Quality and performances.
All in all, this is not better than the Batis 18mm Zeiss I used in the past but you have to consider that the Samyang is designed with very different purposes. That said, it is lighter, cheaper and with different a quality to its materials.
Wide open, the Samyang is sharp, but not terribly so. This kind of sharpness is excellent in the center, but there’s slight degradation at the edges, even on the apsc’s and experiences much stronger loss as you move to the full frame corners. Corners are pretty soft even at f/5.6. you have to close at least at f8 to get the best sharp lens.
Overall I’d judge edges to be good wide open, and very good stopped down.
There are some lateral chromatic aberrations but they are controlled and you can easily correct them with different software, as you can see in the sample images.
Astigmatism and coma into the corners are well controlled. This lens is nice for astrophotography.
Linearity is good, not perfect in my opinion: there’s very little linear distortion at the edges. That’s pretty common in wide angles lens (maybe Laowa works better but it’s again heavier and it’s also a manual focus lens).
Vignetting on an full-frame’s bodies is visible and needs correcting if you dislike it (about 1.5 stops worth), but stop down to f/5.6 and it becomes mostly negligable. Personally, I like a bit of vignetting, it’s more “moody” I would say.
Vignetting never quite goes away at non-diffracted apertures, by the way. For such a wide angle lens, the vignetting performance is decent, but that doesn’t mean that it doesn’t vignette. Wide open, without correction in raw files, you’ll absolutely see the corner fall off.
As a portraitist as I am, I would like to consider the bokeh feature on this lens. Bokeh in not the main feature you consider on a wide angle lens but, if you get close enough to your subject wide open, it might start to come into your scene in a very nice way. The bokeh you can get is really similar to the Samyang AF 45mm F2.8 FE, which is progressing and accurate, different frome the Sigma art 20mm F1.4 FE. The out-of-focus areas are regular with different distances from the subject.
Overall, just like the 45mm and the 85mm which I had the good fortune to try and use, this lens is another Samyang winner. Sharpness and contrast are good and the other features don’t really detract from that, though some of them have to be corrected in post-production.
That’s really cute as a wide angle light lens, a best buy in my opinion.
Why would I not like this lens? Materials are the worst thing but read another time the review, you will find the answer.
The good news is that if you want an autofocus 18mm lens that covers the full-frame’s cameras and delivers performance that looks good even at 42mp ( I also tried it on my sony a7rII), then you’ve found a cheap candidate lens in this Samyang, despite to the little materials quality.
This is a good companion to the Sony A7r series for when you want to go wide and get the best quality. I suspect that travel, street and landscape photographers will be the ones that most respond to this lens. But it’s not bad for night photography, either.
The resullt i salso good in video, it has warm colors as the other Samyang and you can do the best VLOG you are thinking about.
I certainly can recommend it, looking also at the price.