Originally Posted by Thalassa

The Rokinon is a fun little lens and, for its price, the image quality is quite good.

The maximum aperture of the lens is f/3.5. When using this aperture, the lens lets in the most light and you can use the lens in lower light or with faster shutter speeds while still getting the proper exposure. However, because of the low price, some compromises have been made with the optical design, and the image is not very sharp (especially at corners) even though it might be properly focused.

When the aperture is decreased (i.e. stepped down) to f/8, the image becomes sharper across the frame. The downside is that you need either more light or slower shutter speed (or a higher ISO setting) to get enough light for a proper exposure.

Rokinon lenses (they are, in fact, made by a company called Samyang but marketed under several brands) are manual focus only, i.e. you cannot use your camera's autofocus. This is nit a big deal with an 8 mm lens at it inherently has a fairly deep depth of field (DOF) and the DOF is even increased when the lens is stepped down. With f/8 (for historical reasons, the aperture numbers and actual aperture size move in opposite directions) aperture, an 8 mm lens's hyperfocal point on a m43 camera is about 55 cm. This means everything from about 30cm to infinity is always in focus.

What I do not recall of the top of my head (and am toolazy to check) whether you can use your camera's aperture priority mode with this lens or whether you must set the aperture manually from the lens. But this should be clearly explained in the manual.

Hope this helps.

Cheers,
T.