Samyang's "GM 135mm killer"... but for Astrophotography? - Samyang AF 135mm F1.8 Review

In recent years Samyang (Rokinon in North America) have gotten a handle on building some higher-end lenses than they were previously known for. Is their 135mm F1.8 portrait lens appropriate for use on the stars? Lets find out!
Samyang AF 135mm F1.8
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Tracked samples were tracked using the Fornax Mounts LighTrack II. (Fervent Astronomy is Fornax's North American Distributor):
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Vetting a lens for astrophotography can be a bit of a pain, as most reviews don't dive deep into lens performance when used on the night sky. As such, I have been compelled to create lens reviews specifically for astrophotographers, which dig into lens performance in somewhat exhaustive detail - all to uncover how the lens performs on the stars.
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To download samples and read up on some of the information discussed in this video, just follow this link:
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Into astrophotography and looking for some gear? Check us out:
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Clear skies!

[@matthewholt7858]

Awesome thanks for the review! I was really excited for this one as you can find this lens used for sub $500, which in photography math is "basically free" and while many reviews say it has great performance of general/portrait photography, I think this is the first astro review. Really strange X diffraction pattern? and stars overall, but stopping down to f2 I think the lens is plenty good in the center. I suspect that BlurX fixes all these issues. If you are going to do the Sigma and Sony 135s I would appreciate your opinion on what you think is the best one.The value of this one is going to be hard to beat.
One thing I noticed in your f1.8 shot was a vertical line, which I also see in my Sony a7r4. Is that just a sony sensor thing? It goes away when you stop down which has me confused and I need to stretch my images quite a bit before it becomes apparent.

[@FerventAstronomy]

Glad you found it useful. I have the pieces all filmed for the Sony 135mm review but still need to edit it together. Spoilers: in news that’ll surprise no one, the more expensive lens does indeed perform better. But the maths of what’s right for every individual is up to them specifically. Not sure what vertical line you’re referring to? The 60MP sensor is actually 4 separate smaller chips stuck together, so if you really push a file you can sometimes see the seams. Is that maybe what you’re seeing?

[@matthewholt7858]

​@@FerventAstronomy At 12:00 to the left of the bright star there is a grey vertical line. I think it's dead center of image so your explanation makes sense.
As for the Sony I agree it isn't shocking, but I am curious how much better it does. Thanks again for these reviews

[@FerventAstronomy]

@@matthewholt7858 Ahhhhh. That's a satellite trail, my friend. Probably some Starlink space junk, its barely possible to take a photo these days without one photobombing things.

[@charlesichkanian3088]

Bonjour
Je pratique l'astrophographie sérieusement depuis plus de 40 ans.
J'ai possédé des instruments de très haut niveau comme Astrophysics en astro ( 155 EDFS F7 ) autres APO Fluorines APQ Zeiss etc...mais aussi d'excellentes objectifs photos,
Seuls le champ stellaire deepsky permet d'analyser une optique dans son ensemble.
Quand j'ai vu ce test de votre part du Samyang 135 F1.8 , comment une optique aussi mauvaise peut être mis sur le marché.
J'ai pu tester 4 Samyang 12mm F2...tous mauvais avec des défauts différents.
J'avais reçu le Samyang 85 mm F1.4 mk2 pour mes Canon ( je suis aussi équipé en Fuji ) et je n'avais jamais vu en terrestre un tel niveau de chromatisme.
Je l'ai bien sûr retourné.
Samyang n'est pas fiable.
Il n'y a que le 135mm F2 qui répond vraiment aux astrophotographes.
Les étoiles sont restituées comme des billes parfaitement rondes sur l'intégralité du champ sans coma , sans astigmatisme et un sphérochromatisme insignifiant.
A F2.5 il est absolument parfait.
En instruments astro ( réfracteur APO ) , une étoile doit montrer un disque d'Airy parfait , sans ou avec un minimum d'aberration de sphéricité, sans sphérochromatisme , sans spectre secondaire aucun ou le plus minime possible ( variable selon formule optique , type verre ED ou Fluorine )

[@FerventAstronomy]

Merci pour votre commentaire ! Je pense que c'est un objectif que les gens veulent pour l'astrophotographie en raison de son ouverture. Et parce qu'ils veulent qu'il soit vrai qu'un objectif comme celui-ci peut à la fois être performant et peu coûteux. Comparé à quelque chose de plus haut de gamme comme un Astrophysics ou un Takahashi, cet objectif est assez peu performant, et les astrophotographes « hardcore » (comme vous) le reconnaîtront immédiatement. D'après ce que vous et un autre commentateur avez dit, il semble que le 135 mm F2 soit un meilleur choix.
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Thanks for your comment! I think this is a lens that people want to be good for astrophotography because of it’s aperture. And because they want it to be true that a lens like this can both perform well and be inexpensive. Compared to something higher quality such as an Astrophysics or Takahashi this lens performs quite poorly, and “hardcore” astrophotographers (such as yourself) will immediately recognize this. From what both you and another commenter have said it appears that the 135mm F2 is a better choice.

[@charlesichkanian3088]

Very very bad lens ! may be you copy ?
Samyang 135mm F2 is the Samyang excellent lens

[@FerventAstronomy]

Any time a lens exhibits poor performance the “bad copy” thing gets tossed around, but in this case I believe the lens performs perfectly to spec considering how it’s priced. It’s cheap, I expect it to perform like a cheap lens. My personal view is this: if I have to buy more than 1 of something like this to get a “good” copy then there is a serious quality control issue. No company should be letting “bad copies” out of their factory.