Review: Sony 135 f/2.8 STF on Sony A99

A couple of months ago we rented a couple of lenses for an assignment in Napa Valley: along the Zeiss 16-35 f/2.8 to be used for indoors, I also rented a copy of the Sony 135 f/2.8 STF, pushed more by curiosity than actual need. This is a unique and daunting lens at first sight, it's big, built like a tank and it doesn't autofocus: the apodisation element that renders the silky-smooth bokeh it is so well known for prevents the phase-detection sensors from doing their work, forcing to go all manual. Having myself never engaged in the dark arts of manual focusing and always relied on the magic of the AF module for pretty much everything, I was preparing to stare at countless out of focus shots mercilessly heading to the electronic bin.

How wrong I was.

The bokeh is obviously delicious, smooth, silky, insert your drooling word here, but coupled with the A99 EVF and focus peaking the lens is also a joy to use: the apodisation element doesn't prevent the A99 from recognizing and highlighting edges that are in focus, since the algorithm runs in image space, based on the data captured by the main sensor. Focusing is a matter of rotating the very smooth focus ring until the portion of the frame you want to focus on is highlighted and snap away, knowing the result will be very, very, sharp where it is intended to. The color rendition is also superb: the image above has been barely touched in post (click for a larger view) just to remove small imperfections: a fantastic concerted effort by the camera/lens combo.

Back to focusing, the keeper rate was extremely high through the entire weekend both with static (easy) and moving objects.
Here's a shot of +Lina Mosashvili fooling around in a mustard field: I asked her to not stand still to practicing my focusing technique, especially with the 135 STF for this review. The separation between subject, foreground and background this lens can achieve is just godly.

From the same mustard field, here's an image I was very happy to include in my stock portfolio: yes, it's just a flower, but that bokeh...

I can't wait to rent the Sony 135 STF again and try it out on more portraits and, why not, food photography.

The STF has also a dedicated aperture ring that controls a secondary aperture with ten blades that can be steplessly set between T/4.5 and T/6.7: it can be used to tweak the amount of light transmitted and the depth of field. When the dedicated aperture ring is set to A, the primary aperture is controlled by the camera. The system is rather confusing, but once wrapped your head around it, it allows for some very fine control. I simply left it at T/4.5 and rolled with it. This lens is meant to be used wide open anyway.

The APD element is not only unmatched bokeh, but it also decreases light transmission by about 1.5 stops that might rather soon force to increase ISO when not shooting in bright conditions: that is why the 135 STF is marked as T/4.5 which means that the light transmitted when, for example, the lens is at maximum aperture is the same as the light transmitted by an equivalent lens stepped down to f/4.5. In other words: this is not a bright lens.
On the other hand, the A99 doesn't suffer much from pumping up ISO, which reinforces the idea that the Sony 135 STF and the A99 are a match made in heaven by the Gods of Photography for us mere mortals: get one, go out and shoot.

Thumbs up:
  - Fantastic bokeh
   - Very, very, very sharp
   - Built like a tank

Thumbs down:
  - Manual focus only (is it really a problem now?)
  - Hefty price tag for a very specialized lens
  - Not a fast lens