Zeiss Distagon T* 25mm f/2.8 ZF (on Canon EOS) - Lab Test / Review - Analysis
Lens Reviews - Canon EOS (Full Format)
Article Index
Introduction
Analysis

Distortion

The Zeiss Distagon 25mm f/2.8 produces a moderate degree (~1.8%) of barrel distortion. This is about average for a prime lens in this class.

Vignetting

The vignetting characteristic seems to be a real weakness of Zeiss Z-series lenses when used on full format DSLRs. The Distagon shows a fairly extreme deterioration of ~2.4EV at f/2.8 - this will be visible in most scenes. The problem is still very pronounced at f/4 (@ ~1.4EV) but it's not overly significant anymore from f/5.6 onwards.

Here're some sample images from the lab:

f/2f/2.8

MTF (resolution)

The Zeiss lens produced disappointing resolution figures in our MTF tests. The center performance is great straight from f/2.8 till about f/8. However, the borders/corners are rather soft at large apertures. They improve to good level at f/5.6 but the generally very good performance peak is not reached prior of f/8-f/11. This is very "late" for a prime lens and the figures aren't all that impressive.

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)

Chromatic aberrations (color shadows at harsh contrast transitions) are low at around 0.7px on the average at the image borders. This is usually not field relevant anymore.

Verdict

As a German website we'd love to report that we've seen another great Zeiss lens (home, sweet home after all) but at the end of the day the proof is in the pudding (or maybe in the "Kraut" here) and it just doesn't taste good. The Zeiss Distagon T* 25mm f/2.8 ZF performed pretty good in our Nikon APS-C review but it didn't impress during our full format tests. The resolution capabilities are simply sub-standard for such an expensive prime lens (@ ~800EUR/US$). The border quality is quite poor at large aperture settings. Same goes for the heavy vignetting problems here. The situation improves at medium apertures but the quality remains comparatively moderate. Lateral CAs are fairly low which helps a bit in terms of subjective quality perception. The amount of barrel distortion is about average for a prime lens in this class. The Zeiss lens is capable of focusing down to just 17cm (min. object to front element distance: 6cm) which is a fairly unique feature in an 28mm lens so if macro photography is your thing you may find this a useful aspect. The build quality is great, of course, but who wants a Mercedes with a Lada motor ? So I'm sorry to say ... not recommended.

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