Pentax SMC DA 35mm f/2.8 Limited macro - Review / Test Report - Analysis
Lens Reviews - Pentax
Thursday, 21 August 2008 06:00
Article Index
Introduction
Analysis

Distortion

The lens shows a slight degree of barrel distortion (0.4%) which is not overly field relevant.

Vignetting

Typical for many dedicated APS-C lens the vignetting is somewhat more pronounced. At f/2.8 you can expect a decrease in corner brightness of ~0.8EV which can be visible in critical scenes. The problem is very reduced at f/4 and pretty much negligible from f/5.6 onwards.

MTF (resolution)

The Pentax lens produced very good resolution figures in the MTF lab. The center performance is very high straight from f/2.8 whereas the border quality is somewhat reduced here (still good to very good). The peak performance is reached around f/5.6 with an excellent center quality and very good borders. As usual diffraction takes its toll at smaller aperture settings - if possible avoid f/22.

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 generally well controlled below f/5.6 (<1px at the image borders) but the problem increases the further you stop down. The CA level may be somewhat disturbing at f/22 but then that's no mainstream setting anyway.

Bokeh

The quality of the blur in out-of-focus areas is something of a mixed bag. At standard focus distances the bokeh is somewhat prone to produce halos which can look rather nervous. This is slightly disappointing for this kind of lens.

The situation seems to improve in close-up situations although the more shallow depth-of-field does surely help here.

Verdict

The Pentax SMC DA 35mm f/2.8 Limited macro is a undoubtedly a high quality lens but it does not excel. The center performance is great straight from the max. aperture whereas the corner performance is slightly lower than expected for a "Limited" lens (still on a very good level in absolute terms). The lens produces only a very slight barrel distortion and quite moderate vignetting but lateral CAs are a bit on the high side for a newly designed fix-focal length lens. The bokeh can be busy at medium focus distances but it seems fine in macro situations. The pricing of the DA 35mm f/2.8 is fairly moderate (~320€/450US$) especially when considering the excellent build quality as well as its macro capabilities.

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