Đánh giá samyang 12mm f2 8

Ống kính gồm 12 thấu kính được chia làm 8 nhóm, bao gồm 2 thấu kính thủy tinh (ASP) và 3 thấu kín tán xạ thấp (ED) mang lại độ phân giải tốt nhất cho hình ảnh. Ngoài ra, Samyang sử dụng lớp phủ Nano nhằm tối ưu hóa sự xâm nhập của ánh sáng, giảm thiểu hiện tượng lóe sáng và bóng ma. Với chiều dài tiêu cự tối thiểu 0.2m, nhiếp ảnh gia có thể chụp được các vật thể ở khoảng cách gần.

Các tính năng phần cứng

Ống kính với 7 lá khẩu độ khi đóng lại hoàn toàn tạo thành một hình ngôi sao hoàn chỉnh và đẹp mắt. Thân ống kính làm từ vật liệu nhựa Aluminum cao cấp tạo cho ống kính độ chắn chắn với tổng quan nhỏ gọn. Đồng thời, loa che sáng tháo rời hình cánh hoa giúp cản bớt luồng sáng không cần thiết tránh gây hiện tượng chói sáng và bóng ma.

Good nightscape shots have to be captured under ideal conditions. Well, just a cloudless sky will get you started anyway. I’m always looking for the next best piece of gear and darkest location myself. And around the start of this month, a particular dark location got proper recognition as the Dutch second Dark Sky Park. So let’s put location and gear together in this review of the Samyang 12mm f/2.8 for full-frame cameras.

In this review, I’m taking you to Lauwersmeer National Park, located in the north east of the Netherlands. It’s a Dark Sky Park now, which means that the night sky there is protected and the area is accessible for the public to enjoy as well.

As for gear, I screwed this diagonal fisheye lens on my D750. Which, if you can remember, is my favorite camera to date for landscape astrophotography (I like to call them nightscapes). With this 12mm lens on that camera, the diagonal sports a whopping 180 degrees. So get ready for whacky distortion in this review.

Samyang Lenses and Some Disclosure

Samyang Optics recently started building autofocus lenses. This 12mm fisheye is not of those. Now, some of you may know this lens as being built by Rokinon. It's the same lens, just marketed differently. This one should also not be confused with the 12mm f/2.0 CS. That’s regular, rectilinear wide-angle glass that’s been built for crop-sensor cameras.

Oh, before I forget, Samyang did not send me this lens for review. Instead, I bought a copy and would love to give you my unbiased thoughts. I’ve owned their 14mm f/2.8 before, and was very happy with that, aside from its mustache distortion. But that’s very easy to correct in post.

Whacky

First off, this of course is a fisheye lens. And I love it for that effect. It allows me to get dangerously close to my subjects for added dramatic effect. That up-close-and-personal workflow does have a few drawbacks though. Yeah, it’s hazardous. Even in landscape photography with no potentially dangerous animals, because you’re getting so close to your subject that you don’t really know when to stop getting close. While the minimum focus distance of 20.07 cm isn’t exactly macro work, it’s difficult to judge if that twig will poke in the front element or that you’re in the clear when building your composition.

https://500px.com/photo/170530745/the-signal-by-daniel-laan

And when you do get to the minimum focusing distance, how do you then get everything in tack sharp focus? At this setting and even at 12mm, infinity isn’t sharp. Or you’d have to dial in f/22. Let me tell you: Still no sharp infinity and detrimental to overall image sharpness due to diffraction. For me, that leaves focus stacking.

Buzz Lightyear Reference

Speaking about focus, it isn’t hard to focus at night with this lens. At f/2.8 (would you want to close the aperture at night?) the infinity focus marker on the lens was spot on my copy. Just use a head lamp and make sure the focus ring is set to the correct marker. That’s it.

But, because of the diagonal 180-degree field of view, the focus isn’t spot on all the way over the frame. In fact, you’d have to go beyond infinity to get the corners in perfect focus. That’s not good, but what can you do?

I accepted the focus flaw and shot this:

https://500px.com/photo/172082801/start-of-a-journey-by-daniel-laan

This was shot in a Dark Sky Park, right? So what’s that light pollution doing over there? Yeah, they were flaring off natural gas in the distance. I wasn’t too happy with that ball of fire after driving all the way up there, but it did create a complementary color contrast.

Coma

The item I know you’ve been waiting for. Since that focus flaw makes it difficult to accurately measure and judge lens aberrations, formal lab tests are hard to perform. It’s part of the reason why you’ve never seen solid head-to-head comparison of fisheye lenses. Coma is one of those aberrations. It (and another flaw called astigmatism) causes elongated streaks instead of points in bright light sources against a dark background (e.g., stars). Coma’s streaks look rather like the glow of a comet, from which it gets its name.

The Test

So here’s a real-world field test. Camera on tripod, point to zenith (which happened to contain Andromeda then) and focus at infinity. Well, the image center is at infinity:

The point of this image is to show you the differences in coma when we compare three apertures. These are shot at 30 seconds and ISO 4,000, with apertures of f/2.8, f/4, and f/5.6. The last of which you’re not going to shoot at unless you’re tracking the night sky with a purpose-built device that you put on top of your tripod. As for post-processing, I’ve left the lens correction tab alone, apart from chromatic aberration. Remember, it’s a real-world test. What point is there to testing if you’re never going to use it? So that’s distortion left off and vignetting too. It’s just Lightroom on this image as well, normally I go to great lengths in Photoshop to pursue my vision. A demo of which you see in the first two shots of this review. Here’s the comparison.

So there’s some amount of coma there that gradually becomes less apparent when stopping down. No surprise there. But what is surprising to me is that the coma isn’t that obvious at all when you look at a full screen version of this image. That’s a solid wide-angle performer.

Summary of Findings

That’s not much coma for any type of lens really. And the distortion can be used to your compositional advantage. You do have to learn how to work with that though. A fisheye can quickly become a gimmick rather than a tool.

The 12mm’s sharpness doesn’t disappoint either, although pixel peepers should be aware that there’s less sharpness in the corners than there is in the image center, due to them being slightly out of focus at infinity.

Conclusion: Is This Lens For You?

Don’t like whacky? Then be aware that you can “defish” your images rather easily nowadays. When you do that, the angle is still wider than on that 14mm I told you about earlier. But this lens correction is even easier to correct than the mustache distortion on said 14mm.

Fisheyes though, they’re meant to be whacky. It is part of their charm. The Milky Way looks a bit distant, but you can get so much of its plane in your shot, it’s insane. This particular fisheye is a solid wide-angle performer. But, to be fair, I haven’t had the pleasure of testing other fisheyes out there.

So, from an absolute standpoint; what’s the verdict on Samyang’s 12mm f/2.8 optical characteristics? If you’re looking for a new way to image the night sky and have a ton of foreground in your image, then this lens should definitely get on your gear list. Combine this very useful piece of kit with an excellent build quality which you can expect from Samyang, and you have a lens that should come with you on every trip to take pictures of the stars.