Canon EF 100mm f/2.8 USM macro - (APS-C) Review / Test Report - Analysis
Lens Reviews - Canon EOS (APS-C)
Article Index
Introduction
Analysis

Distortion

Typical for prime lenses and especially for a macro lens the level of distortion is absolutely negligible.

Vignetting

The 100mm f/2.8 macro is a full format lens so it enjoys a sweet spot advantage when used on APS-C DSLRs. At f/2.8 it produces a medium degree of vignetting (~0.6EV) which is only visible in very critical scenes. The problem is basically irrelevant from f/4 onwards.

MTF (resolution)

The EF 100mm f/2.8 USM macro produced impressive MTF figures in the resolution lab. The lens is already capable of delivering an excellent (just) center performance at f/2.8 followed by very good borders/corners. The peak performance is reached between around f/5.6 with an excellent quality across the frame. The lens remains perfectly usable till about f/16. At f/22 diffraction effects have a rather drastic impact on the performance so this setting should be avoided on APS-C DSLRs - this is a physical limitation and not a design problem.

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 low and really nothing to worry about in field conditions.

Bokeh

The bokeh (the quality of the out-of-focus blur) is a primary aspect for a macro lens and the Canon lens is a good performer here. Out-of-focus highlights are very uniform and perfectly circular at f/2.8. The highlights deteriorate a little when stopping down - upon closer observation you can spot some small traces of outlining at f/5.6. The critical focus transition zones are decently rendered but not as as smooth as on the 100mm L lens for instance.

Bokeh Fringing / Longitudinal Chromatic Aberrations (LoCA)

Bokeh fringing is a problem which is present in most large aperture lenses but the EF 100mm f/2.8 performs better than most here. At f/2.8 there's a bit of fringing visible but it's not overly significant - if you observe the provided sample crops (f/2.8) below you may be able to spot traces of green (rear) & purple (front) halos in the focus transition zones. However, the problem is already very hard to spot at f/4 and it's basically gone by f/5.6.

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 Canon EF 100mm f/2.8 USM macro may be a comparatively old lens by now but it's still capable of playing in the top league - easily. It provides sharp images straight from f/2.8 and it's downright excellent between f/4 and f/8. Diffraction effects reduces the performance thereafter but it's fine to use all the way down to f/16. Neither distortions nor lateral CAs are something to worry about. Thanks to its full format design it produces only a medium degree of vignetting at f/2.8 when used on APS-C DSLRs. The amount of LoCAs (bokeh fringing) is comparatively moderate even at f/2.8. The quality of the bokeh (out-of-focus blur) is pretty good although not perfect.

The Canon lens features a true IF (internal focusing) mechanism so its physical length remains constant regardless of the focus setting - in terms of long term durability this is clearly a superior approach compared to the usual extension system used in third party lenses. The principal build quality leaves also nothing to be desired for a lens in this class. The implementation of the USM (ultrasonic AF) is excellent - compared to conventional macro lenses in this range it is a speed daemon here and a near silent one.

All-in-all highly recommended for APS-C EOS DSLRs!

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