After searching for months for the next lens upgrade for YouTube, I eventually decided on the Rokinon 35mm T1.5 Cine lens. Though I had initially considered using a 50mm f1.8 (nifty fifty), the small focus ring and poor build quality of those lenses turned me off. Also, since I'm using an APS-C sensor camera, the 35mm field of view was a lot more useful for product reviews. This lens has now become my most used camera lens and I definitely recommend it for anyone who needs a high quality prime lens without much cost. Image Quality
The image quality from this lens is very sharp, but starts to soften when opened to T1.5. This is typical of most lenses, and I find the best balance between depth of field, sharpness, and low light performance on this lens is at around T2.8, so that's where I typically use it.As for chromatic aberration, there was a little bit of fringing at T1.5 in high contrast (black on white) areas, but this happens on a lot of lenses. It was a little more pronounced when the image was slightly out of focus as well, and could be seen even in video mode. When stopped down to T2.8, this pretty much completely went away.
Focus
The overall experience with focusing the lens is really good. The focus ring is very smooth to turn and has just enough stiffness to it. The smoothness also helps when pulling focus by hand instead of with a follow focus, since there isn't really any shake added. I did buy this lens with the long term goal of eventually adding a follow focus, but it definitely is good on it's own so that's not entirely necessary. If I did decide to in the future, the focus ring has a gear for a follow focus built in, so there's no need for those ugly add on gears.
Another important feature of the focus ring are the distance indicators. This ranges from 0.3 m to just past infinity and makes focusing a lot easier. There are also indicators that show the range of focus at certain aperture. The largest depth of field being at T22, which allows everything to be in focus from 1m to infinity. This is especially helpful at night when talking long exposure shots since the low light and added noise can make manually focusing with the camera display very difficult.
The one concern with this lens is there is a considerable amount of focus breathing. Basically this means that the focal length changes slightly as you adjust the focus of the lens, and this can change your framing slightly. If considered when framing the shot, it's not too big of an issue, but it is something that can catch you off guard if pulling focus and not accounting for it.
Aperture
A declicked aperture can also allow you to quickly change the amount of light entering the camera while recording and you'll get a smooth transition. This helps when light conditions change quickly, like when moving the camera from an indoor shot to outdoors without stopping. This can also be done with variable ND filters, but they have limitations and can degrade the image quality. That isn't to say there aren't problems with changing the aperture like this, since you're also affecting your depth of field at the same time.
The aperture ring quality feels similar to the focus ring and is very smooth, though much smaller. My one complaint about this is how close the ring is to the body, since it can be difficult to access on some camera rigs. Like the focus ring, the aperture ring is also geared.
Without electronic communication between the lens and camera, there's no control of the aperture with the normal buttons. Your camera also won't save information about the lens focal length and aperture like it does with normal lenses. Since we're talking about this lens from a video perspective, this isn't much of an issue. It is definitely something to consider for photographers though, since it makes it more difficult to apply a lens profile when correcting for issues like chromatic aberration. Without aperture information, it's also difficult to judge the exposure when shooting in manual mode for stills since the exposure on the screen doesn't match the image well. This isn't a problem for video mode.
In some cases, having a manual lens like this is actually a huge advantage. I was looking for a way to get close up shots of some products I was review a while back. After looking at macro lenses, I just couldn't justify the price for the few shots I would be using it for. Instead, I decided to use extension tubes. Since the lens is completely manual, I was able to get cheap Fotodiox extension tubes without any electronics, full article on that here.
The Rokinon 35mm lens has 8 aperture blades inside, compared to some cheaper lenses which may only have 5 or 6. This allows for much rounded bokeh when stopped down, since the shape of lights becomes octagonal instead of pentagonal or hexagonal.
Build Quality
This Rokinon lens is mostly a hard, durable plastic, but it does have a metal camera mount. The lens is fairly heavy, but not to the point where it's hard to use or requires lens support. The only time I would recommend using lens support is if you're using extension tubes since the added distance increases the torque on the lens mount at the camera. This can also be a bit of an issue on some cameras if you choose to adapt the lens, since the weight is placed further out from the body.This extra weight of the lens actually helps to make up for the lack of image stabilization. The heavier rig experiences quite a bit less jitter. It actually find handheld footage with this lens more usable than my kit lens with stabilization at the same focal length.
Unlike some other Rokinon lenses such as the 14mm, this lens can take a standard 77mm lens cap. This is super helpful since it's very difficult to replace missing lens caps on those Rokinon lenses. Additionally, it has a removable lens hood. I've found it can get in the way, especially with extension tubes. The lens hood is fairly flimsy plastic, so I would be careful not to break it. Luckily if it breaks, it does come off, unlike the other lenses which are stuck with a busted hood.
Mount Options
This lens has a few different versions that are compatible with Canon EF, Sony E-mount, Micro Four Thirds, and Nikon. My recommendation is to get a Canon EF version if there is a compatible adapter available. Since the lens has no electronic communications, you're not really loosing any functionality. The advantage is the Canon EF mount versions are more widely available on the used market, and they tend to hold their value better.Cine DS Version
For those who may be wondering about the Rokinon Cine DS version of this lens, they are fairly similar, but with a few improvements. The new lenses do have an updated coating on the glass which slightly improves color and image quality. They also standardized the position of the focus and aperture gears across all their lenses, making it easier to switch between them if you have a large rig. For me, this wasn't worth the additional cost.Overall this lens is a good alternative to the Canon 35mm f1.4, at only a fraction of the price. I wouldn't recommend it for professional photographers, since autofocus and electronic lens communication is definitely important, but it's great for video. This is a great lens for anyone looking for a sharp prime lens to get into video work, especially if planning on using manual focus only.