Good Performance, Good Price: Samyang/Rokinon 85mm AF Lens

The Samyang/Rokinon AF 85mm lens comes with a soft pouch and generous, though plastic, lens hood. Controls are limited to an Auto/Manual Focus switch. Credit: Alan Dyer

A new 85mm lens from Samyang/Rokinon provides good astrophoto performance at a relatively affordable price. 

Plus: Sharp optics, light weight, and with auto-focus for normal use

Minus: Some residual chromatic and off-axis aberrations 

Summary: Available for select mirrorless and DSLR cameras, the new Samyang AF 85mm provides sharp, low-aberration image quality at a price much lower than premium auto focus 85mm lenses.

Who Is It For? Astrophotographers looking for a versatile modest telephoto for both nighttime and daytime use. 

For many years lenses from the Korean manufacturer Samyang have been a popular choice among astrophotographers. In North America their lenses are often sold under the Rokinon brand name. Under either badging, the lenses offer very good optical performance at bargain prices, often by forgoing features such as auto focus, which we astrophotographers can rarely use under the stars anyway. 

Comparing 85s

I’ve found an 85mm lens a great focal length to have in the kit bag, good for some nightscapes and for tracked closeups of constellations and regions of the Milky Way. Rokinon’s old (and still available) manual focus (MF) 85mm f/1.4 Aspheric served me well for several years, as it is quite sharp. It is a no-frills lens that has a manual aperture ring and with no electrical connection to the camera. So lens information is not recorded in the images’ metadata.

On the left is a quartet of images with the older Rokinon MF 85mm Aspheric; on the right a set with the new Samyang AF 85mm, each at one-stop intervals. The AF lens has less chromatic aberration, and less prominent diffraction spikes. Credit: Alan Dyer

At about $300 Samyang’s MF 85mm is among the lowest cost 85s on the market — for a reason. It lacks costly low-dispersion ED glass. As a result, it presents prominent chromatic aberration — stars are surrounded by blue halos. Stopping down the lens to f/4 reduces the halos but does not eliminate them. While the blue glows can be further reduced in processing, I found doing so often left stars with dark halos. 

Promising far better performance is Samyang/Rokinon’s 85mm f/1.2 SP (for Special Performance), also a manual focus lens, but with camera communication and two low-dispersion ED lens elements — but also a much higher price, usually about $1,000. I have not tested the 85mm SP model.

Seeking better optics than the older MF 85mm, but at a more reasonable price than the SP, I chose Samyang’s new AF 85mm, a fully auto focus lens with a single ED element, and in a light plastic but weather-sealed housing. The version I tested weighs just 660 grams (by comparison the 85mm SP weighs 1050 grams). 

I purchased the lens for Canon’s RF mirrorless mount, but an identical version is available for Sony’s E-mount mirrorless cameras. Shorter and lighter versions for Canon and Nikon DSLR cameras have a different lens configuration than the mirrorless lenses, so I can’t say if their performance would be the same as the RF version I tested. 

To add to the confusion, all the variations are available branded as either Samyang or Rokinon, with sometimes a notable difference in price. So shop around. 

On-Axis Aberrations

Compared to the older MF 85mm (as shown above), the new AF 85mm exhibited much lower levels of chromatic aberration. However, even at f/2.8, where I’d prefer to use a lens like this for most astro-imaging, false color isn’t entirely absent in the AF. 

The small level of chromatic aberration that remains at f/2.8 can be corrected in processing, as I show below, without undue harm to the image. Most raw processing programs have tools for reducing false color halos.

Defringe tools, such as in Adobe Camera Raw shown here, can reduce residual longitudinal chromatic aberration that adds the blue halos. Credit: Alan Dyer

While the AF 85mm has a maximum aperture of f/1.4, I judge it unusable for astrophotography when wide open. Stars are soft and aberrated even at the center of the frame. This aperture might be suitable only for soft-focus portraits.

Stopping the lens down to f/2 makes a huge improvement to image quality both on- and off-axis. This is as fast an aperture as I would recommend with this lens.

A quartet of images compares the sharpness of stars at the center of the frame of the AF 85mm at four apertures. The small image at top right shows the area of the frame being blown up for close inspection. Credit: Alan Dyer

At f/2.8, still plenty fast enough for tracked night-sky exposures, performance improves still further. Star images in the center of the frame are now very sharp and free of image-softening spherical aberration. 

The 9-bladed iris diaphragm adds a photogenic burst of diffraction spikes on bright stars that is not excessive or intrusive. 

Vignetting

As with most fast lenses the AF 85mm exhibits a lot of vignetting, or darkening of the frame corners, when used wide open at f/1.4. The corners appear about 2.25 stops darker than the center. At f/2 vignetting decreases notably, with the corners now 1.5 stops darker. At f/2.8 vignetting is down to 0.8 stops, and at f/4 is just 0.4 stops.

This shows the level of corner vignetting at f/2, severe but largely fixable in raw image processing using lens corrections. All test images were with the full-frame Canon EOS Ra camera. Credit: Alan Dyer

As illustrated here, applying lens corrections in processing can negate most if not all of the vignetting and “flatten” the field. Adobe software (Lightroom and Camera Raw) has a matching lens profile for the Samyang AF 85 and nicely corrected the vignetting automatically. 

Popular Adobe alternatives Affinity Photo, DxO PhotoLab and ON1 Photo RAW, while each having a lens profile for the AF 85mm, all did a poor job automatically correcting the vignetting. In fact, Affinity Photo did nothing at all.

Off-Axis Aberrations

Off-axis aberrations, such as astigmatism and coma, distort stars into streaks or seagulls at the corners. These, too, improve as the AF 85mm is stopped down, with aberrations progressively retreating to the extreme corners. But even at f/4 they aren’t entirely gone, though you have to pixel peep to see the residual aberrations that remain.

This quartet shows the extreme upper left corner of images taken at one-stop increments. Performance was identical at all four corners; there was no sign of lens decentering. Credit: Alan Dyer

At all apertures, lateral chromatic aberration, which turns stars into colored streaks at the corners, was very well controlled. 

The AF 85mm is known to provide a “warm” color cast to images, a trait likely to aid the lens’s main purpose, portrait photography. I found this characteristic of no consequence for astrophotography where we almost always have to apply a custom white balance in processing to correct sky discolorations. 

Mechanics

Being an auto focus lens, the AF 85mm, as many lenses do now, has no focus scale. While the focus ring can be turned manually, it turns continuously. There is no infinity stop. 

Rather than directly moving lens elements, the focus ring activates a motor in a “focus-by-wire” operation. So focusing at night can’t be done by pre-setting the lens to an infinity mark or to some predetermined point where you know stars are in best focus. 

However, manual focusing was precise and consistent. When turning the camera and lens back on, the lens returns to the focus point set the night before. 

The lens accepts front-mounted 77mm diameter filters, the same as many of my other lenses and filters. That was one reason I selected the AF 85mm over other 85s, as most require buying 82mm or larger, and therefore more costly filters.

In conclusion, I can recommend the new Samyang/Rokinon AF 85mm lens, especially if autofocus is important to you for non-astrophoto use. While its optical performance doesn’t match the best, the best can cost two to four times what this still economical 85mm lens costs. 

MSRP: $500 to $650 U.S. depending on the lens mount

Website: https://rokinon.com 

About Alan Dyer

Alan Dyer is an astrophotographer and astronomy author based in Alberta, Canada. His website at www.amazingsky.com has galleries of his images, plus links to his product review blog posts, video tutorials, and ebooks on astrophotography.

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