Sony 100mm f/2.8 macro (SAL-100M28) - Review / Lab Test Report - Analysis
Lens Reviews - Sony Alpha/NEX (APS-C)
Wednesday, 30 April 2008 04:00
Article Index
Introduction
Analysis

Distortion

Typical for all macro lenses the Sony 100mm f/2.8 macro produces images which are basically free of distortion (0.03%).

The chart above has a real-world size of about 120x80cm.

Vignetting

The Sony 100mm f/2.8 is a full format lens and as such enjoying the usual sweet spot advantage when used on an APS-C DSLR. Within this scope the lens shows already marginal vignetting at f/2.8 (0.3EV) and the problem is absolutely negligible from f/4 onwards.

MTF (resolution)

The Sony 100mm f/2.8 macro produced very good to excellent resolution figures in the MTF lab. At f/2.8 the quality is already on a very high level and you can squeeze out a little more when stopping down to f/5.6, the excellent sweet spot of lens. Typical for all lenses diffraction has stronger impact beyond f/11. The results are still perfectly usable at f/16 but f/22 is beyond the edge. The rather low numbers @ f/22 suggest a smaller effective aperture than indicated at this setting (probably f/27ish). In theory you can stop down to f/32 but don't expect an acceptable quality level here anymore.

Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations

Chromatic Aberrations (CAs)

Lateral chromatic aberrations (color shadows at harsh contrast transitions) are very well controlled with an average pixel width between 0.27px and 0.53px at the image borders. Generally this is nothing to worry about in field conditions.

Bokeh

The quality of the bokeh is a primary playground for a macro lens and the Sony lens is capable of producing very decent results here. The circular aperture shape in out-of-focus highlights remains perfectly intact at f/2.8 and f/4. There's a bit of a one-sided outlining effect. The blur is very smooth and uniform. However, you may also notice the rather massive amount of longitudinal chromatic aberrations in the cards - more on this in the next chapter.

You can download the full-size images here:

Longitudinal (Axial) Chromatic Aberrations (LoCA)

LoCAs (non-coinciding focal planes of the various colors), sometimes called "bokeh CAs", can be a problem in field conditions. As you can notice below the halos have different colors - magenta (red + blue) in front the focus point and green beyond. The problem is rather pronounced at f/2.8 and f/4 and still visible at f/5.6. This is not overly impressive.

Move the mouse cursor over the f-stop marks below to observe the respective LoCAs
f/2.8 f/4 f/5.6

Verdict

The Sony 100mm f/2.8 macro is able to produce very sharp results combined with a negligible amount of distortions, vignetting and lateral CAs. However, longitudinal (axial) chromatic aberrations can be quite a problem in out-focus areas (f/2.8-f/5.6) resulting in a magenta to greenish tint in some situations - this is not unusual but unfortunate nonetheless. The build quality of the lens is fine although it doesn't win any crown when looking towards the competition a la Micro-Nikkor AF-S 105mm f/2.8 VR or the Canon EF 100mm f/2.8 USM macro. Same goes for the AF speed which does still rely on the slotted drive screw rather than Sony's faster SSM (ultrasonic AF drive). The biggest problem of the Sony 100mm f/2.8 macro is probably its price tag - at around 680€ or 580US$ it is substantially more expensive than the third-party alternatives without offering much if anything on top.

Optical Quality:    
Mechanical Quality:
Price/Performance:
      
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