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Sony 135 Testing and Myth debunked

The Sony 135 STF – some tests and myth debunked

This is one of the most unique consumer lenses available. The design philosophy of this lens is to create the most pleasing bokeh, while having whatever that is in focus still being sharp. This is very different from a soft focus lens or a lens that performs very well in the center area but goes very soft at the corners.

There are many articles on the net talking about the design of this lens already, but few touches on how the lens works. I have also read quite a few misconceptions about this lens as well. Since I finally own one, I have decided to post a few test shots and want to debunk a few urban legends about this lens!

Myth – the double aperture rings creates the smooth bokeh.
If you take the lens off the camera and turn the “T stop / STF ring” towards T6.7 you can see the lens is stopped down with 2 aperture rings, one on top of the other. However, this is not how it operates in shooting conditions. You can only use just one of the two aperture rings when shooting.

T stop ring is set to “A” - The lens is wide open just like a regular modern SLR lens. The aperture can now be controlled via the input dial on the camera, going from f4.5 to f32. There is no f2.8 even the lens measured as an f2.8 max f stop lens. Apparently the Apodisation Element inside the lens also acts a ND filter, reducing the amount of light going through the lens, but not in an even manner. The effective T4.5 will be displayed as f4.5 on the camera instead. The photographer can now stop down the lens as he/she please just like a regular Alpha lens. When this lens is shot wide open the bokeh is just the same is shooting the lens at T4.5 (on the T stop setting).

When the T stop ring is set to anything other than “A”, this lens will now be at full manual mode, meaning the aperture can no longer be controlled via the camera. In fact, nothing will happen when the control dial is turned even if you are in aperture priority mode. The T stop ring is a step-less aperture ring with a circular opening, a 10-blade design that resembles classic lenses (usually RF lenses) with a full manual aperture. There are no springs to keep the lens at wide open at all times while stopping down to the preset f no. as the shutter fires. The minimum setting on the T stop is T6.7. There is no stopping down to f32 like the first aperture ring.

So what is the STF magic about? Go to the first image and read on.
Bokeh @ T4.5
Bokeh @ T4.5		 Bokeh @ T6.7
Bokeh @ T6.7		 T4.5
T4.5		 T6.7
T6.7
So what is the difference between wide open, f6.3, and T6.7?
So what is the difference between wide open, f6.3, and T6.7?		 f6.3
f6.3		 T6.7
T6.7		 Massive CA
Massive CA
Nice colors
Nice colors		 Conclusion (but not finished)
Conclusion (but not finished)		 STF vs 85L - Bokeh showdown
[ STF vs 85L - Bokeh showdown ]

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