
I ordered this lens on Amazon, utilizing my Amazon Prime membership. The lens arrived next day, less than 24 hours after I hit the order button. The lens came in a handsome box, with core specifications and a lens construction diagram printed on the side. The Rokinon 135mm F/2.0 includes a lens hood, lens pouch, front and rear lens caps, and a 1 year Rokinon manufacturer warranty.
Overall, the lens feels very solid and well constructed. The finish and texture of the Rokinon 135mm F/2 is a step up from the 14mm F/2.8 I ordered a few years ago.
The spec sheet for the Rokinon 135mm F/2 boasts a number of qualities, with the ones listed below being the most important when it comes to night photography and astro. Based on my handful of experiences with this lens in the backyard, I have found these traits to hold true.
- Low-Light Performance
- Low Chromatic Abberation
- Low Flare and Ghosting
The image below shows a region of Sagittarius including many deep sky objects in the field. The photo itself is nothing special, as my light polluted backyard skies require several hours worth of integration to produce a pleasing image. However, it is a great point of reference for the field of view you can expect with this lens.
A portion of Sagittarius including the Lagoon Nebula and Trifid Nebula. 42 x 90-seconds at ISO 400.
The Rokinon website lists this lens as being useful for portraiture photography, and most telephoto applications. The shallow depth of field present at it’s maximum aperture does indeed create a pleasing bokeh.
The lens hood is not petal shaped, which is great news for those using this lens for astrophotography. The flat lens hood design allows you to easily take flat frames with the Rokinon 135mm using the white t-shirt method, or using a flat panel.
I should mention that I have only tested this full frame lens using my astrophotography DSLR’s, all of which are crop-sensor camera bodies. This creates an effective focal length of roughly 200mm, a useful magnification for a wide variety of astro-imaging scenarios.
I am no stranger to the full manual control of this lens, for both aperture and focus. The Rokinon 14mm F/2.8 was the first lens I had ever used like this, and these aspects do not hinder the astrophotography experience whatsoever.
A Full Frame, Prime Lens
The Rokinon 135mm F2.0 is considered to be a full frame lens, because it can accommodate a full frame image sensor with its 18.8 degree angle of view. In this review, however, I am using the lens on a corp sensor (APS-C) Canon EOS 60Da, which puts the field of view at 12.4 degrees.
“Prime” means that this lens is fixed at 135mm, it is not a zoom lens that allows for focal length adjustments. Prime lenses are typically lighter as they do not need the additional glass and mechanics required to zoom at varying magnifications.
Generally, prime lenses have a reputation for being slightly sharper, and I have found that to be true whether I am shooting a nebula, or a Scarlet Tanager.
The optical design includes one extra-low dispersion (ED) lens element to control chromatic aberration, and “ultra multi-coatings” (UMC) to both improve light transmission and reduce flare.
The flat lens hood is great for taking flat frames after a night of astrophotography.
Low Light Capabilities at F/2.0
The F/2.0 maximum aperture of the Rokinon 135mm lens offers a chance to collect a serious amount of signal in a single shot. This allows for less aggressive camera settings for night photography such as using a lower ISO setting, and even a shorter exposure.
Of course, when it comes to astrophotography, this can create some challenges as well. Focusing a “wide open” F/2 lens is demanding of the optics, especially on a field of stars in the night sky.
One way to combat potential soft images and chasing perfect focus all night is to stop the lens down to F/2.8 or even F/4. Your images have a chance at remaining sharper once critical focus has been achieved, but now you have lost the extra light gathering power you wanted. It’s a trade off, and one that seems to surface time and time again in this hobby.
Although typically unused in astrophotography, I did get a chance to see the beautiful bokeh this lens creates when shooting at F/2. The aesthetic quality of the blur in the out-of-focus parts of the image are buttery smooth and soft.
What I Really Like
Although this lens feels solid, it is rather light when compared to a telescope. When coupled with my Canon DSLR camera, the entire system weighs just over 3 pounds. That means that doesn’t require a robust equatorial telescope mount as a larger, heavier telephoto lens would.
A camera tracker (or “star tracker”) is necessary for long exposure deep sky astrophotography, but a compact model such as the iOptron SkyTracker or Sky-Watcher Star Adventurer will do just fine.
This lens has a long focus adjustment ring, with great tension. The focuser adjustment rotates roughly 270 degrees, meaning fine tuning on a bright star is more precise. You’ll never have to worry about losing your position just by touching the lens, but you can always tape the position down to be sure.
The Rokinon 135mm F/2.0 ED UMC is one of the most affordable and practical lenses for astrophotography on the market. Sure, the “Nifty 50” is an incredible value (and a LOT cheaper), but the 135mm puts you within range of some of the best astrophotography targets in the night sky.
I’ve spent a handful of nights testing this lens in my Bortle Scale Class 6/7 backyard, and my results live up to the hype it gets in terms of astrophotography performance.
Comparable Lenses (Chart)
|Brand||Focal Length||Maximum Aperture||Price|
|Canon||135mm||F/2.0||$999 (B & H)|
|Nikon||135mm||F/2.0||$1,391 (B & H)|
|Sony||135mm||F/1.8||$1,898 (B & H)|
Over the years, I’ve shot deep sky targets at varying focal lengths from 50mm to over a 1000mm. The closest I’ve been to the 135mm range is 105mm on my Canon 24-105 zoom.
Not only does the Rokinon 135 add additional reach, but I can also now shoot at F/2, instead of F/4 on the Canon. Below, are a few examples of astrophotography images I’ve taken with lenses of varying focal lengths.
As you can see, the magnification of the lens used will dictate the type of projects you shoot.
- The Great Rift of the Milky Way – Rokinon 14mm F/2.8
- Mars meets Pleiades – Canon EF 24-104mm F/4L
- Wide-field Sadr Region – Rokinon 135mm F/2.0
- The Carina Nebula – William Optics RedCat 51
So what’s so great about shooting at 135mm anyway?
The RedCat is deeper at 250mm, and after that you’re into 300-400mm territory which pulls galaxies and nebulae even closer. Why take a step back from 250 to sit between the RedCat and the 24-105?
It’s all about framing.
Image Scale at 135mm
From the moment I reviewed the first sub-exposure on the display screen of my camera, I feel in love with the mid-range magnification of a 135mm lens. My first shot was a section of the constellation Sagittarius that included the Lagoon Nebula, and Trifid Nebula.
If you want to preview the image field you can expect with a particular camera sensor and lens combination, Stellarium features a useful tool. The Image Sensor Frame tool lets you enter in the size of your camera sensor, and focal length of your lens (or telescope) to display a frame over the star map.
This is a very practical way to plan your next astrophotography project, and especially handy when using a wide field lens like the Rokinon 135mm F/2.
You can use Stellarium to preview the image scale with the 135mm lens and your DSLR.
At 135mm, you can get really creative about the object or objects you shoot and where you position them within the frame.
And because you can shoot between F/2 and F/4, plenty of light reaches the sensor in a relatively short exposure. This has several advantages from less demanding tracking accuracy, to being able to use a lower ISO setting.
The Downsides of this Lens
Now, I have to admit that up to this point, it sounds a little too good to be true. The downsides of this configuration are that shooting wide open can make focusing difficult.
The focuser adjustment ring on the Rokinon 135mm F/2 is excellent, but fine tuning your critical focus on a bright star at F/2 will take some trial and error to get right. You may need to refocus your subject as the temperature changes throughout the night.
You may need to stop down to control star bloat, and that’s exactly what I’ve done with this 135. I’ve set the f-stop to F/2.8, to sharpen up the stars a bit. In fact, in my test shots, I noticed that the red channel was a little softer than green and blue. To remedy this, I reduced the star size in post, and I started shooting at F/4 to really tighten things up.
Also, as creative as the wide field 135mm focal length is, it’s not practical for smaller DSO’s and most galaxies. Stick to Andromeda, and skip the Whirlpool.
The Andromeda Galaxy (Cropped). Canon EOS 60Da with the Rokinon 135mm F/2 lens.
I have heard others mention that this lens has a “plasticky” build quality, but I believe this aspect has been improved. The model I use feels solid and the barrel is constructed with metal.
The lens is not weather sealed, so you definitely don’t want to leave your camera and lens (and your tracking mount!) in the rain. There’s no image stabilization on the Rokinon 135mm F/2 either, but that’s a non-issue for amateur astrophotographers.
The North America Nebula captured using the 135mm lens with a clip-in Ha filter.
Recommend Astrophotography Targets for this Lens
I’ve captured a lot of deep sky astrophotography targets from the northern hemisphere, but I’m usually in too deep to capture an entire region of space at once. Here is a short list of great astrophotography targets to shoot at 135mm with this lens:
- Orion’s Belt (Including the Horsehead Nebula, Orion Nebula, and M78
- The Witch Head Nebula including Rigel in Orion (Careful with star reflection!)
- The Rosette Nebula and Surrounding Nebulosity
- Cygnus, including the North America Nebula and Pelican Nebula
- The Sadr Region in Cygnus including the Crescent Nebula
- The Blue Horsehead Nebula in Scorpius
- The Rho Ophiuchi Cloud Complex in the constellation Ophiuchus
Below, is an incredible example of the types of projects possible with the Rokinon 135mm F/2.0 lens. The following image was captured by Eric Cauble using the Samyang branded version of this lens.
The Sadr Region in Cygnus, including the Crescent Nebula by Eric Cauble.
Since Eric was so generous to share his images with me, I had to include his photo of the Rho Ophiuchi cloud complex as well. This photo was captured with the Samyang 135mm F/2 lens using a UV/IR cut filter and a QHY168C dedicated astronomy camera.
The Rho Ophiuchi Cloud Complex by Eric Cauble using the Samyang 135mm F/2 lens. See full-size version on Astrobin.
With an effective focal length of roughly 216mm when coupled with a Canon crop sensor body, the field of view is nearly identical to the one you’d find on a full frame camera with a 200mm telephoto lens. That’s quite a jump from 135mm, so the camera body you use with this lens may change the types of targets you shoot.
I can’t wait to try this lens out during the winter months on some wide field targets in Orion. The colder temperatures will make DSLR astrophotography much more practical, and there are plenty of great targets to choose from.
During the frigid months of winter, my motivation to spend over an hour setting up my complete deep sky imaging rig dwindles. However, stepping outside to polar align a small star tracker and attach a DSLR and lens is quick and painless.
In these situations, a portable, wide-field imaging rig wins.
Star parties or dark sky excursions are another great time to use a camera lens in place of the telescope. Not only does it let you travel light, but impressive wide field projects are often more successful when captured under a dark sky.
For those of you that like to “pixel-peep”, have a look at the single image frame captured using the Rokinon 135mm F/2.0 ED UMC at F/4. The image is a 90-second exposure at ISO 400 using a Canon EOS 60Da. The inset picture is a magnified view of the bottom right corner of the frame.
A single, 90-second exposure using the Rokinon 135mm F/2.0 ED UMC at F/4.
I hope that this post has provided some practical insight into a popular camera lens for astrophotography. If experience has taught me anything, it’s that the practical, pain-free equipment that gets the most use under the stars.
This lens is available on Amazon for most camera bodies. Make sure to select your camera mount when checking the price (Check current price). If you have pictures taken using the Rokinon 135mm F/2 lens, please feel free to share your results in the comments section (links to Astrobin, Flickr or your personal gallery are fine).
List of Compatible Cameras (Mounts)
- Sony E
- Fuji X
- Nikon AE
- Samsung NX
- Pentax K
- Sony A
- Micro 4/3
Complete Lens Specifications (Canon)
- Model: 135M-C
- MSRP: $599
- UPC: 0-84438-76410-9
- Focal Length: 135mm
- Maximum Aperture: F2.0
- Coverage: Full Frame (FX)
- Optical Construction: 11 Glass elements in 7 Groups
- Aperture Range: F2.0 to F22
- Diaphragm Blades: 9
- Coating: Ultra Multi-Coating
- Minimum Focusing Distance: 2.6ft (0.8m)
- Filter Size: 77mm
- Lens Hood: Removable
- Maximum Diameter: 3.2” (82mm)
- Weight: 29.20oz (830g)
- Length: 4.80” (122.1mm)
Download the User Manual
- Samyang 135mm F/2 ED UMC Review (Camera Labs)
- Does a F/2.0 lens become F/2.8 when used on a crop sensor camera? (Dpreview)
- Use the 500 Rule to find the Perfect Exposure Length for Astrophotography