Laowa is a dab hand at creating unusual lenses and the Laowa 105mm f/2 STF lens is a case in point. It's one of the very few lenses that features an apodisation element.
The weighty metal lens features two diaphragms, one your regular f/stop aperture and another a T stop aperture (apodisation element) halfway up the barrel. In this case, the element is labelled Smooth Transition Focus (STF).
STF creates images with extra smooth out-of-focus areas while keeping the area in focus particularly sharp. It is THE selling point of the lens and the results are wonderful. When using the T Stop aperture wide open, you get perfectly circular bokeh with next to no chromatic aberrations (fringing).
It's impressive stuff and for the quality of images possible out of this lens, its RRP of £750 is very reasonable.
But, and it's a big but, this is a manual focus lens only.
I don't mind manual focus lenses, in fact I rather like taking manual control. But there are lens focal lengths and subjects that really benefit from autofocus and this is one of them.
Throughout testing the lens my hit ratio of sharp shots was much lower than I would like. Even with the large Nikon D850 viewfinder at my disposal and live view focus magnification, it's exceptionally difficult to obtain pin sharp focusing on the eyes at f/2.
In the end, I resorted to manual focus bracketing. Taking the same shot around 5 times in quick succession while making micro adjustments to focusing. That way I could ensure one of the shots was pin sharp on the eyes and discard the rest.
One other downside is that lens flare is a bit of a problem. I like to shoot towards the light for backlit portraits. Yet, when doing this the chances of substantial lens flare are higher than normal - I got a few shots that were totally unusable.
Otherwise, the image quality and control over lens distortion is top notch.
All being said, I enjoyed the precision required of me to get images that I am happy with. I may have numerous slightly blurry images in the review gallery, but this lens has sharpened me up.