Pentax SMC DA 35mm f/2.4 AL - Review / Lens Test - Analysis
Lens Reviews - Pentax

Distortion

The Pentax lens shows a slight degree of barrel distortion (0.8%). This is usually not objectionable.

Vignetting

The 35mm f/2.4 AL is a dedicated APS-C design. However, despite its small image circle there's only a comparatively moderate light falloff at max. aperture (0.7EV). This may be visible in certain situations but it's not a field-relevant issue anymore from f/3.2 onwards.

MTF (resolution)

The Pentax DA 35mm f/2.4 AL may be a very affordable lens but thanks to the moderate max. speed it is capable of delivering very sharp results throughout most of its relevant aperture range. The center quality is already excellent at f/2.4 and the borders/corners follow on a very good level. There's a slight increase in performance towards f/3.2 but generally the characteristic remains more or less constant between f/3.2 and f/5.6. Diffraction is starting to have a slight impact at f/8 and a little more so at f/11 but even so these settings remain perfectly usable.

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)

The amount of lateral CAs (color shadows at harsh contrast transitions) remain low at around 0.6px on the average at the image corners. This is usually not relevant anymore.

Bokeh

One of the primary usage scenarios for a large aperture lens is to seperate the main subject from the background. In such an image the quality of the bokeh (out-of-focus blur) is of major significance. The Pentax lens does a rather average job here which is typical for lenses with aspherical elements. Out-of-focus highlights can show an outlining effect and aperture shape gets already visible at f/3.2 - the latter aspect is an effect of the non-curved blades.

The background blur is quite smooth (left image crop below) whereas the foreground blur can be a little more nervous (right crop).

Bokeh Fringing / Longitudinal Chromatic Aberrations (LoCA)

Bokeh fringing is a color fringing effect in the focus transition zone showing a purple halo in front of the focus zone and a green one beyond. Typical for fast lenses the issue is very pronounced at max. aperture whereas it's not overly significant anymore at f/4.

Move the mouse cursor over the f-stop marks below to observe the respective LoCAs
f/2.4 f/4




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